Pharmaceutical Process Validation

A Series of Textbooks and Monographs
1. Pharmacokmetics, Milo Gibaldi and Donald Perrier
2. Good Manufacturing Practices for Pharmaceuticals: A Plan for Total
Quality Control, Sidney H. Willig, Murray M. Tuckerman, and William
S. Hitchings IV
3. Microencapsulation, edited by J. R Nixon
4. Drug Metabolism. Chemical and Biochemical Aspects, Bernard Testa
and Peter Jenner
5. New Drugs: Discovery and Development, edited by Alan A. Rubin
6. Sustained and Controlled Release Drug Delivery Systems, edited by
Joseph R. Robinson
7. Modern Pharmaceutics, edited by Gilbert S. Banker and Christopher
T. Rhodes
8. Prescription Drugs in Short Supply Case Histories, Michael A.
Schwartz
9. Activated Charcoal' Antidotal and Other Medical Uses, David O.
Cooney
10. Concepts in Drug Metabolism (in two parts), edited by Peter Jenner
and Bernard Testa
11. Pharmaceutical Analysis: Modern Methods (in two parts), edited by
James W, Munson
12. Techniques of Solubilization of Drugs, edited by Samuel H Yalkowsky
13. Orphan Drugs, edited by Fred E. Karch
14. Novel Drug Delivery Systems: Fundamentals, Developmental Concepts,
Biomedical Assessments, Yie W. Chien
15. Pharmacokmetics: Second Edition, Revised and Expanded, Milo
Gibaldi and Donald Perrier
16 Good Manufacturing Practices for Pharmaceuticals' A Plan for Total
Quality Control, Second Edition, Revised and Expanded, Sidney H
Willig, Murray M Tuckerman, and William S. Hitchings IV
17 Formulation of Veterinary Dosage Forms, edited by Jack Blodinger
18 Dermatological Formulations. Percutaneous Absorption, Brian W
Barry
19. The Clinical Research Process in the Pharmaceutical Industry, edited
by Gary M. Matoren
20. Microencapsulation and Related Drug Processes, Patrick B. Deasy
21. Drugs and Nutrients The Interactive Effects, edited by Daphne A.
Roe and T. Colin Campbell
22. Biotechnology of Industrial Antibiotics, Enck J. Vandamme
Copyright © 2003 Marcel Dekker, Inc.
23 Pharmaceutical Process Validation, edited by Bernard T Loftus and
Robert A Nash
24 Anticancer and Interferon Agents Synthesis and Properties, edited by
Raphael M Ottenbrtte and George B Butler
25 Pharmaceutical Statistics Practical and Clinical Applications, Sanford
Bolton
26 Drug Dynamics for Analytical, Clinical, and Biological Chemists,
Benjamin J Gudzmowicz, Burrows T Younkm, Jr, and Michael J
Gudzmowicz
27 Modern Analysis of Antibiotics, edited by Adjoran Aszalos
28 Solubility and Related Properties, Kenneth C James
29 Controlled Drug Delivery Fundamentals and Applications, Second
Edition, Revised and Expanded, edited by Joseph R Robinson and
Vincent H Lee
30 New Drug Approval Process Clinical and Regulatory Management,
edited by Richard A Guarino
31 Transdermal Controlled Systemic Medications, edited by Yie W Chien
32 Drug Delivery Devices Fundamentals and Applications, edited by
Praveen Tyle
33 Pharmacokinetics Regulatory • Industrial • Academic Perspectives,
edited by Peter G Welling and Francis L S Tse
34 Clinical Drug Trials and Tribulations, edited by Alien E Cato
35 Transdermal Drug Delivery Developmental Issues and Research Initiatives,
edited by Jonathan Hadgraft and Richard H Guy
36 Aqueous Polymeric Coatings for Pharmaceutical Dosage Forms,
edited by James W McGmity
37 Pharmaceutical Pelletization Technology, edited by Isaac Ghebre-
Sellassie
38 Good Laboratory Practice Regulations, edited by Alien F Hirsch
39 Nasal Systemic Drug Delivery, Yie W Chien, Kenneth S E Su, and
Shyi-Feu Chang
40 Modern Pharmaceutics Second Edition, Revised and Expanded,
edited by Gilbert S Banker and Chnstopher T Rhodes
41 Specialized Drug Delivery Systems Manufacturing and Production
Technology, edited by Praveen Tyle
42 Topical Drug Delivery Formulations, edited by David W Osborne and
Anton H Amann
43 Drug Stability Principles and Practices, Jens T Carstensen
44 Pharmaceutical Statistics Practical and Clinical Applications, Second
Edition, Revised and Expanded, Sanford Bolton
45 Biodegradable Polymers as Drug Delivery Systems, edited by Mark
Chasm and Robert Langer
46 Preclmical Drug Disposition A Laboratory Handbook, Francis L S
Tse and James J Jaffe
47 HPLC in the Pharmaceutical Industry, edited by Godwin W Fong and
Stanley K Lam
48 Pharmaceutical Bioequivalence, edited by Peter G Welling, Francis L
S Tse, and Shrikant V Dinghe
Copyright © 2003 Marcel Dekker, Inc.
49. Pharmaceutical Dissolution Testing, Umesh V. Sana/car
50. Novel Drug Delivery Systems: Second Edition, Revised and
Expanded, Yie W. Chien
51. Managing the Clinical Drug Development Process, David M. Cocchetto
and Ronald V. Nardi
52. Good Manufacturing Practices for Pharmaceuticals: A Plan for Total
Quality Control, Third Edition, edited by Sidney H. Willig and James
R. Stoker
53. Prodrugs: Topical and Ocular Drug Delivery, edited by Kenneth B.
Sloan
54. Pharmaceutical Inhalation Aerosol Technology, edited by Anthony J.
Mickey
55. Radiopharmaceuticals: Chemistry and Pharmacology, edited by
Adrian D. Nunn
56. New Drug Approval Process: Second Edition, Revised and Expanded,
edited by Richard A. Guarino
57. Pharmaceutical Process Validation: Second Edition, Revised and Expanded,
edited by Ira R. Berry and Robert A. Nash
58. Ophthalmic Drug Delivery Systems, edited byAshim K. Mitra
59. Pharmaceutical Skin Penetration Enhancement, edited by Kenneth A.
Walters and Jonathan Hadgraft
60. Colonic Drug Absorption and Metabolism, edited by Peter R. Bieck
61. Pharmaceutical Particulate Carriers1 Therapeutic Applications, edited
by Alain Rolland
62. Drug Permeation Enhancement: Theory and Applications, edited by
Dean S. Hsieh
63. Glycopeptide Antibiotics, edited by Ramakrishnan Nagarajan
64. Achieving Sterility in Medical and Pharmaceutical Products, Nigel A.
Halls
65. Multiparticulate Oral Drug Delivery, edited by Isaac Ghebre-Sellassie
66. Colloidal Drug Delivery Systems, edited byJorg Kreuter
67 Pharmacokinetics: Regulatory • Industrial • Academic Perspectives,
Second Edition, edited by Peter G. Welling and Francis L. S. Tse
68. Drug Stability: Principles and Practices, Second Edition, Revised and
Expanded, Jens T. Carstensen
69. Good Laboratory Practice Regulations: Second Edition, Revised and
Expanded, edited by Sandy Weinberg
70. Physical Characterization of Pharmaceutical Solids, edited by Harry
G. Bnttain
71. Pharmaceutical Powder Compaction Technology, edited by Goran Alderborn
and Christer Nystrom
72. Modern Pharmaceutics. Third Edition, Revised and Expanded, edited
by Gilbert S. Banker and Christopher J Rhodes
73. Microencapsulation. Methods and Industrial Applications, edited by
Simon Benita
74. Oral Mucosal Drug Delivery, edited by Michael J. Rathbone
75. Clinical Research in Pharmaceutical Development, edited by Barry
Bleidt and Michael Montagne
Copyright © 2003 Marcel Dekker, Inc.
76 The Drug Development Process Increasing Efficiency and Cost Effectiveness,
edited by Peter G Welling, Louis Lasagna, and Umesh
V Banakar
77 Microparticulate Systems for the Delivery of Proteins and Vaccines,
edited by Smadar Cohen and Howard Bernstein
78 Good Manufacturing Practices for Pharmaceuticals A Plan for Total
Quality Control, Fourth Edition, Revised and Expanded, Sidney H
Willig and James R Stoker
79 Aqueous Polymeric Coatings for Pharmaceutical Dosage Forms
Second Edition, Revised and Expanded, edited by James W
McGmity
80 Pharmaceutical Statistics Practical and Clinical Applications, Third
Edition, Sanford Bolton
81 Handbook of Pharmaceutical Granulation Technology edited by Dilip
M Pankh
82 Biotechnology of Antibiotics Second Edition, Revised and Expanded,
edited by William R Strohl
83 Mechanisms of Transdermal Drug Delivery, edited by Russell O Potts
and Richard H Guy
84 Pharmaceutical Enzymes edited by Albert Lauwers and Simon
Scharpe
85 Development of Biopharmaceutical Parenteral Dosage Forms, edited
by John A Bontempo
86 Pharmaceutical Project Management, edited by Tony Kennedy
87 Drug Products for Clinical Trials An International Guide to Formulation
• Production • Quality Control, edited by Donald C Monkhouse
and Christopher T Rhodes
88 Development and Formulation of Veterinary Dosage Forms Second
Edition, Revised and Expanded, edited by Gregory E Hardee and J
Desmond Baggot
89 Receptor-Based Drug Design, edited by Paul Leff
90 Automation and Validation of Information in Pharmaceutical Processing,
edited by Joseph F deSpautz
91 Dermal Absorption and Toxicity Assessment, edited by Michael S
Roberts and Kenneth A Walters
92 Pharmaceutical Experimental Design, Gareth A Lewis, Didier
Mathieu, and Roger Phan-Tan-Luu
93 Preparing for FDA Pre-Approval Inspections, edited by Martin D
Hynes III
94 Pharmaceutical Excipients Characterization by IR, Raman, and NMR
Spectroscopy, David E Bugay and W Paul Fmdlay
95 Polymorphism in Pharmaceutical Solids, edited by Harry G Brittam
96 Freeze-Drymg/Lyophihzation of Pharmaceutical and Biological Products,
edited by Louis Rey and Joan C May
97 Percutaneous Absorption Drugs-Cosmetics-Mechanisms-Methodology,
Third Edition, Revised and Expanded, edited by Robert L
Bronaugh and Howard I Maibach
Copyright © 2003 Marcel Dekker, Inc.
98. Bioadhesive Drug Delivery Systems: Fundamentals, Novel Approaches,
and Development, edited by Edith Mathiowitz, Donald E.
Chtckering III, and Claus-Michael Lehr
99. Protein Formulation and Delivery, edited by Eugene J. McNally
100. New Drug Approval Process: Third Edition, The Global Challenge,
edited by Richard A. Guarino
101. Peptide and Protein Drug Analysis, edited by Ronald E. Reid
102 Transport Processes in Pharmaceutical Systems, edited by Gordon L
Amidon, Ping I. Lee, and Elizabeth M. Topp
103. Excipient Toxicity and Safety, edited by Myra L. Weiner and Lois A.
Kotkoskie
104 The Clinical Audit in Pharmaceutical Development, edited by Michael
R. Hamrell
105. Pharmaceutical Emulsions and Suspensions, edited by Francoise
Nielloud and Gilberte Marti-Mestres
106. Oral Drug Absorption: Prediction and Assessment, edited by Jennifer B.
Dressman and Hans Lennernas
107. Drug Stability: Principles and Practices, Third Edition, Revised and
Expanded, edited by Jens T. Carstensen and C. T. Rhodes
108. Containment in the Pharmaceutical Industry, edited by James P.
Wood
109. Good Manufacturing Practices for Pharmaceuticals: A Plan for Total
Quality Control from Manufacturer to Consumer, Fifth Edition, Revised
and Expanded, Sidney H Willig
110. Advanced Pharmaceutical Solids, Jens T Carstensen
111. Endotoxins: Pyrogens, LAL Testing, and Depyrogenation, Second
Edition, Revised and Expanded, Kevin L. Williams
112 Pharmaceutical Process Engineering, Anthony J. Hickey and David
Ganderton
113. Pharmacogenomics, edited by Werner Kalow, Urs A. Meyer, and Rachel
F. Tyndale
114. Handbook of Drug Screening, edited by Ramaknshna Seethala and
Prabhavathi B. Fernandas
115. Drug Targeting Technology: Physical • Chemical • Biological Methods,
edited by Hans Schreier
116. Drug-Drug Interactions, edited by A. David Rodngues
117. Handbook of Pharmaceutical Analysis, edited by Lena Ohannesian
and Anthony J. Streeter
118. Pharmaceutical Process Scale-Up, edited by Michael Levin
119. Dermatological and Transdermal Formulations, edited by Kenneth A.
Walters
120. Clinical Drug Trials and Tribulations: Second Edition, Revised and
Expanded, edited by Alien Cato, Lynda Sutton, and Alien Cato III
121. Modern Pharmaceutics: Fourth Edition, Revised and Expanded, edited
by Gilbert S. Banker and Chnstopher T. Rhodes
122. Surfactants and Polymers in Drug Delivery, Martin Malmsten
123. Transdermal Drug Delivery: Second Edition, Revised and Expanded,
124. Good Laboratory Practice Regulations: Second Edition, Revised and
Expanded, edited by Sandy Weinberg
125. Parenteral Quality Control: Sterility, Pyrogen, Particulate, and Package
Integrity Testing. Third Edition, Revised and Expanded, Michael
J. Akers, Daniel S. Larnmore, and Dana Morion Guazzo
126. Modified-Release Drug Delivery Technology, edited by Michael J.
Rathbone, Jonathan Hadgraft, and Michael S. Roberts
127. Simulation for Designing Clinical Trials' A Pharmacokinetic-Pharmacodynamic
Modeling Perspective, edited by Hui C Kimko and Stephen
B Duffull
128. Affinity Capillary Electrophoresis in Pharmaceutics and Biopharmaceutics,
edited by Remhard H. H. Neubert and Hans-Hermann Ruttinger
129. Pharmaceutical Process Validation: An International Third Edition, Revised
and Expanded, edited by Robert A Nash and Alfred H. Wachter
130. Ophthalmic Drug Delivery Systems: Second Edition, Revised and Expanded,
edited byAshim K. Mitra
131 Pharmaceutical Gene Delivery Systems, edited by Alam Rolland and
Sean M. Sullivan
ADDITIONAL VOLUMES IN PREPARATION
Biomarkers in Clinical Drug Development, edited by John C Bloom
and Robert A. Dean
Pharmaceutical Inhalation Aerosol Technology: Second Edition, Revised
and Expanded, edited by Anthony J Mickey
Pharmaceutical Extrusion Technology, edited by Isaac Ghebre-Sellassie
and Charles Martin
Pharmaceutical Compliance, edited by Carmen Medina
Copyright © 2003 Marcel Dekker, Inc.
Dedicated to Theodore E. Byers, formerly of the U.S. Food and Drug
Administration, and Heinz Sucker, Professor at the University of Berne,
Switzerland, for their pioneering contributions with respect to
the pharmaceutical process validation concept. We also acknowledge
the past contributions of Bernard T. Loftus and Ira R. Berry toward the
success of Pharmaceutical Process Validation.
Copyright © 2003 Marcel Dekker, Inc.

Preface
The third edition of Pharmaceutical Process Validation represents a new approach
to the topic in several important respects.
Many of us in the field had made the assumption that pharmaceutical
process validation was an American invention, based on the pioneering work of
Theodore E. Byers and Bernard T. Loftus, both formerly with the U.S. Food &
Drug Administration. The truth is that many of our fundamental concepts of
pharmaceutical process validation came to us from “Validation of Manufacturing
Processes,” Fourth European Seminar on Quality Control, September 25,
1980, Geneva, Switzerland, and Validation in Practice, edited by H. Sucker,
Wissenschaftliche Verlagsegesellschaft, GmbH, Stuttgard, Germany, 1983.
There are new chapters in this edition that will add to the book’s impact.
They include “Validation for Medical Devices” by Nishihata, “Validation of
Biotechnology Processes” by Sofer, “Transdermal Process Validation” by Neal,
“Integrated Packaging Validation” by Frederick, “Statistical Methods for Uniformity
and Dissolution Testing” by Bergum and Utter, “Change Control and
SUPAC” by Waterland and Kowtna, “Validation in Contract Manufacturing”
by Parikh, and “Harmonization, GMPs, and Validation” by Wachter.
I am pleased to have Dr. Alfred Wachter join me as coeditor of this edition.
He was formerly head of Pharmaceutical Product Development for the
CIBA Pharmaceutical Company in Basel, Switzerland, and also spent a number
of years on assignment in Asia for CIBA. Fred brings a very strong international
perspective to the subject matter.
Robert A. Nash
Copyright © 2003 Marcel Dekker, Inc.
Contents

Preface
Contributors
Introduction
1. Regulatory Basis for Process Validation
John M. Dietrick and Bernard T. Loftus
2. Prospective Process Validation
Allen Y. Chao, F. St. John Forbes, Reginald F. Johnson,
and Paul Von Doehren
3. Retrospective Validation
Chester J. Trubinski
4. Sterilization Validation
Michael J. Akers and Neil R. Anderson
5. Validation of Solid Dosage Forms
Jeffrey S. Rudolph and Robert J. Sepelyak
6. Validation for Medical Devices
Toshiaki Nishihata
7. Validation of Biotechnology Processes
Gail Sofer
8. Transdermal Process Validation
Charlie Neal, Jr.
9. Validation of Lyophilization
Edward H. Trappler
Copyright © 2003 Marcel Dekker, Inc.
10. Validation of Inhalation Aerosols
Christopher J. Sciarra and John J. Sciarra
11. Process Validation of Pharmaceutical Ingredients
Robert A. Nash
12. Qualification of Water and Air Handling Systems
Kunio Kawamura
13. Equipment and Facility Qualification
Thomas L. Peither
14. Validation and Verification of Cleaning Processes
William E. Hall
15. Validation of Analytical Methods and Processes
Ludwig Huber
16. Computer System Validation:
Controlling the Manufacturing Process
Tony de Claire
17. Integrated Packaging Validation
Mervyn J. Frederick
18. Analysis of Retrospective Production Data Using
Quality Control Charts
Peter H. Cheng and John E. Dutt
19. Statistical Methods for Uniformity and Dissolution Testing
James S. Bergum and Merlin L. Utter
20. Change Control and SUPAC
Nellie Helen Waterland and Christopher C. Kowtna
21. Process Validation and Quality Assurance
Carl B. Rifino
22. Validation in Contract Manufacturing
Dilip M. Parikh
23. Terminology of Nonaseptic Process Validation
Kenneth G. Chapman
24. Harmonization, GMPs, and Validation
Alfred H. Wachter
Copyright © 2003 Marcel Dekker, Inc.
Contributors
Michael J. Akers Baxter Pharmaceutical Solutions, Bloomington, Indiana,
U.S.A.
Neil R. Anderson Eli Lilly and Company, Indianapolis, Indiana, U.S.A.
James S. Bergum Bristol-Myers Squibb Company, New Brunswick, New Jersey,
U.S.A.
Kenneth G. Chapman Drumbeat Dimensions, Inc., Mystic, Connecticut,
U.S.A.
Allen Y. Chao Watson Labs, Carona, California, U.S.A.
Peter H. Cheng New York State Research Foundation for Mental Hygiene,
New York, New York, U.S.A.
Tony de Claire APDC Consulting, West Sussex, England
John M. Dietrick Center for Drug Evaluation and Research, U.S. Food and
Drug Administration, Rockville, Maryland, U.S.A.
John E. Dutt EM Industries, Inc., Hawthorne, New York, U.S.A.
Mervyn J. Frederick NV Organon–Akzo Nobel, Oss, The Netherlands
William E. Hall Hall & Pharmaceutical Associates, Inc., Kure Beach, North
Carolina, U.S.A.
Ludwig Huber Agilent Technologies GmbH, Waldbronn, Germany
Copyright © 2003 Marcel Dekker, Inc.
F. St. John Forbes Wyeth Labs, Pearl River, New York, U.S.A.
*Reginald F. Johnson Searle & Co., Inc., Skokie, Illinois, U.S.A.
Kunio Kawamura Otsuka Pharmaceutical Co., Ltd., Tokushima, Japan
Christopher C. Kowtna DuPont Pharmaceuticals Co., Wilmington, Delaware,
U.S.A.
*Bernard T. Loftus Bureau of Drugs, U.S. Food and Drug Administration,
Washington, D.C., U.S.A.
Robert A. Nash Stevens Institute of Technology, Hoboken, New Jersey,
U.S.A.
Charlie Neal, Jr. Diosynth-RTP, Research Triangle Park, North Carolina,
U.S.A.
Toshiaki Nishihata Santen Pharmaceutical Co., Ltd., Osaka, Japan
Dilip M. Parikh APACE PHARMA Inc., Westminster, Maryland, U.S.A.
Thomas L. Peither PECON—Peither Consulting, Schopfheim, Germany
Carl B. Rifino AstraZeneca Pharmaceuticals LP, Newark, Delaware, U.S.A.
Jeffrey S. Rudolph Pharmaceutical Consultant, St. Augustine, Florida, U.S.A.
Christopher J. Sciarra Sciarra Laboratories Inc., Hicksville, New York, U.S.A.
John J. Sciarra Sciarra Laboratories Inc., Hicksville, New York, U.S.A.
Robert J. Sepelyak AstraZeneca Pharmaceuticals LP, Wilmington, Delaware,
U.S.A.
Gail Sofer BioReliance, Rockville, Maryland, U.S.A.
Edward H. Trappler Lyophilization Technology, Inc., Warwick, Pennsylvania,
U.S.A.
*Retired
Copyright © 2003 Marcel Dekker, Inc.
Chester J. Trubinski Church & Dwight Co., Inc., Princeton, New Jersey,
U.S.A.
Merlin L. Utter Wyeth Pharmaceuticals, Pearl River, New York, U.S.A.
Paul Von Doehren Searle & Co., Inc., Skokie, Illinois, U.S.A.
Alfred H. Wachter Wachter Pharma Projects, Therwil, Switzerland
Nellie Helen Waterland DuPont Pharmaceuticals Co., Wilmington, Delaware,
U.S.A.
Copyright © 2003 Marcel Dekker, Inc.
Introduction
Robert A. Nash
Stevens Institute of Technology, Hoboken, New Jersey, U.S.A.
I. FDA GUIDELINES
The U.S. Food and Drug Administration (FDA) has proposed guidelines with
the following definition for process validation [1]:
Process validation is establishing documented evidence which provides a
high degree of assurance that a specific process (such as the manufacture
of pharmaceutical dosage forms) will consistently produce a product meeting
its predetermined specifications and quality characteristics.
According to the FDA, assurance of product quality is derived from careful
and systemic attention to a number of important factors, including: selection
of quality components and materials, adequate product and process design, and
(statistical) control of the process through in-process and end-product testing.
Thus, it is through careful design (qualification) and validation of both the
process and its control systems that a high degree of confidence can be established
that all individual manufactured units of a given batch or succession of
batches that meet specifications will be acceptable.
According to the FDA’s Current Good Manufacturing Practices (CGMPs)
21CFR 211.110 a:
Control procedures shall be established to monitor output and to validate
performance of the manufacturing processes that may be responsible for
causing variability in the characteristics of in-process material and the drug
product. Such control procedures shall include, but are not limited to the
following, where appropriate [2]:
1. Tablet or capsule weight variation
2. Disintegration time
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3. Adequacy of mixing to assure uniformity and homogeneity
4. Dissolution time and rate
5. Clarity, completeness, or pH of solutions
The first four items listed above are directly related to the manufacture
and validation of solid dosage forms. Items 1 and 3 are normally associated
with variability in the manufacturing process, while items 2 and 4 are usually
influenced by the selection of the ingredients in the product formulation. With
respect to content uniformity and unit potency control (item 3), adequacy of
mixing to assure uniformity and homogeneity is considered a high-priority concern.
Conventional quality control procedures for finished product testing encompass
three basic steps:
1. Establishment of specifications and performance characteristics
2. Selection of appropriate methodology, equipment, and instrumentation
to ensure that testing of the product meets specifications
3. Testing of the final product, using validated analytical and testing
methods to ensure that finished product meets specifications.
With the emergence of the pharmaceutical process validation concept, the following
four additional steps have been added:
4. Qualification of the processing facility and its equipment
5. Qualification and validation of the manufacturing process through appropriate
means
6. Auditing, monitoring, sampling, or challenging the key steps in the
process for conformance to in-process and final product specifications
7. Revalidation when there is a significant change in either the product
or its manufacturing process [3].
II. TOTAL APPROACH TO PHARMACEUTICAL
PROCESS VALIDATION
It has been said that there is no specific basis for requiring a separate set of
process validation guidelines, since the essentials of process validation are embodied
within the purpose and scope of the present CGMP regulations [2]. With
this in mind, the entire CGMP document, from subpart B through subpart K,
may be viewed as being a set of principles applicable to the overall process of
manufacturing, i.e., medical devices (21 CFR–Part 820) as well as drug products,
and thus may be subjected, subpart by subpart, to the application of the
principles of qualification, validation, verification and control, in addition to
change control and revalidation, where applicable. Although not a specific re-
Copyright © 2003 Marcel Dekker, Inc.
quirement of current regulations, such a comprehensive approach with respect
to each subpart of the CGMP document has been adopted by many drug firms.
A checklist of qualification and control documentation with respect to
CGMPs is provided in Table 1. A number of these topics are discussed separately
in other chapters of this book.
III. WHY ENFORCE PROCESS VALIDATION?
The FDA, under the authority of existing CGMP regulations, guidelines [1], and
directives [3], considers process validation necessary because it makes good
engineering sense. The basic concept, according to Mead [5], has long been
Table 1 Checklist of Qualification and Control Documentation
Qualification and
Subpart Section of CGMPs control documentation
A General provisions
B Organization and personnel Responsibilities of the quality control
unit
C Buildings and facilities Plant and facility installation and
qualification
Maintenance and sanitation
Microbial and pest control
D Equipment Installation and qualification of
equipment and cleaning methods
E Control of components, containers Incoming component testing proceand
closures dures
F Production and process controls Process control systems, reprocessing
control of microbial contamination
G Packaging and labeling controls Depyrogenation, sterile packaging,
filling and closing, expire dating
H Holding and distribution Warehousing and distribution procedures
I Laboratory controls Analytical methods, testing for release
component testing and stability
testing
J Records and reports Computer systems and information
systems
K Return and salvaged drug products Batch reprocessing
Sterilization procedures, Air and water quality are covered in appropriate subparts of Table 1.
Copyright © 2003 Marcel Dekker, Inc.
applied in other industries, often without formal recognition that such a concept
was being used. For example, the terms reliability engineering and qualification
have been used in the past by the automotive and aerospace industries to represent
the process validation concept.
The application of process validation should result in fewer product recalls
and troubleshooting assignments in manufacturing operations and more
technically and economically sound products and their manufacturing processes.
In the old days R & D “gurus” would literally hand down the “go” sometimes
overformulated product and accompanying obtuse manufacturing procedure,
usually with little or no justification or rationale provided. Today, under FDA’s
Preapproval Inspection (PAI) program [4] such actions are no longer acceptable.
The watchword is to provide scientifically sound justifications (including
qualification and validation documentation) for everything that comes out of the
pharmaceutical R & D function.
IV. WHAT IS PROCESS VALIDATION?
Unfortunately, there is still much confusion as to what process validation is
and what constitutes process validation documentation. At the beginning of this
introduction several different definitions for process validation were provided,
which were taken from FDA guidelines and the CGMPs. Chapman calls process
validation simply “organized, documented common sense” [6]. Others have said
that “it is more than three good manufactured batches” and should represent a
lifetime commitment as long as the product is in production, which is pretty
much analogous to the retrospective process validation concept.
The big problem is that we use the term validation generically to cover
the entire spectrum of CGMP concerns, most of which are essentially people,
equipment, component, facility, methods, and procedural qualification. The specific
term process validation should be reserved for the final stage(s) of the
product/process development sequence. The essential or key steps or stages of
a successfully completed product/process development program are presented
in Table 2 [7].
The end of the sequence that has been assigned to process validation is
derived from the fact that the specific exercise of process validation should
never be designed to fail. Failure in carrying out the process validation assignment
is often the result of incomplete or faulty understanding of the process’s
capability, in other words, what the process can and cannot do under a given
set of operational circumstances. In a well-designed, well-run overall validation
program, most of the budget dollars should be spent on equipment, component,
facility, methods qualification, and process demonstration, formerly called process
qualification. In such a program, the formalized final process validation
Copyright © 2003 Marcel Dekker, Inc.
Table 2 The Key Stages in the Product/Process
Development Sequence
Development stage Pilot scale-up phase
Product design 1 ? batch size
Product characterization
Product selection (“go” formula)
Process design
Product optimization 10 ? batch size
Process characterization
Process optimization
Process demonstration 100 ? batch size
Process validation program
Product/process certification
With the exception of solution products, the bulk of the work is normally
carried out at 10 ? batch size, which is usually the first scale-up
batches in production-type equipment.
sequence provides only the necessary process validation documentation required
by the regulatory authorities—in other words, the “Good Housekeeping Seal of
Approval,” which shows that the manufacturing process is in a state of control.
Such a strategy is consistent with the U.S. FDA’s preapproval inspection
program [4], wherein the applicant firm under either a New Drug Application
(NDA) or an Abbreviated New Drug Application (ANDA) submission must
show the necessary CGMP information and qualification data (including appropriate
development reports), together with the formal protocol for the forthcoming
full-scale, formal process validation runs required prior to product launch.
Again, the term validation has both a specific meaning and a general one,
depending on whether the word “process” is used. Determine during the course
of your reading whether the entire concept is discussed in connection with the
topic—i.e., design, characterization, optimization, qualification, validation, and/
or revalidation—or whether the author has concentrated on the specifics of the
validation of a given product and/or its manufacturing process. In this way the
text will take on greater meaning and clarity.
V. PILOT SCALE-UP AND PROCESS VALIDATION
The following operations are normally carried out by the development function
prior to the preparation of the first pilot-production batch. The development
activities are listed as follows:
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1. Formulation design, selection, and optimization
2. Preparation of the first pilot-laboratory batch
3. Conduct initial accelerated stability testing
4. If the formulation is deemed stable, preparation of additional pilotlaboratory
batches of the drug product for expanded nonclinical and/
or clinical use.
The pilot program is defined as the scale-up operations conducted subsequent
to the product and its process leaving the development laboratory and
prior to its acceptance by the full scale manufacturing unit. For the pilot program
to be successful, elements of process validation must be included and completed
during the developmental or pilot laboratory phase of the work.
Thus, product and process scale-up should proceed in graduated steps with
elements of process validation (such as qualifications) incorporated at each stage
of the piloting program [9,10].
A. Laboratory Batch
The first step in the scale-up process is the selection of a suitable preliminary
formula for more critical study and testing based on certain agreed-upon initial
design criteria, requirements, and/or specifications. The work is performed in
the development laboratory. The formula selected is designated as the (1 ? )
laboratory batch. The size of the (1 ? ) laboratory batch is usually 3–10 kg of a
solid or semisolid, 3–10 liters of a liquid, or 3000 to 10,000 units of a tablet or
capsule.
B. Laboratory Pilot Batch
After the (1 ? ) laboratory batch is determined to be both physically and chemically
stable based on accelerated, elevated temperature testing (e.g., 1 month at
45°C or 3 months at 40°C or 40°C/80% RH), the next step in the scale-up
process is the preparation of the (10 ? ) laboratory pilot batch. The (10 ? )
laboratory pilot batch represents the first replicated scale-up of the designated
formula. The size of the laboratory pilot batch is usually 30–100 kg, 30–100
liters, or 30,000 to 100,000 units.
It is usually prepared in small pilot equipment within a designated CGMPapproved
area of the development laboratory. The number and actual size of the
laboratory pilot batches may vary in response to one or more of the following
factors:
1. Equipment availability
2. Active pharmaceutical ingredient (API)
Copyright © 2003 Marcel Dekker, Inc.
3. Cost of raw materials
4. Inventory requirements for clinical and nonclinical studies
Process demonstration or process capability studies are usually started in this
important second stage of the pilot program. Such capability studies consist of
process ranging, process characterization, and process optimization as a prerequisite
to the more formal validation program that follows later in the piloting
sequence.
C. Pilot Production
The pilot-production phase may be carried out either as a shared responsibility
between the development laboratories and its appropriate manufacturing counterpart
or as a process demonstration by a separate, designated pilot-plant or
process-development function. The two organization piloting options are presented
separately in Figure 1. The creation of a separate pilot-plant or processdevelopment
unit has been favored in recent years because it is ideally suited to
carry out process scale-up and/or validation assignments in a timely manner. On
the other hand, the joint pilot-operation option provides direct communication
between the development laboratory and pharmaceutical production.
Figure 1 Main piloting options. (Top) Separate pilot plant functions—engineering
concept. (Bottom) Joint pilot operation.
Copyright © 2003 Marcel Dekker, Inc.
The object of the pilot-production batch is to scale the product and process
by another order of magnitude (100 ? ) to, for example, 300–1,000 kg, 300–
1,000 liters, or 300,000–1,000,000 dosage form units (tablets or capsules) in
size. For most drug products this represents a full production batch in standard
production equipment. If required, pharmaceutical production is capable of scaling
the product/process to even larger batch sizes should the product require
expanded production output. If the batch size changes significantly, additional
validation studies would be required. The term product/process is used, since
one can’t describe a product with discussing its process of manufacture and,
conversely, one can’t talk about a process without describing the product being
manufactured.
Usually large production batch scale-up is undertaken only after product
introduction. Again, the actual size of the pilot-production (100 ? ) batch may
vary due to equipment and raw material availability. The need for additional
pilot-production batches ultimately depends on the successful completion of a
first pilot batch and its process validation program. Usually three successfully
completed pilot-production batches are required for validation purposes.
In summary, process capability studies start in the development laboratories
and/or during product and process development, and continue in welldefined
stages until the process is validated in the pilot plant and/or pharmaceutical
production.
An approximate timetable for new product development and its pilot
scale-up program is suggested in Table 3.
VI. PROCESS VALIDATION: ORDER OF PRIORITY
Because of resource limitation, it is not always possible to validate an entire
company’s product line at once. With the obvious exception that a company’s
most profitable products should be given a higher priority, it is advisable to
draw up a list of product categories to be validated.
The following order of importance or priority with respect to validation is
suggested:
A. Sterile Products and Their Processes
1. Large-volume parenterals (LVPs)
2. Small-volume parenterals (SVPs)
3. Ophthalmics, other sterile products, and medical devices
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Table3 Approximate Timetable for New Product Development and Pilot
Scale-Up Trials
Calendar
Event months
Formula selection and development 2–4
Assay methods development and formula optimization 2–4
Stability in standard packaging 3-month readout (1 ? size) 3–4
Pilot-laboratory batches (10 ? size) 1–3
Preparation and release of clinical supplies (10 ? size) and
establishment of process demonstration 1–4
Additional stability testing in approved packaging 3–4
6–8-month readout (1 ? size)
3-month readout (10 ? size)
Validation protocols and pilot batch request 1–3
Pilot-production batches (100 ? size) 1–3
Additional stability testing in approved packaging 3–4
9–12-month readout (1 ? size)
6–8-month readout (10 ? size)
3-month readout (100 ? size)
Interim approved technical product development report with
approximately 12 months stability (1 ? size) 1–3
Totals 18–36
B. Nonsterile Products and Their Processes
1. Low-dose/high-potency tablets and capsules/transdermal delivery systems
(TDDs)
2. Drugs with stability problems
3. Other tablets and capsules
4. Oral liquids, topicals, and diagnostic aids
VII. WHO DOES PROCESS VALIDATION?
Process validation is done by individuals with the necessary training and experience
to carry out the assignment.
The specifics of how a dedicated group, team, or committee is organized
to conduct process validation assignments is beyond the scope of this introductory
chapter. The responsibilities that must be carried out and the organizational
structures best equipped to handle each assignment are outlined in Table 4. The
Copyright © 2003 Marcel Dekker, Inc.
Table 4 Specific Responsibilities of Each Organizational Structure within the Scope
of Process Validation
Engineering Install, qualify, and certify plant, facilities, equipment, and support
system.
Development Design and optimize manufacturing process within design limits,
specifications, and/or requirements—in other words, the establishment
of process capability information.
Manufacturing Operate and maintain plant, facilities, equipment, support systems,
and the specific manufacturing process within its design
limits, specifications, and/or requirements.
Quality assurance Establish approvable validation protocols and conduct process
validation by monitoring, sampling, testing, challenging, and/
or auditing the specific manufacturing process for compliance
with design limits, specifications, and/or requirements.
Source: Ref. 8.
best approach in carrying out the process validation assignment is to establish a
Chemistry, Manufacturing and Control (CMC) Coordination Committee at the
specific manufacturing plant site [10]. Representation on such an important logistical
committee should come from the following technical operations:
• Formulation development (usually a laboratory function)
• Process development (usually a pilot plant function)
• Pharmaceutical manufacturing (including packaging operations)
• Engineering (including automation and computer system responsibilities)
• Quality assurance
• Analytical methods development and/or Quality Control
• API Operations (representation from internal operations or contract
manufacturer)
• Regulatory Affairs (technical operations representative)
• IT (information technology) operations
The chairperson or secretary of such an important site CMC Coordination Committee
should include the manager of process validation operations. Typical
meeting agendas may include the following subjects in the following recommended
order of priority:
• Specific CGMP issues for discussion and action to be taken
• Qualification and validation issues with respect to a new product/process
Copyright © 2003 Marcel Dekker, Inc.
• Technology transfer issues within or between plant sites.
• Pre-approval inspection (PAI) issues of a forthcoming product/process
• Change control and scale-up, post approval changes (SUPAC) with
respect to current approved product/process [11].
VIII. PROCESS DESIGN AND CHARACTERIZATION
Process capability is defined as the studies used to determine the critical process
parameters or operating variables that influence process output and the range of
numerical data for critical process parameters that result in acceptable process
output. If the capability of a process is properly delineated, the process should
consistently stay within the defined limits of its critical process parameters and
product characteristics [12].
Process demonstration formerly called process qualification, represents
the actual studies or trials conducted to show that all systems, subsystems, or
unit operations of a manufacturing process perform as intended; that all critical
process parameters operate within their assigned control limits; and that such
studies and trials, which form the basis of process capability design and testing,
are verifiable and certifiable through appropriate documentation.
The manufacturing process is briefly defined as the ways and means used
to convert raw materials into a finished product. The ways and means also
include people, equipment, facilities, and support systems required to operate
the process in a planned and effectively managed way. All the latter functions
must be qualified individually. The master plan or protocol for process capability
design and testing is presented in Table 5.
A simple flow chart should be provided to show the logistical sequence
of unit operations during product/process manufacture. A typical flow chart used
in the manufacture of a tablet dosage form by the wet granulation method is
presented in Figure 2.
IX. STREAMLINING VALIDATION OPERATIONS
The best approach to avoiding needless and expensive technical delays is to
work in parallel. The key elements at this important stage of the overall process
are the API, analytical test methods, and the drug product (pharmaceutical dosage
form). An integrated and parallel way of getting these three vitally important
functions to work together is depicted in Figure 3.
Figure 3 shows that the use of a single analytical methods testing function
is an important technical bridge between the API and the drug product development
functions as the latter two move through the various stages of develop-
Copyright © 2003 Marcel Dekker, Inc.
Table5 Master Plan or Protocol for Process Capability Design and Testing
Objective Process capability design and testing
Types of process Batch, intermittent, continuous
Typical processes Chemical, pharmaceutical, biochemical
Process definition Flow diagram, in-process, finished product
Definition of process output Potency, yield, physical parameters
Definition of test methods Instrumentation, procedures, precision, and
accuracy
Process analysis Process variables, matrix design, factorial design
analysis
Pilot batch trials Define sampling and testing, stable, extended runs
Pilot batch replication Different days, different materials, different equipment
Process redefinition Reclassification of process variables
Process capability evaluation Stability and variability of process output, economic
limits
Final report Recommended SOP, specifications, and process
limits
Figure 2 Process flow diagram for the manufacture of a tablet dosage form by wet
granulation method. The arrows show the transfer of material into and out of each of the
various unit operations. The information in parentheses indicates additions of material to
specific unit operations. A list of useful pharmaceutical unit operations is presented in
Table 6.
Copyright © 2003 Marcel Dekker, Inc.
Table6 A List of Useful Pharmaceutical Unit Operations According to Categories
Heat transfer processes: Cooking, cooling, evaporating, freezing, heating, irradiating,
sterilizing, freeze-drying
Change in state: Crystallizing, dispersing, dissolving, immersing, freeze-drying, neutralizing
Change in size: Agglomerating, blending, coating, compacting, crushing, crystallizing,
densifying, emulsifying, extruding, flaking, flocculating, grinding, homogenizing,
milling, mixing, pelletizing, pressing, pulverizing, precipitating, sieving
Moisture transfer processes: Dehydrating, desiccating, evaporating, fluidizing, humidifying,
freeze-drying, washing, wetting
Separation processes: Centrifuging, clarifying, deareating, degassing, deodorizing, dialyzing,
exhausting, extracting, filtering, ion exchanging, pressing, sieving, sorting,
washing
Transfer processes: Conveying, filling, inspecting, pumping, sampling, storing, transporting,
weighing
Source: Ref. 13.
ment, clinical study, process development, and process validation and into production.
Working individually with separate analytical testing functions and
with little or no appropriate communication among these three vital functions is
a prescription for expensive delays. It is important to remember that the concept
illustrated in Figure 3 can still be followed even when the API is sourced from
outside the plant site or company. In this particular situation there will probably
be two separate analytical methods development functions: one for the API
manufacturer and one for the drug product manufacturer [14].
X. STATISTICAL PROCESS CONTROL AND
PROCESS VALIDATION
Statistical process control (SPC), also called statistical quality control and process
validation (PV), represents two sides of the same coin. SPC comprises the
various mathematical tools (histogram, scatter diagram run chart, and control
chart) used to monitor a manufacturing process and to keep it within in-process
and final product specification limits. Lord Kelvin once said, “When you can
measure what you are speaking about, and express it in numbers, then you know
something about it.” Such a thought provides the necessary link between the
two concepts. Thus, SPC represents the tools to be used, while PV represents
the procedural environment in which those tools are used.
Copyright © 2003 Marcel Dekker, Inc.
Figure 3 Working in parallel. (Courtesy of Austin Chemical Co., Inc.)
There are three ways of establishing quality products and their manufacturing
processes:
1. In-process and final product testing, which normally depends on sampling
size (the larger the better). In some instances, nothing short of
excessive sampling can ensure reaching the desired goal, i.e., sterility
testing.
2. Establishment of tighter (so called “in-house”) control limits that hold
the product and the manufacturing process to a more demanding stan-
Copyright © 2003 Marcel Dekker, Inc.
dard will often reduce the need for more extensive sampling requirements.
3. The modern approach, based on Japanese quality engineering [15], is
the pursuit of “zero defects” by applying tighter control over process
variability (meeting a so-called 6 sigma standard). Most pharmaceutical
products and their manufacturing processes in the United States
today, with the exception of sterile processes are designed to meet a
4 sigma limit (which would permit as many as eight defects per 1000
units). The new approach is to center the process (in which the grand
average is roughly equal to 100% of label potency or the target value
of a given specification) and to reduce the process variability or noise
around the mean or to achieve minimum variability by holding both
to the new standard, batch after batch. In so doing, a 6 sigma limit
may be possible (which is equivalent to not more than three to four
defects per 1 million units), also called “zero defects.” The goal of 6
sigma, “zero defects” is easier to achieve for liquid than for solid
pharmaceutical dosage forms [16].
Process characterization represents the methods used to determine the
critical unit operations or processing steps and their process variables, that usually
affect the quality and consistency of the product outcomes or product attributes.
Process ranging represents studies that are used to identify critical process
or test parameters and their respective control limits, which normally affect the
quality and consistency of the product outcomes of their attributes. The following
process characterization techniques may be used to designate critical unit
operations in a given manufacturing process.
A. Constraint Analysis
One procedure that makes subsystem evaluations and performance qualification
trials manageable is the application of constraint analysis. Boundary limits of
any technology and restrictions as to what constitutes acceptable output from
unit operations or process steps should in most situations constrain the number
of process variables and product attributes that require analysis. The application
of the constraint analysis principle should also limit and restrict the operational
range of each process variable and/or specification limit of each product attribute.
Information about constraining process variables usually comes from the
following sources:
• Previous successful experience with related products/processes
• Technical and engineering support functions and outside suppliers
• Published literatures concerning the specific technology under investigation
Copyright © 2003 Marcel Dekker, Inc.
A practical guide to constraint analysis comes to us from the application
of the Pareto Principle (named after an Italian sociologist) and is also known
as the 80–20 rule, which simply states that about 80% of the process output is
governed by about 20% of the input variables and that our primary job is to
find those key variables that drive the process.
The FDA in their proposed amendments to the CGMPs [17] have designated
that the following unit operations are considered critical and therefore
their processing variables must be controlled and not disregarded:
• Cleaning
• Weighing/measuring
• Mixing/blending
• Compression/encapsulation
• Filling/packaging/labeling
B. Fractional Factorial Design
An experimental design is a series of statistically sufficient qualification trials
that are planned in a specific arrangement and include all processing variables
that can possibly affect the expected outcome of the process under investigation.
In the case of a full factorial design, n equals the number of factors or process
variables, each at two levels, i.e., the upper (+) and lower (?) control limits.
Such a design is known as a 2n factorial. Using a large number of process
variables (say, 9) we could, for example, have to run 29, or 512, qualification
trials in order to complete the full factorial design.
The fractional factorial is designed to reduce the number of qualification
trials to a more reasonable number, say, 10, while holding the number of randomly
assigned processing variables to a reasonable number as well, say, 9. The
technique was developed as a nonparametric test for process evaluation by Box
and Hunter [18] and reviewed by Hendrix [19]. Ten is a reasonable number of
trials in terms of resource and time commitments and should be considered an
upper limit in a practical testing program. This particular design as presented in
Table 7 does not include interaction effects.
XI. OPTIMIZATION TECHNIQUES
Optimization techniques are used to find either the best possible quantitative
formula for a product or the best possible set of experimental conditions (input
values) needed to run the process. Optimization techniques may be employed in
the laboratory stage to develop the most stable, least sensitive formula, or in the
qualification and validation stages of scale-up in order to develop the most sta-
Copyright © 2003 Marcel Dekker, Inc.
Table 7 Fractional Factorial Design (9 Variables in 10 Experiments)
Trial no. X1 X2 X3 X4 X5 X6 X7 X8 X9
1 ? ? ? ? ? ? ? ? ?
2 + ? ? ? ? ? ? ? ?
3 ? ? ? + ? ? ? ? +
4 + ? + ? ? ? + ? ?
5 ? + ? + ? + ? + ?
6 + ? + ? + ? + ? +
7 ? + ? + + + ? + +
8 + + + ? + + + + ?
9 ? + + + + + + + +
10 + + + + + + + + +
Worst-case conditions: Trial 1 (lower control limit). Trial 10 (upper control limit). X variables
randomly assigned. Best values to use are RSD of data set for each trial. When adding up the data
by columns, + and ? are now numerical values and the sum is divided by 5 (number of +s or ?s).
If the variable is not significant, the sum will approach zero.
ble, least variable, robust process within its proven acceptable range(s) of operation,
Chapman’s so-called proven acceptable range (PAR) principle [20].
Optimization techniques may be classified as parametric statistical methods
and nonparametric search methods. Parametric statistical methods, usually
employed for optimization, are full factorial designs, half factorial designs, simplex
designs, and Lagrangian multiple regression analysis [21]. Parametric
methods are best suited for formula optimization in the early stages of product
development. Constraint analysis, described previously, is used to simplify the
testing protocol and the analysis of experimental results.
The steps involved in the parametric optimization procedure for pharmaceutical
systems have been fully described by Schwartz [22]. Optimization techniques
consist of the following essential operations:
1. Selection of a suitable experimental design
2. Selection of variables (independent Xs and dependent Ys) to be tested
3. Performance of a set of statistically designed experiments (e.g., 23 or
32 factorials)
4. Measurement of responses (dependent variables)
5. Development of a predictor, polynomial equation based on statistical
and regression analysis of the generated experimental data
6. Development of a set of optimized requirements for the formula based
on mathematical and graphical analysis of the data generated
Copyright © 2003 Marcel Dekker, Inc.
XII. WHAT ARE THE PROCESS VALIDATION OPTIONS?
The guidelines on general principles of process validation [1] mention three
options: (1) prospective process validation (also called premarket validation),
(2) retrospective process validation, and (3) revalidation. In actuality there are
four possible options.
A. Prospective Process Validation
In prospective process validation, an experimental plan called the validation
protocol is executed (following completion of the qualification trials) before the
process is put into commercial use. Most validation efforts require some degree
of prospective experimentation to generate validation support data. This particular
type of process validation is normally carried out in connection with the
introduction of new drug products and their manufacturing processes. The formalized
process validation program should never be undertaken unless and until
the following operations and procedures have been completed satisfactorily:
1. The facilities and equipment in which the process validation is to
be conducted meet CGMP requirements (completion of installation
qualification)
2. The operators and supervising personnel who will be “running” the
validation batch(es) have an understanding of the process and its requirements
3. The design, selection, and optimization of the formula have been
completed
4. The qualification trials using (10 ? size) pilot-laboratory batches have
been completed, in which the critical processing steps and process
variables have been identified, and the provisional operational control
limits for each critical test parameter have been provided
5. Detailed technical information on the product and the manufacturing
process have been provided, including documented evidence of product
stability
6. Finally, at least one qualification trial of a pilot-production (100 ? size)
batch has been made and shows, upon scale-up, that there were no
significant deviations from the expected performance of the process
The steps and sequence of events required to carry out a process validation
assignment are outlined in Table 8. The objective of prospective validation is to
prove or demonstrate that the process will work in accordance with a validation
master plan or protocol prepared for pilot-product (100 ? size) trials.
In practice, usually two or three pilot-production (100 ? ) batches are prepared
for validation purposes. The first batch to be included in the sequence
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Table 8 Master Plan or Outline of a Process Validation Program
Objective Proving or demonstrating that the process works
Type of validation Prospective, concurrent, retrospective, revalidation
Type of process Chemical, pharmaceutical, automation, cleaning
Definition of process Flow diagram, equipment/components, in-process, finished
product
Definition of process output Potency, yield, physical parameters
Definition of test methods Method, instrumentation, calibration, traceability, precision,
accuracy
Analysis of process Critical modules and variables defined by process capability
design and testing program
Control limits of critical vari- Defined by process capability design and testing proables
gram
Preparation of validation pro- Facilities, equipment, process, number of validation tritocol
als, sampling frequency, size, type, tests to perform,
methods used, criteria for success
Organizing for validation Responsibility and authority
Planning validation trials Timetable and PERT charting, material availability,
and disposal
Validation trials Supervision, administration, documentation
Validation finding Data summary, analysis, and conclusions
Final report and recommenda- Process validated, further trials, more process design,
tions and testing
may be the already successfully concluded first pilot batch at 100 ? size, which
is usually prepared under the direction of the organizational function directly
responsible for pilot scale-up activities. Later, replicate batch manufacture may
be performed by the pharmaceutical production function.
The strategy selected for process validation should be simple and straightforward.
The following factors are presented for the reader’s consideration:
1. The use of different lots of components should be included, i.e., APIs
and major excipients.
2. Batches should be run in succession and on different days and shifts
(the latter condition, if appropriate).
3. Batches should be manufactured in equipment and facilities designated
for eventual commercial production.
4. Critical process variables should be set within their operating ranges
and should not exceed their upper and lower control limits during
process operation. Output responses should be well within finished
product specifications.
Copyright © 2003 Marcel Dekker, Inc.
5. Failure to meet the requirements of the validation protocol with respect
to process inputs and output control should be subjected to requalification
following a thorough analysis of process data and formal
review by the CMC Coordination Committee.
B. Retrospective Validation
The retrospective validation option is chosen for established products whose
manufacturing processes are considered stable and when on the basis of economic
considerations alone and resource limitations, prospective validation programs
cannot be justified. Prior to undertaking retrospective validation, wherein
the numerical in-process and/or end-product test data of historic production
batches are subjected to statistical analysis, the equipment, facilities and subsystems
used in connection with the manufacturing process must be qualified in
conformance with CGMP requirements. The basis for retrospective validation
is stated in 21CFR 211.110(b): “Valid in-process specifications for such characteristics
shall be consistent with drug product final specifications and shall be
derived from previous acceptable process average and process variability estimates
where possible and determined by the application of suitable statistical
procedures where appropriate.”
The concept of using accumulated final product as well as in-process numerical
test data and batch records to provide documented evidence of product/
process validation was originally advanced by Meyers [26] and Simms [27] of
Eli Lilly and Company in 1980. The concept is also recognized in the FDA’s
Guidelines on General Principles of Process Validation [1].
Using either data-based computer systems [28,29] or manual methods,
retrospective validation may be conducted in the following manner:
1. Gather the numerical data from the completed batch record and include
assay values, end-product test results, and in-process data.
2. Organize these data in a chronological sequence according to batch
manufacturing data, using a spreadsheet format.
3. Include data from at least the last 20–30 manufactured batches for
analysis. If the number of batches is less than 20, then include all
manufactured batches and commit to obtain the required number for
analysis.
4. Trim the data by eliminating test results from noncritical processing
steps and delete all gratuitous numerical information.
5. Subject the resultant data to statistical analysis and evaluation.
6. Draw conclusions as to the state of control of the manufacturing process
based on the analysis of retrospective validation data.
7. Issue a report of your findings (documented evidence).
Copyright © 2003 Marcel Dekker, Inc.
One or more of the following output values (measured responses), which
have been shown to be critical in terms of the specific manufacturing process
being evaluated, are usually selected for statistical analysis.
1. Solid Dosage Forms
1. Individual assay results from content uniformity testing
2. Individual tablet hardness values
3. Individual tablet thickness values
4. Tablet or capsule weight variation
5. Individual tablet or capsule dissolution time (usually at t50%) or disintegration
time
6. Individual tablet or capsule moisture content
2. Semisolid and Liquid Dosage Forms
1. pH value (aqueous system)
2. Viscosity
3. Density
4. Color or clarity values
5. Average particle size or distribution
6. Unit weight variation and/or potency values
The statistical methods that may be employed to analyze numerical output
data from the manufacturing process are listed as follows:
1 Basic statistics (mean, standard deviation, and tolerance limits) [21]
2. Analysis of variance (ANOVA and related techniques) [21]
3. Regression analysis [22]
4. Cumulative sum analysis (CUSUM) [23]
5. Cumulative difference analysis [23]
6. Control charting (averages and range) [24,25]
Control charting, with the exception of basic statistical analysis, is probably
the most useful statistical technique to analyze retrospective and concurrent
process data. Control charting forms the basis of modern statistical process control.
C. Concurrent Validation
In-process monitoring of critical processing steps and end-product testing of
current production can provide documented evidence to show that the manufacturing
process is in a state of control. Such validation documentation can be
provided from the test parameter and data sources disclosed in the section on
retrospective validation.
Copyright © 2003 Marcel Dekker, Inc.
Test parameter Data source
Average unit potency End-product testing
Content uniformity End-product testing
Dissolution time End-product testing
Weight variation End-product testing
Powder-blend uniformity In-process testing
Moisture content In-process testing
Particle or granule size distribution In-process testing
Weight variation In-process testing
Tablet hardness In-process testing
pH value In-process testing
Color or clarity In-process testing
Viscosity or density In-process testing
Not all of the in-process tests enumerated above are required to demonstrate
that the process is in a state of control. Selections of test parameters
should be made on the basis of the critical processing variables to be evaluated.
D. Revalidation
Conditions requiring revalidation study and documentation are listed as follows:
1. Change in a critical component (usually refers to raw materials)
2. Change or replacement in a critical piece of modular (capital) equipment
3. Change in a facility and/or plant (usually location or site)
4. Significant (usually order of magnitude) increase or decrease in batch
size
5. Sequential batches that fail to meet product and process specifications
In some situations performance requalification studies may be required
prior to undertaking specific revalidation assignments.
The FDA process validation guidelines [1] refer to a quality assurance
system in place that requires revalidation whenever there are changes in packaging
(assumed to be the primary container-closure system), formulation, equipment
or processes (meaning not clear) which could impact on product effectiveness
or product characteristics and whenever there are changes in product
characteristics.
Approved packaging is normally selected after completing package performance
qualification testing as well as product compatibility and stability studies.
Since in most cases (exceptions: transdermal delivery systems, diagnostic tests,
and medical devices) packaging is not intimately involved in the manufacturing
process of the product itself, it differs from other factors, such as raw materials.
Copyright © 2003 Marcel Dekker, Inc.
The reader should realize that there is no one way to establish proof or
evidence of process validation (i.e., a product and process in control). If the
manufacturer is certain that its products and processes are under statistical control
and in compliance with CGMP regulations, it should be a relatively simple
matter to establish documented evidence of process validation through the use
of prospective, concurrent, or retrospective pilot and/or product quality information
and data. The choice of procedures and methods to be used to establish
validation documentation is left with the manufacturer.
This introduction was written to aid scientists and technicians in the pharmaceutical
and allied industries in the selection of procedures and approaches
that may be employed to achieve a successful outcome with respect to product
performance and process validation. The authors of the following chapters explore
the same topics from their own perspectives and experience. It is hoped
that the reader will gain much from the diversity and richness of these varied
approaches.
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45086, September 1978.
3. Good Manufacturing Practices for Pharmaceuticals, Willig, S. H. and Stoker, J.
R., Marcel Dekker, New York (1997).
4. Commentary, Pre-approval Inspections/Investigations, FDA, J. Parent. Sci. & Tech.
45:56–63 (1991).
5. Mead, W. J., Process validation in cosmetic manufacture, Drug Cosmet. Ind., (September
1981).
6. Chapman, K. G., A history of validation in the United States, Part I, Pharm. Tech.,
(November 1991).
7. Nash, R. A., The essentials of pharmaceutical validation in Pharmaceutical Dosage
Forms: Tablets, Vol. 3, 2nd ed., Lieberman, H. A., Lachman, L. and Schwartz, J.
B., eds., Marcel Dekker, New York (1990).
8. Nash, R. A., Product formulation, CHEMTECH, (April 1976).
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Dekker, New York (1993).
10. Nash, R. A., Making the Paper Match the Work, Pharmaceutical Formulation &
Quality (Oct/Nov 2000).
11. Guidance for Industry, Scale-Up & Postapproval Changes, CDER, FDA (Nov
1995).
12. Bala, G., An integrated approach to process validation, Pharm. Eng. 14(3) (1994).
13. Farkas, D. F., Unit operations optimization operations, CHEMTECH, July 1977.
Copyright © 2003 Marcel Dekker, Inc.
14. Nash, R. A., Streamlining Process Validation, Amer. Pharm. Outsourcing May
2001.
15. Ishikawa, K., What is Total Quality Control? The Japanese Way, Prentice-Hall,
Englewood Cliffs, NJ (1985).
16. Nash, R. A., Practicality of Achieving Six Sigma or Zero-Defects in Pharmaceutical
Systems, Pharmaceutical Formulation & Quality, Oct./Nov. 2001.
17. CGMP: Amendment of Certain Requirements, FDA Federal Register, May 3,
1996.
18. Box, G. E. and Hunter, J. S., Statistics for Experimenters, John Wiley, N.Y. (1978).
19. Hendrix, C. D., What every technologist should know about experimental design,
CHEMTECH (March 1979).
20. Chapman, K. G., The PAR approach to process validation, Pharm. Tech., Dec.
1984.
21. Bolton, S., Pharmaceutical Statistics: Practical and Clinical Applications, 3rd ed.,
Marcel Dekker, New York (1997).
22. Schwartz, J. B., Optimization techniques in product formulation. J. Soc. Cosmet.
Chem. 32:287–301 (1981).
23. Butler, J. J., Statistical quality control, Chem. Eng. (Aug. 1983).
24. Deming, S. N., Quality by Design, CHEMTECH, (Sept. 1988).
25. Contino, AV., Improved plant performance with statistical process control, Chem.
Eng. (July 1987).
26. Meyer, R. J., Validation of Products and Processes, PMA Seminar on Validation
of Solid Dosage Form Processes, Atlanta, GA, May 1980.
27. Simms, L., Validation of Existing Products by Statistical Evaluation, Atlanta, GA,
May 1980.
28. Agalloco, J. P., Practical considerations in retrospective validation, Pharm. Tech.
(June 1983).
29. Kahan, J. S., Validating computer systems, MD&DI (March 1987).
Copyright © 2003 Marcel Dekker, Inc.
1
Regulatory Basis for
Process Validation
John M. Dietrick
U.S. Food and Drug Administration, Rockville, Maryland, U.S.A.
Bernard T. Loftus
U.S. Food and Drug Administration, Washington, D.C., U.S.A.
I. INTRODUCTION
Bernard T. Loftus was director of drug manufacturing in the Food and Drug
Administration (FDA) in the 1970s, when the concept of process validation was
first applied to the pharmaceutical industry and became an important part of
current good manufacturing practices (CGMPs). His comments on the development
and implementation of these regulations and policies as presented in the
first and second editions of this volume are summarized below [1].
II. WHAT IS PROCESS VALIDATION?
The term process validation is not defined in the Food, Drug, and Cosmetic Act
(FD&C) Act or in FDA’s CGMP regulations. Many definitions have been offered
that in general express the same idea—that a process will do what it
purports to do, or that the process works and the proof is documented. A June
1978 FDA compliance program on drug process inspections [2] contained the
following definition:
This chapter was written by John M. Dietrick in his private capacity. No official support or endorsement
by the Food and Drug Administration is intended or should be inferred.
Copyright © 2003 Marcel Dekker, Inc.
A validated manufacturing process is one which has been proved to do what
it purports or is represented to do. The proof of validation is obtained
through the collection and evaluation of data, preferably, beginning from
the process development phase and continuing through the production
phase. Validation necessarily includes process qualification (the qualification
of materials, equipment, systems, buildings, personnel), but it also includes
the control on the entire process for repeated batches or runs.
The first drafts of the May 1987 Guideline on General Principles of Process
Validation [3] contained a similar definition, which has frequently been used in
FDA speeches since 1978, and is still used today: “A documented program which
provides a high degree of assurance that a specific process will consistently produce
a product meeting its pre-determined specifications and quality attributes.”
III. THE REGULATORY BASIS FOR
PROCESS VALIDATION
Once the concept of being able to predict process performance to meet user
requirements evolved, FDA regulatory officials established that there was a legal
basis for requiring process validation. The ultimate legal authority is Section
501(a)(2)(B) of the FD&C Act [4], which states that a drug is deemed to be
adulterated if the methods used in, or the facilities or controls used for, its
manufacture, processing, packing, or holding do not conform to or were not
operated or administrated in conformity with CGMP. Assurance must be given
that the drug would meet the requirements of the act as to safety and would
have the identity and strength and meet the quality and purity characteristics
that it purported or was represented to possess. That section of the act sets the
premise for process validation requirements for both finished pharmaceuticals
and active pharmaceutical ingredients, because active pharmaceutical ingredients
are also deemed to be drugs under the act.
The CGMP regulations for finished pharmaceuticals, 21 CFR 210 and
211, were promulgated to enforce the requirements of the act. Although these
regulations do not include a definition for process validation, the requirement is
implicit in the language of 21 CFR 211.100 [5], which states: “There shall be
written procedures for production and process control designed to assure that
the drug products have the identity, strength, quality, and purity they purport or
are represented to possess.”
IV. THE REGULATORY HISTORY OF
PROCESS VALIDATION
Although the emphasis on validation began in the late 1970s, the requirement
has been around since at least the 1963 CGMP regulations for finished pharmaceuticals.
The Kefauver-Harris Amendments to the FD&C Act were approved
Copyright © 2003 Marcel Dekker, Inc.
in 1962 with Section 501(a)(2)(B) as an amendment. Prior to then, CGMP and
process validation were not required by law. The FDA had the burden of proving
that a drug was adulterated by collecting and analyzing samples. This was
a significant regulatory burden and restricted the value of factory inspections of
pharmaceutical manufacturers. It took injuries and deaths, mostly involving
cross-contamination problems, to convince Congress and the FDA that a revision
of the law was needed. The result was the Kefauver–Harris drug amendments,
which provided the additional powerful regulatory tool that FDA required
to deem a drug product adulterated if the manufacturing process was not
acceptable. The first CGMP regulations, based largely on the Pharmaceutical
Manufacturers Association’s manufacturing control guidelines, were then published
and became effective in 1963. This change allowed FDA to expect a
preventative approach rather than a reactive approach to quality control. Section
505(d)(3) is also important in the implementation of process validation requirements
because it gives the agency the authority to withhold approval of a new
drug application if the “methods used in, and the facilities and controls used
for, the manufacture, processing, and packing of such drug are inadequate to
preserve its identity, strength, quality, and purity.”
Another requirement of the same amendments was the requirement that
FDA must inspect every drug manufacturing establishment at least once every
2 years [6]. At first, FDA did this with great diligence, but after the worst
CGMP manufacturing situations had been dealt with and violations of the law
became less obvious, FDA eased up its pharmaceutical plant inspection activities
and turned its resources to more important problems.
The Drug Product Quality Assurance Program of the 1960s and 1970s
involved first conducting a massive sampling and testing program of finished
batches of particularly important drugs in terms of clinical significance and
dollar volume, then taking legal action against violative batches and inspecting
the manufacturers until they were proven to be in compliance. This approach
was not entirely satisfactory because samples are not necessarily representative
of all batches. Finished product testing for sterility, for example, does not assure
that the lot is sterile. Several incidents refocused FDA’s attention to process
inspections. The investigation of complaints of clinical failures of several products
(including digoxin, digitoxin, prednisolone, and prednisone) by FDA found
significant content uniformity problems that were the result of poorly controlled
manufacturing processes. Also, two large-volume parenteral manufacturers experienced
complaints despite quality control programs and negative sterility testing.
Although the cause of the microbiological contamination was never proven,
FDA inspections did find deficiencies in the manufacturing process and it became
evident that there was no real proof that the products were sterile.
What became evident in these cases was that FDA had not looked at the
process itself—certainly not the entire process—in its regulatory activities; it
was quality control- rather than quality assurance-oriented. The compliance offi-
Copyright © 2003 Marcel Dekker, Inc.
cials were not thinking in terms of process validation. One of the first entries
into process validation was a 1974 paper presented by Ted Byers, entitled “Design
for Quality” [7]. The term validation was not used, but the paper described
an increased attention to adequacy of processes for the production of pharmaceuticals.
Another paper—by Bernard Loftus before the Parenteral Drug Association
in 1978 entitled “Validation and Stability” [8]—discussed the legal basis
for the requirement that processes be validated.
The May 1987 Guideline on General Principles of Process Validation [3]
was written for the pharmaceutical, device, and veterinary medicine industries.
It has been effective in standardizing the approach by the different parts of the
agency and in communicating that approach to manufacturers in each industry.
V. UPDATE
As discussed in the preceding sections, process validation has been a legal requirement
since at least 1963. Implementation of the requirement was a slow
and deliberate process, beginning with the development and dissemination of an
agency policy by Loftus, Byers, and others, and leading to the May 1987 guideline.
The guideline quickly became an important source of information to pharmaceutical
manufacturers interested in establishing a process validation program.
Many industry organizations and officials promoted the requirements as
well as the benefits of validation. Many publications, such as Pharmaceutical
Process Validation [1] and various pharmaceutical industry journal articles,
cited and often expanded on the principals in the guideline. During the same
period, computer validation—or validation of computer controlled processes—
also became a widely discussed topic in both seminars and industry publications.
The regulatory implementation of the validation requirement was also a
deliberate process by FDA. During the 1980s, FDA investigators often reported
processes that had not been validated or had been inadequately validated. Batch
failures were often associated with unvalidated manufacturing processes. The
FDA issued a number of regulatory letters to deficient manufacturers citing the
lack of adequate process validation as a deviation from CGMP regulations
(21CFR 211.100), which causes the drug product to be adulterated within the
meaning of Section 501(a)(2)(B) of the federal FD&C Act. Process validation
was seldom the only deficiency listed in these regulatory letters. The failure of
some manufacturers to respond to these early warnings resulted in FDA filing
several injunction cases that included this charge in the early 1990s. Most of
these cases resulted in consent decrees, and ultimately the adoption of satisfactory
process validation programs by the subject manufacturers. One injunction
case filed in 1992, however, was contested in court and led to a lengthy written
order and opinion by the U.S. District Court in February of 1993 [9]. The court
Copyright © 2003 Marcel Dekker, Inc.
affirmed the requirement for process validation in the current good manufacturing
regulations, and ordered the defendants to perform process validation studies
on certain drug products, as well as equipment cleaning validation studies. This
case and the court’s ruling were widely circulated in the pharmaceutical industry
and became the subject of numerous FDA and industry seminars.
The court also criticized the CGMP regulations for their lack of specificity,
along with their ambiguity and vagueness. Responding to this criticism,
FDA drafted revisions to several parts of these regulations. The proposed revisions
were published in the Federal Register on May 3, 1996 [10]. One of the
main proposed changes was intended to emphasize and clarify the process validation
requirements. The proposal included a definition of process validation
(the same definition used in the 1987 guideline), a specific requirement to validate
manufacturing processes, and minimum requirements for performing and
documenting a validation study. These were all implied but not specific in the
1978 regulation. In proposing these changes, FDA stated that it was codifying
current expectations and current industry practice and did not intend to add new
validation requirements. Comments from all interested parties were requested
under the agency’s rule-making policies, and approximately 1500 comments
were received. Most of the responses to the changes regarding process validation
supported the agency’s proposals, but there were many comments regarding the
definitions and terminology proposed about which processes and steps in a process
should or should not require validation, the number of batches required for
process validation, maintenance of validation records, and the assignment of
responsibility for final approval of a validation study and change control decisions.
Because of other high-priority obligations, the agency has not yet completed
the evaluation of these responses and has not been able to publish the
final rule. In addition to the official comments, the proposed changes prompted
numerous industry and FDA seminars on the subject.
Process validation is not just an FDA or a U.S. requirement. Similar requirements
are included in the World Health Organization (WHO), the Pharmaceutical
Inspection Co-operation Scheme (PIC/S), and the European Union (EU)
requirements, along with those of Australia, Canada, Japan, and other international
authorities.
Most pharmaceutical manufacturers now put substantial resources into
process validation for both regulatory and economic reasons, but despite continued
educational efforts by both the agency and the pharmaceutical industry,
FDA inspections (both domestically and internationally) continue to find some
firms manufacturing drug products using unvalidated or inadequately validated
processes. Evidently there is still room for improvement, and continued discussion,
education, and occasional regulatory action appears warranted.
The future of process validation is also of great interest, especially with
the worldwide expansion of pharmaceutical manufacturing and the desire for
Copyright © 2003 Marcel Dekker, Inc.
harmonized international standards and requirements. Many manufacturers are
also working on strategies to reduce the cost of process validation and incorporate
validation consideration during product design and development. New technologies
under development for 100% analysis of drug products and other innovations
in the pharmaceutical industry may also have a significant effect on
process validation concepts and how they can be implemented and regulated.
REFERENCES
1. Loftus, B. T., Nash, R. A., ed. Pharmaceutical Process Validation. vol. 57. New
York: Marcel Dekker (1993).
2. U.S. Food and Drug Administration. Compliance Program no. 7356.002.
3. U.S. Food and Drug Administration. Guideline on General Principles of Process
Validation. Rockville, MD: FDA, 1987.
4. Federal Food Drug and Cosmetic Act, Title 21 U.S. Code, Section 501 (a)(2)(B).
5. Code of Federal Regulations, Title 21, Parts 210 & 211. Fed Reg 43, 1978.
6. U.S. Code, Federal Food Drug and Cosmetic Act, Title 21, Section 510 (h).
7. Byers, T. E. Design for quality, Manufacturing Controls Seminar, Proprietary Association,
Cherry Hill, NJ, Oct. 11, 1974.
8. Loftus, B. T. Validation and stability, meeting of Parenteral Drug Association,
1978.
9. U.S. v. Barr Laboratories, Inc., et al., Civil Action No. 92-1744, U.S. District Court
for the District of New Jersey, 1973.
10. Code of Federal Regulations, Title 21, Parts 21 & 211, Proposed Revisions, Fed
Reg (May 3, 1996).
Copyright © 2003 Marcel Dekker, Inc.
2
Prospective Process Validation
Allen Y. Chao
Watson Labs, Carona, California, U.S.A.
F. St. John Forbes
Wyeth Labs, Pearl River, New York, U.S.A.
Reginald F. Johnson and Paul Von Doehren
Searle & Co., Inc., Skokie, Illinois, U.S.A.
I. INTRODUCTION
Validation is an essential procedure that demonstrates that a manufacturing process
operating under defined standard conditions is capable of consistently producing
a product that meets the established product specifications. In its
proposed guidelines, the U.S. Food and Drug Administration (FDA) has offered
the following definition for process validation [1].
Process validation is establishing documented evidence that provides a
high degree of assurance that a specific process (such as the manufacture of
pharmaceutical dosage forms) will consistently produce a product meeting its
predetermined specifications and quality characteristics.
Many individuals tend to think of validation as a stand-alone item or an
afterthought at the end of the entire product/process development sequence.
Some believe that the process can be considered validated if the first two or
three batches of product satisfy specifications.
Prospective validation is a requirement (Part 211), and therefore it makes
validation an integral part of a carefully planned, logical product/process developmental
program. An outline of the development sequence and requirements
relevant to process validation is presented in Figure 1. After briefly discussing
organizational aspects and documentation, the integration of validation into the
product development sequence is discussed. At the end of the chapter there is a
Copyright © 2003 Marcel Dekker, Inc.
brief discussion of specific ways in which experimental programs can be defined
to ensure that critical process development and validation objectives are met.
II. ORGANIZATION
Prospective validation requires a planned program and organization to carry it
to successful completion. The organization must have clearly defined areas of
responsibility and authority for each of the groups involved in the program so
that the objective of validating the process can be met. The structure must be
tailored to meet the requirements in the specific organization, and these will
vary from company to company. The important point is that a defined structure
exists, is accepted, and is in operation. An effective project management structure
will have to be established in order to plan, execute, and control the program.
Without clearly defined responsibilities and authority, the outcome of
process validation efforts may not be adequate and may not comply with CGMP
requirements.
III. MASTER DOCUMENTATION
An effective prospective validation program must be supported by documentation
extending from product initiation to full-scale production. The complete
documentation package can be referred to as the master documentation file.
It will accumulate as a product concept progresses to the point of being
placed in full-scale production, providing as complete a product history as possible.
The final package will be the work of many individual groups within the
organization. It will consist of reports, procedures, protocols, specifications, analytical
methods, and any other critical documents pertaining to the formulation,
process, and analytical method development. The package may contain the actual
reports, or it may utilize cross-references to formal documentation, both
internal and external to the organization.
The ideal documentation package will contain a complete history of the
final product that is being manufactured. In retrospect, it would be possible to
trace the justification or rationale behind all aspects of the final product, process,
and testing.
The complete master documentation file not only provides appropriate
rationale for the product, process, and testing, but also becomes the reference
source for all questions relating to the manufacture of a product at any plant
location. This master documentation file, however, should not be confused with
the concept of the master product document, which is essential for routine manufacturing
of the product and is described later in the chapter. The master docu-
Copyright © 2003 Marcel Dekker, Inc.
Figure 1 Prospective process validation.
Copyright © 2003 Marcel Dekker, Inc.
mentation file should contain all information that was generated during the entire
product development sequence to a validation process.
IV. PRODUCT DEVELOPMENT
Product development usually begins when an active chemical entity has been
shown to possess the necessary attributes for a commercial product. The product
development activities for the active chemical entity, formulation, and process
form the foundation upon which the subsequent validation data are built.
Generally, product development activities can be subdivided into formulation
and process development, along with scale-up development.
A. Formulation Development
Formulation development provides the basic information on the active chemical,
the formula, and the impact of raw materials or excipients on the product. Typical
supportive data generated during these activities may include the following:
1. Preformulation profile or characterization of the components of the
formula, which includes all the basic physical or chemical information
about the active pharmaceutical ingredients (API, or the chemical entity)
and excipients
2. Formulation profile, which consists of physical and chemical characteristics
required for the products, drug-excipient compatibility studies,
and the effect of formulation on in vitro dissolution
3. Effect of formulation variables on the bioavailability of the product
4. Specific test methods
5. Key product attributes and/or specifications
6. Optimum formulation
7. Development of cleaning procedures and test methods
Formulation development should not be considered complete until all those factors
that could significantly alter the formulation have been studied. Subsequent
minor changes to the formulation, however, may be acceptable, provided they
are thoroughly tested and are shown to have no adverse effect on product.
B. Process Development
Even though the process development activities typically begin after the formulation
has been developed, they may also occur simultaneously. The majority of
the process development activities occur either in the pilot plant or in the pro-
Copyright © 2003 Marcel Dekker, Inc.
posed manufacturing plant. The process development program should meet the
following objectives:
1. Develop a suitable process to produce a product that meets all
a. Product specifications
b. Economic constraints
c. Current good manufacturing practices (CGMPs)
2. Identify the key process parameters that affect the product attributes
3. Identify in-process specifications and test methods
4. Identify generic and/or specific equipment that may be required
It is important to remember that cleaning procedures should at least be in the
final stages of development, as equipment and facilities in the pilot or proposed
manufacturing plant are involved, and the development of the cleaning verification
test methods must be complete.
Process development can be divided into several stages.
Design
Challenging of critical process parameters
Verification of the developed process
Typical activities in these areas are illustrated in Figure 2.
1. Design
This is the initial planning stage of process development. The design of the
process should start during or at the end of the formulation development to
define the process to a large extent. One aspect of the process development
to remember is end user (manufacturing site) capabilities. In other words, the
practicality and the reality of the manufacturing operation should be kept in
perspective. Process must be developed in such a manner that it can easily be
transferred to the manufacturing site with minimal issues. During this stage,
technical operations in both the manufacturing and quality control departments
should be consulted.
Key documents for the technical definition of the process are the flow
diagram, the cause-and-effect diagram, and the influence matrix. The details of
the cause-and-effect diagram and the influence matrix will be discussed under
experimental approach in a later section.
The flow diagram identifies all the unit operations, the equipment used,
and the stages at which the various raw materials are added. The flow diagram
in Figure 3 outlines the sequence of process steps and specific equipment to be
used during development for a typical granulation solid dosage from product.
The flow diagram provides a convenient basis on which to develop a detailed
list of variables and responses.
Copyright © 2003 Marcel Dekker, Inc.
Figure 2 Product development flow.
Copyright © 2003 Marcel Dekker, Inc.
Figure 3 Typical process flow—granulated product.
Copyright © 2003 Marcel Dekker, Inc.
Preliminary working documents are critical, but they should never be cast
in stone, since new experimental data may drastically alter them. The final version
will eventually be an essential part of the process characterization and
technical transfer documents.
Regardless of the stage of formulation/process development being considered,
a detailed identification of variables and responses is necessary for early
program planning. Typical variables and responses that could be expected in a
granulated solid dosage form are listed in Table 1. This list is by no means
complete and is intended only as an example.
Table 1 Typical Variables and Responses: Granulated Product
Process step Control variables Measured responses
Preblending Blending time Blend uniformity
rpm
Load size
Order of addition
Granulating Load size Density
Amount of granulating agent Yield
Solvent addition rate
rpm
Granulation time
Drying Initial temperature Density
Load size Moisture content
Drying temperature program Yield
Air flow program
Drying time
Cooling time
Sizing Screen type Granule size distribution
Screen size Loose density
Feed rate Packed density
Blending Load size Blend uniformity
rpm Flow characteristics
Blending time Particle size distribution
Tableting Compression rate Weight variation
Granule feed rate Friability
Precompression force Hardness
Compression force Thickness
Disintegration time
Dissolution
Dosage form uniformity
Copyright © 2003 Marcel Dekker, Inc.
As the developmental program progresses, new discoveries will provide
an update of the variables and responses. It is important that current knowledge
be adequately summarized for the particular process being considered. It should
be pointed out, however, that common sense and experience must be used in
evaluating the variables during process design and development. An early transfer
of the preliminary documentation to the manufacturing and quality control
departments is essential, so that they can begin to prepare for any new equipment
or facilities that may be required.
2. Challenging of Process Parameters
Challenging of process parameters (also called process ranging) will test
whether or not all of the identified process parameters are critical to the product
and process being developed. These studies determine:
The feasibility of the designed process
The criticality of the parameters
This is usually a transition stage between the laboratory and the projected
final process. Figure 4 also shows typical responses that may have to be evaluated
during the ranging studies on the tableted product.
3. Challenging of Critical Process Parameters or
Characterization of the Process
Process characterization provides a systematic examination of critical variables
found during process ranging. The objectives of these studies are
Confirm critical process parameters and determine their effects on product
quality attributes.
Establish process conditions for each unit operation.
Determine in-process operating limits to guarantee acceptable finished
product and yield.
Confirm the validity of the test methods.
A carefully planned and coordinated experimental program is essential
in order to achieve each of these objectives. Techniques to assist in defining
experimental programs are mentioned later in the chapter.
The information summarized in the process characterization report provides
a basis for defining the full-scale process.
4. Verification
Verification is required before a process is scaled up and transferred to production.
The timing of this verification may be critical from a regulatory point of
view, as the there is little or no room for modifying the parameter values and
Copyright © 2003 Marcel Dekker, Inc.
specifications, particularly shifting or expanding after the regulatory submission
is made. This ensures that it behaves as designed under simulated production
conditions and determines its reproducibility. Key elements of the process verification
runs should be evaluated using a well-designed in-process sampling procedure.
These should be focused on potentially critical unit operations. Validated
in-process and final-product analytical procedures should always be used.
Sufficient replicate batches should be produced to determine between- and
within-batch variations.
Testing during these verification runs will be more frequent and cover
more variables than would be typical during routine production. Typically the
testing requirements at the verification stage should be the same or more than
the proposed testing for process validation runs. The typical process verification
analysis of tabulated product includes the following:
Unit operation Analysis
Preblending Potency (if required)
Granulation Potency (if required)
Sizing Particle size distribution
Loss on drying (LOD)
Blending Uniformity
Particle size distribution
Tableting Weight
Hardness
Thickness
Disintegration and/or dissolution
Friability
Potency
Dosage uniformity
Degradants
For maximum information, the process should not be altered during the verification
trials.
5. Development Documentation
The developmental documentation to support the validation of the process may
contain the following:
Process challenging and characterization reports that contain a full description
of the studies performed
Development batch record
Raw material test methods and specifications
Copyright © 2003 Marcel Dekker, Inc.
Equipment list and qualification and calibration status
Process flow diagram
Process variable tolerances
Operating instructions for equipment (where necessary)
In-process quality control program, including:
Sampling intervals
Test methods
Finished Product
Stability
Critical unit operation
Final product specifications
Safety evaluation
Chemical
Process
Special production facility requirements
Cleaning
Procedure for equipment and facilities
Test methods
Stability profile of the product
Produced during process development
Primary packaging specification
V. DEVELOPMENT OF MANUFACTURING CAPABILITY
There must be a suitable production facility for every manufacturing process
that is developed. This facility includes buildings, equipment, staff, and supporting
functions.
As development activities progress and the process becomes more clearly
defined, there must be a parallel assessment of the capability to manufacture the
product. The scope and timing of the development of manufacturing capability
will be dependent on the process and the need to utilize or modify existing
facilities or establish new ones.
VI. FULL-SCALE PRODUCT/PROCESS DEVELOPMENT
The development of the final full-scale production process proceeds through the
following steps:
Process scale-up studies
Qualification trials
Process validation runs
Copyright © 2003 Marcel Dekker, Inc.
A. Scale-Up Studies
The transition from a successful pilot-scale process or research scale to a fullscale
process requires careful planning and implementation. Although a large
amount of information has been gathered during the development of the process
(i.e., process characterization and process verification studies), it does not necessarily
follow that the full-scale process can be completely predicted.
Many scale-up parameters are nonlinear. In fact, scale-up factors can be
quite complex and difficult to predict, based only on experience with smallerscale
equipment. In general, the more complex the process, the more complex
the scale-up effect.
For some processes, the transition from pilot scale or research scale to full
scale is relatively easy and orderly. For others the transition is less predictable.
More often than not there will be no serious surprises, but this cannot be guaranteed.
Individuals conducting the transfer into production should be thoroughly
qualified on both small- and large-scale equipment.
The planning for scale-up should follow the same general outline followed
for process characterization and verification. It usually begins when process
development studies in the laboratory have successfully shown that a product
can be produced within specification limits for defined ranges of process parameters.
Frequently, because of economic constraints, a carefully selected excipient
may be used as a substitute for the expensive active chemical in conducting
initial scale-up studies. Eventually, the active chemical will have to be used to
complete the scale-up studies, however.
It is common sense that every effort will be made to conduct the final
scale-up studies under CGMP conditions, thus any product produced with specifications
can be considered for release as a finished salable product (for overthe-
counter products only).
B. Qualification Trials
Once the scale-up studies have been completed, it may be necessary to manufacture
one or more batches at full scale to confirm that the entire manufacturing
process, comprising several different unit operations, can be carried out
smoothly. This may occur prior to or after the regulatory submission, depending
on the strategy used in filing.
C. Process Validation Runs
After the qualification trials have been completed, the protocol for the full-scale
process validation runs can be written. Current industry standard for the validation
batches is to attempt to manufacture them at target values for both process
Copyright © 2003 Marcel Dekker, Inc.
parameters and specifications. The validation protocol is usually the joint effort
of the following groups:
Research and development
Pharmaceutical technology or technical services
Quality control (quality assurance)
Manufacturing
Engineering
One of these groups usually coordinates the activities.
A complete qualification protocol will contain specific sections; however,
there can be considerable variation in individual protocol. Section content typical
validation protocol may consist of the following:
Safety instructions
Environmental restrictions
Gas or liquid discharge limitations
Solid or scrap disposal instructions
Equipment
Description
Operation
Cleaning
Raw materials
Pertinent characteristics
Acceptance limits
Analytical methods
Packaging and storage
Handling precautions
Process flow chart
Critical parameters and related means of controls
Responsibilities of each of the groups participating
Cleaning validation/verification requirements
Master batch components (percentage by weight)
Production batch component (by weight)
Process batch record
Process sequence
Process instructions
Material usage
Product testing
In-process testing and acceptance criteria
Finished product testing and acceptance criteria
Test method references
Formulation
Copyright © 2003 Marcel Dekker, Inc.
Validation sampling and testing
In-process
Finished product
Definition of validation criteria
Lower and upper acceptance limits
Acceptable variation
Cleaning sampling plan (locations, type, and number of samples)
It is expected that acceptable, salable products will be produced, since all qualification
batches will be produced using a defined process under CGMP conditions
with production personnel.
A question that always arises is how many replicate batches or lots must
be produced for a validation protocol to be valid or correct. There is no absolute
answer. Obviously, a single batch will provide the minimum amount of data.
As the number of replicated batches increases, the information increases. The
FDA, however, has determined that the minimum number of validation batches
should be three.
D. Master Product Document
An extensive quantity of documents is generated at each stage of the development
and validation of the final production process. Some of these documents
will be directly related to the manufacture of the final products. Others may
provide the basis for decisions that ultimately result in the final process.
The documents that are required for manufacturing the product then become
the master product document. This document must be capable of providing
all of the information necessary to set up the process to produce a product
consistently and one that meets specifications in any location.
Items that will normally be included in the master product document are
Batch manufacturing record
Master formulation
Process flow diagram
Master manufacturing instructions
Master packaging instructions
Specifications
Sampling (location and frequency)
Test methods
Process validation data
Each of the above items must contain sufficient detailed information to permit
the complete master product document to become an independent, single package
that will provide all information necessary to set up and produce a product.
Copyright © 2003 Marcel Dekker, Inc.
VII. DEFINING EXPERIMENTAL PROGRAMS
The objective in this section is to examine experiments or combinations of related
experiments that make up development programs so that adequate justification
can be developed for the formulation, process, and specifications. The
emphasis will be on techniques to increase developmental program effectiveness.
A logical and systematic approach to each experimental situation is essential.
Any experiment that is performed without first defining a logical approach
is certain to waste resources. The right balance between overplanning and underplanning
should always be sought.
It is usually impossible to define a substantial experimental effort at the
beginning and then execute it in every detail without modification. To overcome
this, it is convenient to split the program into a number of stages.
Each stage will normally consist of several specific experiments. The earlier
experiments tend to supply initial data concerning the process and define
preliminary operating ranges for important variables. As results become available
from each stage, they can be used to assist in defining subsequent stages
in the experimental program. In some cases it may be necessary to redefine
completely the remainder of the experimental program on the basis of earlier
results.
The following discussion describes some techniques to help improve experimental
program effectiveness. A logical and systematic approach coupled
with effective communication among individuals associated with the program is
emphasized. Topics to be discussed include
Defining program scope
Process summary
Experimental design and analysis
Experiment documentation
Program organization
A. Program Scope
Defining a clear and detailed set of objectives is a necessary first step in any
experimental program. Some similarity exists between objectives for different
products and processes using similar existing technology. For products and processes
at the forefront of technology, the definition of specific experimental
objectives can be a continuing activity throughout product development.
Constraints on planning experimental programs can be classified according
to their impact on time, resources, and budget. The effect and impact of
these should be incorporated into the experimental program early to avoid compromising
critical program objectives.
Copyright © 2003 Marcel Dekker, Inc.
B. Process Summary
An initial clear understanding of the formulation and/or process is important.
The following techniques can assist in summarizing current process knowledge.
1. Flow Diagram
A process flow diagram (Fig. 3) can often provide a focal point of early program
planning activities. This diagram outlines the sequence of process steps and
specific equipment to be used during development for a typical granulated product.
Flow diagram complexity will depend on the particular product and process.
The flow diagram provides a convenient basis on which to develop a detailed
list of variables and responses.
2. Variables and Responses
For process using existing technology, many of the potential variables and responses
may have already been identified in previous product-development
studies or in the pharmaceutical literature. Once properly identified, the list of
variables and responses for the process is not likely to change appreciably. Typical
variables and responses that could be expected in a granulated solid dosage
form are listed in Table 1.
In addition, the relative importance of variables and responses already
identified will likely shift during development activities.
3. Cause-and-Effect Diagram
An efficient representation of complex relationships between many process and
formulation variables (causes), and a single response (effect) can be shown by
using a cause-and-effect diagram [1]. Figure 4 is a simple example.
A central arrow in Figure 4 points to a particular single effect. Branches
off the central arrow lead to boxes representing specific process steps. Next,
principle factors of each process step that can cause or influence the effect are
drawn as subbranches of each branch, until a complete cause-and-effect diagram
is developed. This should be as detailed a summary as possible. An example of
a more complex cause-and-effect diagram is illustrated in Figure 5. A separate
summary for each critical product characteristic (e.g., weight variation, dissolution,
friability) should be made.
4. Influence Matrix
Once the variables and responses have been identified, it is useful to summarize
their relationships in an influence matrix format, as shown in Figure 6. Based
on the available knowledge, each process variable is evaluated for its potential
Copyright © 2003 Marcel Dekker, Inc.
Figure 4 Simple cause-and-effect diagram.
Copyright © 2003 Marcel Dekker, Inc.
Figure 5 Cause-and-effect diagram (granulated product).
Copyright © 2003 Marcel Dekker, Inc.
Figure 6 Influence matrix for variables and responses (simplified).
Copyright © 2003 Marcel Dekker, Inc.
effects on each of the process responses or product characteristics. The strength
of the relationship between variables and responses can be indicated by some
appropriate notation, such as strong (S), moderate (M), weak (W), or none (N),
together with special classifications such as unknown (?).
Construction of the influence matrix assists in identifying those variables
with the greatest influence on key process or product characteristics. These variables
are potentially the most critical for maintaining process control and should
be included in the earliest experiments. Some may continue to be investigated
during development and scale-up.
VIII. EXPERIMENTAL DESIGN AND ANALYSIS
Many different experimental designs and analysis methods can be used in development
activities (Fig. 7). Indeed, the possibilities could fill several books. Fortunately,
in any given situation, it is not necessary to search for that single
design or analysis method that absolutely must be used; there are usually many
possibilities. In general, designs that are usable offer different levels of efficiency,
complexity, and effectiveness in achieving experimental objectives.
A. Types of Design
It is not possible to list specific designs that will always be appropriate for
general occasions. Any attempt to do so would be sure to be ineffective, and
the uniqueness of individual experimental situation carefully, including
Specific objectives
Available resources
Availability of previous theoretical results
Relevant variables and responses
Qualifications and experience of research team members
Cost of experimentation
It should also be determined which design is appropriate. A statistician who is
experienced in development applications can assist in suggesting and evaluating
candidate designs. In some cases, the statistician should be a full-time member
of the research team.
B. Data Analysis
The appropriate analysis of the experimental results will depend on the experimental
objectives, the design used, and the characteristics of the data collected
during the experiment. In many cases, a simple examination of a tabular or
Copyright © 2003 Marcel Dekker, Inc.
Figure 7 Experimental design example.
Copyright © 2003 Marcel Dekker, Inc.
graphical presentation of the data will be sufficient. In other cases, a formal
statistical analysis may be required in order to draw any conclusions at all. It
depends on the particular experimental situation. No rules of thumb are available.
In general, the simplest analysis consistent with experimental objectives
and conditions is the most appropriate.
C. Experiment Documentation
Documentation is essential to program planning and coordination, in addition to
the obvious use for the summary of activities and results. Written communication
becomes important for larger complex programs, especially when conducted
under severe constraints on time and resources. Documentation can consist
of some or all of the following items:
1. Objectives; an exact statement of quantifiable results expected from
the experiment
2. Experimental design; a detailed list of the experimental conditions to
be studied and the order of investigation
3. Proposed/alternate test methods
a. A list of test methods consistent with the type of experiment being
performed
b. A detailed description of the steps necessary to obtain a valid
measurement
c. Documentation supporting the accuracy, precision, sensitivity,
and so on of the test methods
4. Equipment procedures; documentation of safety precautions and stepby-
step methods for equipment setup, operation, and cleanup
5. Sampling plans; the type, number, location, and purpose of samples
to be taken during the experiment; in addition, the type and number
of all measurements to be performed on each sample
6. Protocol; a formal written experimental plan that presents the aforementioned
experimental documentation in a manner suitable for review
7. Data records
a. Experiment log; details of events in the experiment noting process
adjustments and any unusual occurrences
b. In-process measurements; records of the magnitude of critical
process parameters during the experimental sequence
Sample measurements; recorded values of particular measurements
on each sample
8. Report; documentation of experiment implementation, exceptions/
modifications to the protocol, results, and conclusion
Copyright © 2003 Marcel Dekker, Inc.
D. Program Organization
Throughout the experimental phases of the development program, it is essential
to maintain effective communication among various team members. This is facilitated
by having one individual with the necessary technical and managerial
skills assume responsibility for the experimental program, including procuring
resources and informing management of progress.
In a large experimental program, the responsible individual may serve as
a project leader or manager with little or no technical involvement.
IX. SUMMARY
Prospective validation of a production process utilizes information generated
during the entire development sequence that produced the final process.
Validation is supported by all phases of development from the product
concept.
As a potential product moves through the various developmental stages,
information is continually generated and incorporated into a master documentation
file. When the validation runs are planned for the final process, they will
be based on the master documentation file contents. The information generated
during the validation runs is usually the last major item to go into the master
documentation file.
An abstract of the master documentation file is the master product document,
which is the source of all information required to set up the process at
any location.
Though validation may seem to be a stand-alone item, it actually is an
integral portion of the entire product/process development sequence.
REFERENCES
1. FDA. Guidelines on General Principles of Process Validation. Rockville, MD: Division
of Manufacturing and Product Quality (HFN-320) Center for Drugs and Biologics
(May 1987).
2. Box, G. E. P., Gunter, W. G., and Hunter, J. S. Statistics for Experimenters: An
Introduction to Design, Data Analysis, and Model Building. New York: Wiley
(1978).
3. Box, G. E. P., and Draper, N. R. Evolutionary Operation: A Statistical Method for
Process Improvement. New York: Wiley (1969).
4. Cornell, J. A. Experiments with Mixtures: Design, Models and the Analysis of Mixture
Data. New York: Wiley (1981).
5. Daniel, C. Applications of Statistics to Industrial Experiments. New York: Wiley
(1976).
Copyright © 2003 Marcel Dekker, Inc.
6. Davies, O. L., ed. The Design and Analysis of Industrial Experiments. New York:
Longman Group (1978).
7. Diamond, W. J. Practical Experiment Designs for Engineers and Scientists. Belmont,
CA: Lifetime Learning Publications (1981).
8. Ott, E. R. Process Quality Control: Troubleshooting and Interpretation of Data.
New York: McGraw-Hill (1975).
9. Anderson, N. R., Banker, G. S., and Peck, G. E. Pharmaceutical Dosage Forms:
Tablets. vol. III. New York: Marcel Dekker (1981).
Copyright © 2003 Marcel Dekker, Inc.
3
Retrospective Validation
Chester J. Trubinski
Church & Dwight Co., Inc., Princeton, New Jersey, U.S.A.
I. INTRODUCTION
In the present-day pharmaceutical industry the Food and Drug Administration
(FDA) expects firms to have validated manufacturing processes. Process validation
has been defined as a documented program that provides a high degree of
assurance that a specific process will consistently produce a product meeting
predetermined specifications [1]. For new products or existing products that
have recently undergone reformulation, validation is usually an integral part of
the process development effort. No such opportunity exists for older established
products, however. Of the brands recognized as medical or scientific breakthroughs
of the 20th century that continue to be marketed, 21 were introduced
before 1980 [2]. This suggests product lines are likely to contain a product for
which the manufacturing processes have not been validated, at least not to the
extent that is now expected.
II. PROCESS VALIDATION STRATEGIES
The FDA has published a guideline for use by industry that outlines general
principles considered acceptable parts of process validation [1]. Pharmaceutical
firms have been inspected against this standard and those found wanting have
been cited or had approval to manufacture product denied. Indeed, statistics
compiled by the FDA for fiscal year 1997 show inadequate process validation
as one of the top 10 reasons for withholding approval [3]. One way for a firm
to satisfy the requirement for validated processes is to identify those products
that have been on the market for some time and use the wealth of production,
Copyright © 2003 Marcel Dekker, Inc.
testing, and control data to demonstrate that the process is reliable. This strategy
is commonly referred to as retrospective validation. Historical data also may
be used to augment an earlier validation in cases in which the product has
changed.
A. Product Selection Criteria for Retrospective Validation
For a product to be considered for retrospective validation, it must have a stable
process; that is, one in which the method of manufacture has remained essentially
unchanged for a period of time.
The first step in the product selection process is therefore to obtain a
summary of changes in the method of manufacture. In most companies such
information is part of the master batch record file. Then a time interval is selected
that represents the last 20 to 30 batches. Products for which there is no
record of a change in the method of manufacture or control during this period
can be regarded as candidates for validation. The 20-to-30-batch rule originates
from control chart principals, which consider 20 to 30 points that plot within
the limits as evidence of a stable process [4]. Once this criterion is met, the
number selected is actually somewhat arbitrary, as there is no one number that
is correct for every product. The ideal number of batches required to study a
product is theoretically the number that permits all process variables to come
into play. By process variables, we mean raw materials from different but approved
vendors, introduction of similar but different pieces of equipment, personnel
and seasonal changes, and the like. This academic approach may present
a rather unwieldy situation, especially for a high-volume product, for which
change in process variables occurs infrequently. The influence of seasonal
changes is such an example. In such instances, compromise will need to be
reached between process variables included for study and the number of batches
that can be examined for data. This decision making is best handled by a validation
committee, the organization and makeup of which is covered in detail later
in this chapter.
The second step in the product selection process addresses the situation in
which a change in the method of manufacture or control was implemented during
the last 20 or so production batches. The fact that a change has occurred
does not automatically disqualify the product for retrospective validation. One
must first know whether the particular modification has caused an expected
result to be different to the extent that it is no longer comparable to previous
batches. An example may be helpful. Suppose the method of granulating was
changed midway through the series of 20 batches selected for the validation
study. The number of batches representing the new process would be significantly
reduced and could be insufficient to capture some of the interactions that
can affect process reproducibility. In general, a history of any one of the follow-
Copyright © 2003 Marcel Dekker, Inc.
ing changes to the method of manufacture and control should be fully investigated
before any decision is made to validate retrospectively:
1. Formulation changes involving one or more of the active ingredients
or key excipients
2. Introduction of new equipment not equivalent in every respect to that
previously in use
3. Changes in the method of manufacture that may affect the product’s
characteristics
4. Changes to the manufacturing facility
A product found to be unsuitable for retrospective validation because of a
revised manufacturing process is a likely candidate for prospective validation,
which is beyond the scope of this chapter [1]. Such a discovery, however, should
be brought to the attention of the appropriate authority. In today’s regulatory
environment ignoring the matter would be imprudent.
The third and last step in our selection process is to identify which products
are likely to be discontinued because of a lack of marketing interest or
regulatory consideration, to be sold, or to be reformulated. The timing of these
events will dictate whether the product in question remains a viable candidate
for retrospective validation.
The foremost discussion on developing a list of suitable products for study
is summarized in Figure 1.
B. Organizing for Retrospective Validation
To this point we have produced a list of products that may be validated retrospectively;
that is, their manufacturing processes are relatively stable, and so
adequate historical data exist on which to base an opinion. The next consideration
is the formal mechanism for validating the individual products. Appropriate
organizational structures for effectively validating processes have been
put forth, but mostly in conjunction with the validation of new product introductions.
Still, these recommendations can serve as models. Because the products
being studied are marketed products, the quality assurance and production departments
can be expected to make major contributions. In fact, as far as retrospective
validation is concerned, it may be more appropriate for one of these
departments to coordinate the project. The research and engineering departments,
of course, will be needed, especially where recent process changes have
been encountered or equipment design is at issue.
Operating as a team, the previously discussed disciplines will determine
which data should be collected for each product and from how many batches;
subsequently, they will evaluate the information and report their findings. Personnel
resources beyond this committee are necessary to accomplish the tasks
Copyright © 2003 Marcel Dekker, Inc.
Figure 1 Selection of candidates for retrospective validation.
of data collection and analysis. The time requirements dictate that such work be
assigned to a function with discretionary time, possibly a technical services
group or a quality engineer. Management commitment is especially crucial if
disruptive influences are to be minimized. The loss of a committee member to
another project is such an example.
C. Written Operating Procedures
The various activities and responsibilities associated with retrospectively validating
a product must be put in writing. All too often this simple but crucial
step is omitted for the sake of expediency only to find at a later date that the
Copyright © 2003 Marcel Dekker, Inc.
initial assumptions cannot be recalled. Aside from maintaining consistency, a
written procedure to describe the work being performed satisfies the intent of
the current good manufacturing practice (CGMP) regulations.
In general, the written operating procedure should delineate in reasonable
detail how the validation organization will function. Not every situation can be
anticipated, and this should not be the goal. There should be sufficient detail,
however, to ensure consistency of performance in an undertaking that may continue
for several months. In the preparation of such a document, the following
questions should be answered:
1. Which organizational functions will be represented on the validation
committee?
2. What mechanism exists for validation protocol preparation and approval?
3. What criteria are used to select critical process steps and quality control
tests for which data will be collected?
4. How often will the committee meet to ensure prompt evaluation of
study data?
5. Who has responsibility for documenting committee decisions? For
report preparation?
6. Is there a provision for follow-up in the event of unexpected findings?
7. Where will the original study data and reports be archived?
In the preceding discussion of areas of interest to the validation organization,
two concepts were introduced that deserve further clarification: (1) critical
process steps and quality control tests that characterize the operation, and (2)
validation protocol.
1. Critical Process Steps and Control Tests
Critical process steps are operations performed during dosage-form manufacture
that can contribute to variability of the end product if not controlled. Since each
type of dosage form requires different machinery and unit operations to produce
the end product, the critical process steps will also differ. For each product
considered suitable for retrospective validation, a list of these steps must be
compiled following careful analysis of the process by technically competent
persons. In a similar manner, in-process and finished-product tests should be
screened to identify those that may be of some value. As a rule, tests in that the
outcome is quantitative will be of greatest interest.
A flow diagram of the entire operation, but particularly of the manufacturing
process, may be helpful in identifying critical steps, especially where the
process involves many steps. Such a diagram is also a useful addition to the
validation report prepared at the conclusion of the study.
Copyright © 2003 Marcel Dekker, Inc.
2. Validation Protocol
A written protocol that describes what is to be accomplished should be prepared
[5]. It should specify the data to be collected, the number of batches to be
included in the study, and how the data, once assembled, will be treated for
relevance. The criteria for acceptable results should be described. The date of
approval of the protocol by the validation organization should also be noted.
The value of a protocol is to control the direction of the study, as well as provide
a baseline in the event unanticipated developments necessitate a change in strategy.
A written protocol is also an FDA recommendation [1].
D. Other Considerations
Comprehensive records of complaints received either directly from the customer
or through a drug problem reporting program should be reviewed. Furthermore,
a record of any follow-up investigation of such complaints is mandatory [6] and
should be part of this file. Review of customer complaint records can furnish a
useful overview of process performance and possibly hint at product problems.
Complaint analysis should therefore be viewed as a meaningful adjunct to the
critical process step and control test selection process.
Batch yield reflects efficiency of the operation. Because yield figures are
the sum of numerous interactions, they fail in most cases to provide specific
information about process performance and therefore must be used with caution
in retrospective validation. In any event, this information should be collected,
as it can contribute to further refinement of the yield limits that appear in the
batch record.
Lot-to-lot differences in the purity of the therapeutic agent must be considered
when evaluating in-process and finished-product test results. In addition to
potency such qualities as particle size distribution, bulk density, and source of
the material will be of interest. Such information should be available from the
raw material test reports prepared by the quality control laboratory for each lot
of material received. The physical characteristics of the excipients should not
be overlooked, especially for those materials with inherent variability. Metallic
stearates is a classic example. In such instances, the source of supply is desirable
information to have available.
There is value in examining logs of equipment and physical plant maintenance.
These documents can provide a chronological profile of the operating
environment and reveal recent alterations to the process equipment that may
have enough impact to disqualify the product from retrospective validation consideration.
For this reason, it is always prudent to contemplate equipment status
early in the information-gathering stage. The availability of such information
should be ascertained for yet another reason: rarely is equipment dedicated to
Copyright © 2003 Marcel Dekker, Inc.
one product. More often than not, each blender, comminutor, tablet press, and
so forth is used for several operations. Information gathered initially can therefore
be incorporated into subsequent studies.
Retrospective validation is directed primarily toward examining the records
of past performance, but what if one of these documents is not a true
reflection of the operation performed? Suppose that changes have crept into the
processing operation over time and have gone unreported. This condition would
result in the validation of a process that in reality does not exist. It is therefore
essential to audit the existing operation against the written instructions. There is
obvious advantage to undertaking this audit before commencing data acquisition.
Ideally, the manufacture of more than one batch should be witnessed, especially
where multiple-shift operations are involved. The same logic would apply
to the testing performed in process and at the finished stage. If any deviation
from the written directions is noted, an effort must be made to measure its
impact. In this regard, the previously described validation organization is a logical
forum for discussion and evaluation.
As a rule, batches that are rejected or reworked are not suitable for inclusion
in a retrospective validation study [7]. Indeed, a processing failure that is
not fully explainable should be cause to rethink the application of retrospective
validation. Nonconformance to specification that is attributable to a unique
event–operator error, for example, may be justifiably disregarded. In such cases,
the batch is not considered when the historical data are assembled.
Raw materials, both actives and excipients, can be a source of product
variability. To limit this risk, there should be meaningful acceptance specifications
and periodic confirmation of test results reported on the supplier’s certificate
of analysis. Also, purchases must be limited to previously qualified suppliers.
A determination that such controls are in place should be part of any
retrospective validation effort.
III. SELECTION AND EVALUATION
OF PROCESSING DATA
The following discussion will focus on how to apply the previously discussed
concepts to the validation of marketed products. To provide a fuller understanding
of this procedure, the manufacture of several dosage forms designed for
different routes of administration will be examined. For each dosage form, critical
process steps and quality control tests will be identified. Useful statistical
techniques for examining the assembled data will be illustrated. It is also important
to note that not all of the collected information for a product lends itself to
this type of analysis. This will become more apparent as we proceed with the
evaluation of the five drugs under consideration.
Copyright © 2003 Marcel Dekker, Inc.
A. Compressed Tablet (Drug A)
Drug A is a compressed tablet containing a single active ingredient. Inspection
of the batch record reveals that the following operations are involved in the
manufacture of the dosage unit. The active ingredient is combined with several
excipients in a twin-shell blender. The premix just prepared is granulated using
a purified water-binder solution. The resulting wet mix is milled using a specified
screen and machine setting, then dried using either an oven tray dryer or a
fluid bed dryer. When dry, the blend is oscillated, combined with previously
sized lubricant, and blended. The granulation is then compressed. See Figure 2
for a flow diagram of the manufacturing process.
At the premix blending step, the batch record provides two pieces of infor-
Figure 2 Drug A: flow diagram of manufacturing process.
Copyright © 2003 Marcel Dekker, Inc.
mation: recommended blending time and blender load. The latter will be of little
interest, as only one size batch is produced for this product. Blender speed is
not specified in the batch record because it is fixed. Because mixing time has
been recognized as influencing blend uniformity, this operation will become the
first of the critical process steps for which we will want to collect historical
information [8].
The second major step is granulation. The process is controlled by the
operator, whose judgment is relied on for the appropriate end point. As no
information useful for process validation is available, we will move on to the
next step, comminution.
The batch record calls for passing the wet mix through a comminutor
using a no. 5 or 7 drilled stainless steel screen. Knife position and rotational
speed are two other factors that influence particle size; however, the step instruction
is quite specific about machine setup. Therefore, only screen size is a source
of variability for this step. We will want to know the frequency of use of each
screen.
Next, the granulation is dried to a target moisture of 1%. Either a tray or
fluid bed dryer may be used, at the discretion of area supervision. Regardless
of the method, drying time will be of interest. In addition, the final moisture
content should be ascertained for each batch. The dried granulation and lubricant
are then oscillated using a no. 10 or 12 wire screen. This is the last sizing
operation of the process; it will determine the particle size distribution of the
final blend. Knowing the history of use of each screen size is thus important.
The lubricant and granulation are blended for several minutes. The elapsed
mixing time is of interest because of its impact on drug distribution and the
generally deleterious effect of the lubricant on dissolution.
Because excess moisture is thought to have a negative effect on the dosage
form, loss on drying (LOD) is determined on the final blend.
Blending is followed by tableting. During compression, online measurements
such as tablet weight, hardness, and disintegration are made by the process
operator in order to ensure uniformity of the tablets. The weight of the
tablets is not measured individually; rather, the average weight of 10 tablets is
recorded. Although these data are good indicators of operation and machine
performance, we would prefer to have the more precise picture provided by
individual tablet weight.
Disintegration time and tablet hardness data could be collected from the
manufacturing batch records; however, for ease of administration these figures
will be obtained from the quality control test results, which also contain individual
tablet weighings.
Disintegration time was selected as a critical variable because for a drug
substance to be absorbed it must first disintegrate and then dissolve. The resistance
of a tablet to breakage, chipping, and so forth depends on its hardness.
Copyright © 2003 Marcel Dekker, Inc.
Disintegration, too, can be influenced by hardness of the tablet. For these reasons,
hardness testing results also will be examined.
Specifications used by quality control to release drug A are found in a
laboratory procedure. In addition to the previously discussed hardness and disintegration
time requirements, the procedure calls for determining the average
tablet weight by the United States Pharmacopeia (USP) procedure; that is, 20
individual tablets are weighed.
The control procedure also requires assay of individual tablets. Of all the
information available, these data will be the most useful in reaching an opinion
of the adequacy of the process to distribute the therapeutic agent uniformly.
In addition, the laboratory checks the moisture content of the bulk tablets.
It will be interesting to compare these results to the LOD of the final blend to
measure the contribution of material handling.
Critical manufacturing steps and quality control tests for drug A, identified
as a result of the review, are summarized in Table 1.
1. Evaluation of Historical Data
Earlier in the discussion of process validation strategies, 20 production batches
were suggested as a minimum number upon which to draw conclusions about
the validity of the process. In this particular example, however, two distinct
methods of drying are provided. In order to have sufficient history on each
operation, the number of batches examined was increased to 30.
The batches were selected so that the same number was dried by each
process. For the other critical manufacturing steps and release tests listed in
Table 1, data were collected for all 30 batches.
The first manufacturing step, premix blending time, was consistently reported
as 10 min, but with one exception. In this instance, the powders were
tumbled for 20 min, which is still within the limits (10 to 20 min) prescribed
by the batch record. It would be interesting to know if this source of variability
Table1 Drug A: Selected Critical Process Steps and Quality
Control Tests
Process steps Quality control tests
Premix blending time Disintegration time
Comminutor screen size Hardness
Drying time and method Average tablet weight (ATW)
Loss on drying (LOD)—granulation Assay
Oscillator screen size Water content-bulk tablet
Final mix blending time
LOD—final blend
Copyright © 2003 Marcel Dekker, Inc.
can materially affect attributes of the final product. Unfortunately, having only
one batch produced by the 20-min process does not permit statistically valid
comparisons. At best, test results for the single 20-min batch can be screened
using summary data from the remainder of the study. Under different circumstances,
batches would have been grouped by mixing time and compared by
dosage form attributes. More than likely, subsequent manipulation of the blend
would have negated any contribution, allowing us to conclude that a mixing
time of 10 to 20 min is not unreasonable.
At the wet milling step we encounter a situation similar to preblending;
that is, only two of the 30 study batches are prepared using the no. 5 drilled
screen. The no. 7 is obviously the screen of choice. The purpose of this step is
to produce particles of reasonably uniform size, which in turn will improve
drying. From the records, we also know that the no. 5 screen was used
only with batches that were tray dried. Elapsed drying time and residual
moisture were compared for the two batches from the no. 5 screen process
and the other 13 batches that were tray dried. No important differences were
detected. Still, in light of the limited use of the no. 5 screen, it would not
be inappropriate to recommend this option be eliminated from the processing
instructions.
Mean drying time for the oven tray process is 19.2 hr. All 15 batches
were dried within the specified time of 16 to 20 hr. No seasonal influence was
apparent. The average moisture content of these batches is 1.2%; the standard
deviation is 0.3%. The 15 batches dried using the fluid bed dryer had a residual
moisture of 0.8% (SD = 0.1%). Drying time is mechanically controlled and not
recorded. The statistics favor the fluid bed process; it is more efficient and
uniform. There is nothing in these data to disqualify the oven tray dryer from
further use, however.
Oscillation of the dried granulation and lubricant was accomplished in
every instance using a no. 10 wire screen. Reference to the no. 12 screen, the
alternative method for pulverizing the batch, must be deleted from the manufacturing
instructions for the process to be validated retrospectively.
The final mix blending time was reported as either 10 or 15 min. Twentyone
of the 30 batches were tumbled for 10 min and the remainder were mixed
for 15 min. The mixing time is not mechanically controlled or automatically
recorded; it is left to the operator to interpret elapsed time. Because of the
importance of the step to distribution of the therapeutic agent, a comparison was
made between the distribution of the percentage of relative tablet potency [(tablet
assay/tablet weight) ? 100] for the two mixing times. The frequency distributions
of the two populations are shown in Figure 3.
The two histograms are visually different, with the 15-min process exhibiting
more dispersion. Despite this difference both populations are tightly grouped,
which is a reflection of the uniformity of the blend.
Copyright © 2003 Marcel Dekker, Inc.
Figure 3 Histogram of drug A granulation uniformity resulting from different blending
times. Percentage of relative potency = (tablet assay/tablet weight) ? 100.
Copyright © 2003 Marcel Dekker, Inc.
The processes may be studied quantitatively by comparing the means and
standard deviations of the two populations. The effect of final blend time on
lubricant distribution was examined by comparing disintegration time statistics
for the grouped data. None was noted.
The moisture content of the 15 tray-dried batches following final mix
remained essentially unchanged from the drying step. The batches from the fluid
bed process gained moisture. This is probably attributable to handling very dry
material in a relatively humid environment. Both groups are still below the
target for this step of 1.5 %, however.
Table 2 gives a comparison of the moisture contents following the drying
and tumbling steps. The sizable increase in mean moisture content of the fluid
bed-dried batches deserves further study. To determine whether or not all
batches were uniformly affected, the mean moisture content was plotted in the
order in which the batches were produced. Whereas the plot for the tray-dried
batches is unremarkable, the fluid bed process chart (Fig. 4) depicts an unnatural
pattern. Further investigation discloses that heating, ventilation, and air condition
(HVAC) problems were experienced by the area in which a number of
these batches were blended.
During compression, 1000 tablets were randomly selected for use by quality
control. Inspection of the batch records revealed that all 30 batches were
compressed on the same model press operating at approximately the same speed.
All presses were fed by overhead delivery systems of the same design, thus
tableting equipment will not be a source of variability from batch to batch.
The test for disintegration is performed as described in the USP, and the
results are rounded to the nearest half-min. Disintegration time varied over a
narrow range for all batches studied. The 15-batch average for the tray dryer
process (2.7 min) is well below the specification (10 min) for this test. Hardness
of tablets from the tray dryer process averaged 15 Strong–Cobb units (SCU).
All batches exceeded the minimum specification (9 SCU); there is no upper
Table 2 Drug A: Comparison of Oven Tray Dryer and Fluid
Bed Dryer Processes
Oven tray Fluid bed
Test process (x?) process (x?)
Moisture dried granulation (%) 1.20 0.80
Moisture final mix (%) 1.10 1.30
Moisture bulk tablet (%) 1.26 1.50
Hardness, Strong–Cobb units (SCU) 15.00 16.70
Disintegration (min) 2.70 3.00
Copyright © 2003 Marcel Dekker, Inc.
Figure4 x?-control chart for drug A percentage moisture at final blend step (fluid bed
process).
limit. Hardness and disintegration time are not well correlated, probably due to
rounding of test results and the need to compare averages.
On average, tablets from the fluid bed process were slightly harder. Also,
the individual batches had a greater range of hardness than batches from the
alternative drying process. Disintegration time for the fluid bed process averaged
3.0 min. Individual batches ranged from2.0 to 4.5 min. As with the tray process,
no correlation was found between hardness and disintegration time. In summary,
tablets from the fluid bed dryer process were somewhat harder and took slightly
longer to disintegrate. (See Table 2.) These differences are considered insignificant,
however. If any recommendations were made, it would be to lower the
disintegration time specification or establish an internal action limit closer to
the historical upper range of the process.
Control charts were plotted for hardness and average tablet weight (ATW)
to evaluate process performance over time. Separate charts were prepared for
the tray dryer and fluid bed processes. Hardness values are an average of 10
individual measurements. The ATW subgroups are the result of weighing 20
tablets individually. The control charts were inspected for trends and evidence
of instability using well-established methods [9]. Only the control chart for hardness
of tablets from the fluid bed process responded to one of the tests for
pattern instability (Fig. 5); that is, two of three consecutive points exceeded the
2-sigma limit. From the chart it is obvious the general trend toward greater
tablet hardness (from 11 to 25 SCU) is the underlying cause of the instability.
The trend to greater hardness was subsequently arrested and may have to do
Copyright © 2003 Marcel Dekker, Inc.
Figure5 x?-control chart for drug A tablet hardness (fluid bed process).
with attempts to regulate another tablet variable—thickness, for example—
although the records are vague in this regard.
Water content of the bulk tablets irrespective of the drying process was
higher than at the final mix stage (Table 2). This is probably due to the compression
room environment and the low initial moisture of the powder. Still, the
specification limit of 2% is easily met.
The FDA has recently issued draft guidelines that recommend blend uniformity
analysis for all products for which USP requires content uniformity
analysis [10]. The USP requires this test when the product contains less than 50
mg of the active ingredient per dosage form or when the active ingredient is
less than 50% of the dosage form by weight. The concern FDA has is that if
blend uniformity is not achieved with mixing of the final granulation, then some
dosage units are likely not to be uniform [11]. Blend uniformity is not routinely
determined for drug A, nor is there a requirement because the dosage form is
over 50% active ingredient. In the absence of historical information about uniformity
of the blend, the relationship between tablet weight and potency should
be carefully examined.
Tablet weight should bear a direct relationship to milligrams of active
ingredient available where the final blend is homogeneous. This conclusion assumes
that demixing does not occur as the compound is transferred to intermediate
storage containers or to a tablet press hopper [12]. To measure the likelihood
that controlling tablet weight assures dosage uniformity, 50 tablet assays selected
at random (from 300 tablet assays) were compared to tablet weight using
regression analysis. Because the same model tablet press and blender were employed
for every batch, assay results from all 30 batches were pooled. The mean
purity of the 25 receipts of active ingredients used to manufacture the 30 batches
in the validation study was 99.7%, or 0.3% below target. Individual lots ranged
Copyright © 2003 Marcel Dekker, Inc.
from 98.8–102%. Because of these lot-to-lot differences, active ingredient raw
material potency was also included in the regression analysis.
The general model from the regression analysis is [13]
y = bo + b1X1 + b2Y2
where
y = tablet potency
bo = constant
X1 = raw material purity
X2 = tablet weight
Tablet potency was found to be related to raw material purity and tablet
weight as follows:
y = ?414.6 + 6.605OX1 + 0.4303X2
We would expect the regression plane to have a significant positive slope;
that is, as purity of the active ingredient and tablet weight increase, so will
tablet potency, and this was found to be the case. Both slopes are statistically
significantly different from 0 at ? = 0.025. When the above equation is used to
predict tablet potency given the ideal tablet weight (600 mg) for the product
and mean raw material purity of 99.7%, the resulting value is only 2.1 mg
different from the theoretical value of 500 mg.
In conclusion, drug A production was shown to be within established
specifications, and there is no reason to believe this will not be the case for
future production as long as all practices are continued in their present form.
Furthermore, there is no significant difference between batches produced by the
tray dryer process and the fluid bed process. A validation report should memorialize
these findings. The report should also recommend eliminating the option
to use a no. 5 screen for the wet milling step and a no. 12 screen to pulverize
the dried granulation. There is no experience or only limited experience with
this equipment that supports its continued availability. In the same vein, the
final blend time should be standardized at 10 min and automatically controlled
by means of a timer.
B. Coated Tablet (Drug B)
Let’s now turn our attention to a different dosage form, applying some of the
strategies developed during the examination of drug A. Again we want to identify
the process steps that are responsible for distributing the active ingredient
as well as the tests that measure the effectiveness of those actions. Drug B is a
sugar-coated tablet prepared in the traditional manner; that is, layers are slowly
built up around a core by applying a coat of shellac and then subcoating, gross-
Copyright © 2003 Marcel Dekker, Inc.
ing, and smoothing coats until specifications are met at each stage. In the case
of drug B, the core contains two active ingredients. The coating, on the other
hand, has no medicinal value and is intended solely to enhance the aesthetic
appearance of the product. The manufacturing process is shown in Figure 6.
Table 3 summarizes the selected critical steps for the manufacture of the
core tablet of drug B. The core is prepared by dry-blending the first active
ingredient (i.e., B1) with several excipients. Blend time is of interest for its
impact on the distribution of the therapeutic agent. The premix just prepared is
granulated using an alcohol-binder solution. The process directions allow the
operator some latitude in using additional alcohol to ensure that the batch is
uniformly wet. It will be necessary to know whether or not additional alcohol
is routinely required, and if so, how much is used. Besides measuring operator
technique, the wetting step affects particle size distribution. The oven tray dryer
is identified for drying the wet mix. Granulation drying time is of interest, because
loss on drying is not measured. Once dry, the granulation is milled using
a specified screen size and machine setting. Alternate equipment is not provided
for in the aforementioned steps.
The powder produced in the prior operation is combined with the second
active ingredient (B2), as well as several other excipients in a twin-shell blender
and mixed for several min. For reasons previously discussed, mix time is of
interest, and thus it is listed as a critical process step.
The blend of the two active ingredients (B1 and B2) is slugged and then
the slugs are oscillated. Slugger model and tooling are listed in the batch instructions.
The thickness of the slug is specified, but no information is recorded on
the slugging operation, as control of this procedure is left to the experience of
the press operator. The batch record permits the use of only one screen size.
Since all of the batches have been made in the same manner, this important
process step will not be included as one to be studied.
Next, lubricant and oscillated granulation are blended for several min. The
elapsed mixing time is of interest because of its impact on drug distribution and
the effect of the lubricant on dissolution. During compression, 1000 randomly
selected cores are accumulated for use by quality control.
The ATW, hardness, and disintegration time are determined by the press
operator during compression. As in the case of drug A, we will not rely on these
results for our study, but rather on the test data from quality control.
Following approval of the bulk cores by quality control, they are shellaccoated.
According to the manufacturing directions, one or two coats may be
applied based on the process operator’s judgment. A third coat is permissible
but only in response to directions from the supervisor. In any event, the actual
number of coats applied is recorded in the batch record. Because of its potential
impact on drug availability, this information is listed as a critical parameter in
Table 3.
Copyright © 2003 Marcel Dekker, Inc.
Figure 6 Drug B: flow diagram of manufacturing process.
Copyright © 2003 Marcel Dekker, Inc.
Table 3 Drug B: Selected Critical Process Steps and Quality Control Tests
Process steps Quality control tests
Premix blending time Average tablet weight (core and coated tablet)
Quality of additional alcohol used Hardness
Granulation drying time Disintegration time (core, shellacked core, and
Blending time to combine active coated tablet)
ingredients B1 and B2 Assay for active ingredients B1 and B2
Final blending time
Number of shellac coats
Number of build up costs
Coating pan temperature
Once the shellacking stage has been completed, the cores are built up
through a series of coating operations. The number of applications of coating
solution, the volume of coating solution applied, and the coating environment
can influence product performance and therefore need to be studied.
The quality control tests selected after review of in-process and finishedproduct
specifications are listed in Table 3. The rationale for selection has been
addressed in general terms during the review for drug A. These quality control
tests, while informative, provide no insight into how the shellac coating will
behave a number of years from now. For some perspective, we can examine the
stability profile of commercial batches placed into the stability program. Of
course, the batches considered would have been made by the same process as
the one being validated. Particular attention should be paid to disintegration and
dissolution results.
1. Evaluation of Historical Data
Only 19 batches of drug B are available for examination, one shy of the minimum
number previously suggested. The obvious course of action is to delay the
study until additional batches are produced. For reasons that will become apparent
later, the data analysis will be started with the batches immediately available.
Inspection of assembled data for the 19 batches of drug B confirmed that
premix blending was consistently performed for 15 min as specified in the manufacturing
directions.
On average, 11.5 kg of additional alcohol was needed to wet the premix
adequately. The actual quantity used ranged from 6 to 16 kg, and in no instance
was a batch produced without the use of extra alcohol. These data support an
increase in the minimum quantity of alcohol that is specified in the manufacturing
directions.
Copyright © 2003 Marcel Dekker, Inc.
Granulation drying time was unremarkable. All 19 batches were dried
within the specified time of 12 to 16 hr; the mean time was 13.4 hr, and no
trends, seasonal or otherwise, were detected.
The operator is instructed to combine the premix containing active ingredient
B1 with active ingredient B2 and blend for 30 min. All 19 batches were
handled as directed in the batch record. Oscillation of the slugs back to powder
was accomplished in every case using the screen listed in the batch record. For
final granulation, we found that each batch was blended for 30 min, as directed.
There is no blend uniformity testing.
Once the cores are compressed, one to three sealing coats may be applied
by the process operator. The third coat was never required, however. All 19
batches were completed with two coats of shellac. The volume of shellac applied
was always 350 mL for both steps, as required by the batch record, and the
record further indicates that the temperature of the air directed into the coating
pan was always set at 40°C. There is no record of the temperature being monitored,
however. The shellacked cores were dried overnight at 35°C. The dryer
temperature was tracked and automatically recorded; no variablity was encountered
when the temperature chart was reviewed.
The marketable dosage unit is arrived at by the slow buildup of layers on
the shellacked core through the hand application of coating solution. This finishing
step is intended solely to enhance appearance by concealing surface irregularities
and should have no effect on drug delivery. The three coating solutions
are compounded as part of the batch process and immediately prior to being
needed. The directions call for the subcoating solution to be held at 65°C ± 2°
following compounding and applied at this temperature. Up to five applications
are permissible to achieve the tablet target weight of 380 mg; however, for the
19 batches in this study either three or four coats were applied. The impact of
varying the number of solution applications was studied by forming the batches
into two populations. Mean tablet weight, total volume of solution applied, and
mean disintegration time were compared. Unfortunately, the only available disintegration
measurement was from a test run on the fully built-up tablet (Table
4). The tablets from batches with three applications of subcoat solution had
slightly lower weights on average (6 mg), relative to the other group. The volume
of coating solution varied considerably by application (475 to 700 mL),
and the total volume was slightly lower when there were only three applications.
Mean disintegration time of the groups differed by less than 30 sec, which is
insignificant, given the test methodology.
Additional layers are added to the tablet using a grossing solution that is
similar to the subcoating formula and contains a colorant. As many as 15 applications
may be needed to achieve the target weight of 450 to 490 mg. Warm
air (32–38°C) is applied between coats to achieve drying. A dial thermometer
is visible to the operator, but there is no requirement to log the actual tempera-
Copyright © 2003 Marcel Dekker, Inc.
Table4 Drug B: Comparison of Mean Hardness
and Distintegration Times
Disintegration time (min)
Batch Hardness Core Shellacked Coated
number (SC units) tablets cores tablets
01 11 8 15 22
02 10 9 20 25
03 10 8 19 21
04 11 9 16 22
05 8 8 13 17
06 8 8 14 18
07 8 7 14 21
08 9 8 14 20
09 8 8 15 20
10 10 8 17 19
11 12 9 13 20
12 12 8 13 20
13 8 7 14 17
14 8 7 13 18
15 12 8 13 18
16 10 11 17 23
17 11 9 20 26
18 10 8 18 20
19 9 7 14 19
x? 9.74 8.16 15.37 20.32
RSD 15.30 11.76 15.81 12.15
ture. In the manner previously discussed, the total number of applications, volume
of solution consumed, and tablet weight achieved were analyzed. Variability
was present between batches, but populations that received different treatment
were quite similar with respect to tablet weight and disintegration time (as measured
at the finished tablet stage).
A finishing solution is used to bring the tablet to its final weight. The
operation is very much as previously described except that fewer coats are applied
and therefore less weight is added. An analysis of the data would follow
the strategy just discussed.
Let’s next direct our attention to the testing done by quality control. The
ATW at the core stage is based on the results from weighing 20 randomly
selected tablets. The control chart in Figure 7 depicts a process with no single
Copyright © 2003 Marcel Dekker, Inc.
Figure 7 (A) x?-control chart of drug B average tablet weight (core stage). (B) x?-
control chart of average coated tablet weight for drug B.
value outside the upper control limit (UCL) or the lower control limit (LCL).
Other tests for instability show the process to be operating normally. All 19
batches were compressed on the same model press, according to the batch record.
The ATW for the coated tablet is shown for comparison. Correlation between
core weight and finished tablet weight is poor. Such fluctuations would
be expected of a manual coating operation intended solely to enhance pharmaceutical
elegance, nevertheless the control chart did not respond to our tests for
patterns of instability (Fig. 7).
Disintegration time is measured at three steps in the process: at compression,
after application of the second shellac coat, and at finished product release.
Table 4 compares the values of mean hardness obtained for 10 individual cores
to the disintegration times for the core, shellacked core, and coated tablets. No
Copyright © 2003 Marcel Dekker, Inc.
relationship was found between core hardness and uncoated core disintegration
time. The 5-min increase in mean disintegration time from shellac coated core
to finished tablet is a measure of the contribution made by the finishing steps.
Receipts of active ingredient raw materials B1 and B2 are accepted by
quality control based on standard tests for potency, chemical attributes, and
particle size. Particle size is determined by sieve analysis. Unfortunately, this is
a limit test in which 99% of the sample must pass through a certain mesh screen,
therefore any influence particle size distribution might have on dosage form
potency cannot be examined.
Figure 8 is a plot of mean assay results for active ingredient B1. Drug
potency (200 mg per tablet) is measured in duplicate from samples obtained by
grinding a composite of 20 randomly selected tablets. Figure 8 is also influenced
by the variability of the purity of the raw material, which ranged from 97.6–
99.5%.
Nevertheless, the pattern was unresponsive to our standard tests for process
instability, and individual batch results were well within established control
limits for this product (180 to 220 mg). The grand mean of 99.0% is 2.0 mg
below the theoretical tablet potency, probably because of below-target purity of
the active ingredient raw material.
Content uniformity testing is not a requirement for drug substance B1,
hence no information is available about the weight of the active ingredient in
individual dosage units. With so much emphasis today on demonstrating adequate
control over this variable, a one-time study run concurrently with the next
production should be considered. Kieffer and Torbeck suggest two statistical
Figure 8 x?-control chart for drug B tablet assay (ingredient B1).
Copyright © 2003 Marcel Dekker, Inc.
techniques—the tolerance interval and capability index (Cpk)—may be used to
demonstrate uniformity of the drug substance in the dosage form [14]. The
starting point is to assay individually a representative sample of tablets (e.g.,
30) from a series of batches. Regression analysis also can be performed to assess
the influence of tablet weight and raw material purity on potency with the availability
of data for individual tablets.
Active ingredient B2 (25 mg per tablet) is measured on 10 individual
tablets per batch. We randomly selected 50 tablets from the 19 batches for use
in regression analysis. Because purity of the raw material varied from 98.4–
99.7%, it was included as the second variable. Our predictor equation for tablet
potency (y) is
y = ?51.10 + 0.5342X1 + 0.0752X2
where
X1 = raw material
X2 = tablet weight
The slope of the regression plane was found to be positive for both tablet
weight and raw material purity, as we would expect. The slope for tablet weight
was statistically significantly different from 0 at ? = 0.01, while the slope for
purity was significant at ? = 0.05.
Substituting the ideal tablet weight (at the core stage) of 320 mg and mean
raw material purity of 99% in the above equation yielded a tablet potency of
25.85 mg, or 0.85 mg greater than theoretical. The predicted tablet potency is
close to the ideal and well within specification limits (22.5 to 27.5 mg). It is
possible this outcome was influenced by differences arising from the method of
determining the purity of the raw material and the potency of the dosage form.
The former is a wet chemistry analysis, whereas the potency of the drug in the
finished tablet is determined by use of an automated procedure. Unfortunately,
we were unable to quantify this difference.
The process for drug B has been shown to operate within narrow limits
and yield finished dosage forms that are therapeutically equivalent, as measured
by standard product release criteria. There is no reason to believe subsequent
batches will perform differently as long as all conditions remain static. Despite
this generally favorable prognosis, additional work is necessary to provide the
assurance of process reliability expected today.
1. There remains the unanswered requirement to demonstrate blend uniformity
of active ingredients B2. This issue might be addressed by
testing the blends of a series of batches until sufficient data are accumulated
to consider the process reliable. Hwang et al. have provided
some insight into establishing an in-process blend test [15]. The vali-
Copyright © 2003 Marcel Dekker, Inc.
dation committee might also suggest that an individual tablet assay
be performed for active ingredient B1 during this period. The aforementioned
statistical treatments would then be employed to demonstrate
that tablet potency is well controlled.
2. Only 19 batches of drug B were considered suitable for the validation
study. This number is shy of our stated goal of a minimum of 20
batches. We therefore will want to supplement the data from the original
19 batches. This effort should be coordinated with the blend uniformity
testing.
3. Details of the slugging step need to be improved, both to assure consistency
and to facilitate third party monitoring. All of these recommendations
should be memorialized in the validation report.
C. Softgels (Soft Gelatin Capsules; Drug C)
This dosage form consists of a solution of active ingredient encased within a
spherical, plasticized gelatin shell. Unlike hard gelatin capsules, for which several
discrete operations are required to produce the final product, the softgel is
formed, filled, and hermetically sealed in one continuous operation [16]. Molten
gelatin mass is formed into two sheets or ribbons, each of which passes over a
die of the desired size and shape. At the point at which the two rotating dies
meet, the hemispheres are sealed and simultaneously filled with the solution of
active ingredient. Next the capsules are cleaned by immersion in an organic
solvent, dried, and inspected. (See Fig. 9.)
According to the process instructions, the active ingredient powder is dissolved
in vegetable oil with the aid of a solubilizer. Blend time is stated as 25
to 30 min. This is an elapsed time. Because a range of time is permitted, this
step is one for which historical data will be sought (Table 5). The bulk solution
is assayed to confirm that the prescribed weight of drug C was charged and
dissolution is complete before capsule filling may proceed. Concentration of the
active ingredient should vary very little from one batch to another with such a
straightforward process. We will want to confirm that this is the case. The purity
of each active ingredient raw material receipt is also of interest for reasons
previously stated.
The instructions for gelatin mass preparation direct that gelatin powder be
blended with water, a plasticizer, and colorant until a uniform consistency is
achieved, then heated until molten. The recommended blend time is 20 min at
a temperature of 60°C ± 5°. The temperature of the molten gelatin just prior to
formation into a ribbon is critical; too high a temperature causes the gelatin to
deteriorate, and a low temperature affects flow rate. Both conditions are to be
avoided for their deleterious effect on capsule formation. For these reasons,
Copyright © 2003 Marcel Dekker, Inc.
Figure 9 Drug C: flow diagram of manufacturing process.
gelatin mass temperature is listed in Table 5. Blend time is of interest, too, as a
measure of process and raw material performance.
An important specification for gelatin is bloom strength, a quality of the
raw material that determines whether or not a capsule can be formed and sealed.
As with active ingredient purity, we will want to know this value for each lot
of gelatin used in the validation study.
Speed of die rotation and gelatin ribbon thickness are two important machine
conditions that are included in Table 5. The rationale of their selection is
Table 5 Drug C: Selected Critical Process Conditions
and Quality Control Tests
Critical process conditions Quality control tests
Blend time to solubilize active ingredients Bulk assay
Gelatin mass mix time and temperature Dissolution
Die rotation speed Average fill weight
Gelatin ribbon thickness Dosage form assay
Relative humidity of encapsulation room Microbial content
Copyright © 2003 Marcel Dekker, Inc.
as follows: die rotation speed controls dwell time. If there is insufficient contact
time, the capsule halves will not properly seal. Subpotent softgels may result
from loss of liquid fill through a poorly developed seam. Gelatin ribbon thickness
determines capsule wall and seam thickness. Insufficient thickness will
contribute to poorly formed capsules and leakers. An overly thick ribbon results
in shell sealing problems. Ribbon condition is influenced by the temperature of
the gelatin mass, as previously noted. Relative humidity in the encapsulation
room is important to efficient drying. Minimally, we will want to know the
room condition during the time in which the 20 batches in this study were manufactured.
It would be best to examine environmental conditions over a longer
time period, say 1 year, to capture seasonal trends should they exist.
The batch record instructs the encapsulation machine operator to measure
and record seam and wall thickness every 45 min. Softgel weight is also checked
periodically by this operator. This information could be useful in demonstrating
process control but to a large extent seam and wall thickness are controlled by
manufacturing conditions for which historical data are already being sought. For
this reason, the results of these in-process monitors need not be pursued initially.
Consistent with the approach taken for other dosage forms previously discussed,
finished softgel weight data can be obtained from quality control reports when
dissolution and assay results are collected.
1. Evaluation of Historical Data
The first step in the production sequence is solubilizing the active ingredient in
an appropriate volume of vehicle. For drug C, this blend is a solution, and the
activity was routinely accomplished in the prescribed time (25 to 30 min). The
analytical test results of each bulk batch confirmed that small differences in mix
time had no impact. The nine receipts of active ingredient raw material used to
prepare the 20 batches under review had a mean potency of 99.5%. Individual
receipts ranged from 98.7–102%. No trends were noted when these receipts
were examined graphically.
Gelatin mass preparation time was recorded as being between 17 and 23
min. Such small differences were not thought to be worthy of further consideration.
Gelatin mass temperature is critical for reasons previously noted. The
temperature range achieved during compounding was examined by means of the
recorder charts for evidence of equipment problems and lack of operator attention.
The degree of variability within a batch and from batch to batch was
considered reasonable for an operator-controlled process of this type. Mass temperature
at the end of compounding, just before the start of encapsulation, averaged
60.5°C. Individually, all batches met the specifications of 60°C ± 5°. Control
over gelatin mass temperature for the duration of the filling operation was
generally unremarkable, although larger fluctuations were present for four of
Copyright © 2003 Marcel Dekker, Inc.
the 20 batches in the latter stages of filling. The cause of these fluctuations was
not apparent, however.
A bloom strength determination is part of the acceptance criteria for each
receipt of gelatin raw material. The bloom gelometer numbers range from 125
to 195 for the 12 lots, with a mean of 147. This number was compared to
gelatin ribbon thickness and die rotation speed during encapsulation to ascertain
whether lot-to-lot differences had to be compensated for. No relationship was
found.
Encapsulation machine setup specifications were considered for their impact
on softgel seam and wall formation. Die speed is given as 4.0 rpm± 0.2.
Gelatin ribbon thickness is to be controlled at 0.032 in. ± 0.003. More than one
machine was used to produce the 20 batches; however, they were all the same
make and model. Machine settings during encapsulation are summarized in Table
6. Slight machine-to-machine differences are present, but all three operations
are easily within suggested settings for this product. On average, gelatin mass
temperature was the same for each encapsulation machine.
The influence of gelatin mass temperature, gelatin ribbon thickness, and
die speed on softgel formation and the interactions of these variables were explored
by regression analysis as follows:
Finished softgel weight = gelatin mass temperature + die speed
+ gelatin ribbon thickness
The outcome was inconclusive, probably due in part to use of data that did not
take into consideration the variability in fill volume.
Quality control release testing was performed on a sample taken from
1000 softgels randomly selected at the conclusion of processing. The outcome
of dissolution, assay, and average fill weight tests is reported in Table 7, along
with the corresponding specification. These data were analyzed using methods
previously illustrated. In addition, all batches passed the microbial limits test.
Table 6 Drug C: Encapsulation Machine Settings
(Die Speed and Ribbon Thickness)
Die speed Ribbon thickness
Machine number/batches (x?; rpm) (x?; in.)
All machines (N = 20) 4.01 0.032
Machine 1 (N = 7) 3.93 0.032
Machine 2 (N = 7) 4.07 0.031
Machine 3 (N = 6) 4.02 0.033
Copyright © 2003 Marcel Dekker, Inc.
Table7 Drug C: Quality Control Release
Specifications and Results
Test Specification Result (x?)
Dissolution (%) NLT 75% 89.1
Average fill weight (mg) 855–945 901.7
Assay (mg) 475–525 516.2
Dissolution and average fill weight results are not remarkable. Active ingredient
assays averaged 16 mg above midpoint of the specification, which is
not assignable to raw material purity which averaged 99.5%. Examination of inprocess
checks of wall thickness showed this parameter to be under control at
all times, effectively ruling out fill volume as a factor. One explanation could
be the manner in which the active ingredient solution is prepared. It is noteworthy
that all 20 batches exceed the midpoint of the bulk solution specification.
Individual batches range from 509 to 523 mg when expressed in terms of target
fill weight (900 mg). This distribution suggests that a condition common to all
the batches is part of the explanation. The analytical methodology used to release
the bulk and finished dosage form would be a good place to start such an
investigation.
Available information reveals a process that is consistently reproducible
and can be considered validated on that basis. Before doing so, however, the
assay results should be justified and the outcome of this investigation included
in the validation report.
D. Solution Dosage Form (Drug D)
The solution dosage form to be discussed is an elixir. A review of the batch
record shows that it contains two active ingredients (D1 and D2). The different
steps in preparing the dosage form are outlined in Figure 10.
Drug D may be produced in both 1000- and 2000-gal batches to meet
inventory requirements. Major equipment and operator instructions are the same
regardless of batch size. The only difference is the amount of each ingredient
charged to the make tank. With a formulation such as this, there is little likelihood
that batch size is an important process variable. Nevertheless, we will be
conservative and treat each size batch as a unique process. An alternative strategy
would be to validate the 2000-gal process and demonstrate for the 1000-gal
batch the adequacy of mixing, using, for instance, assay data.
The batch is prepared using a single tank. Large-volume liquid excipients
and deionized water are metered into the main tank. The other materials are
Copyright © 2003 Marcel Dekker, Inc.
Figure 10 Drug D manufacture: flow diagram showing major sequences of steps as
described in Manufacturing Batch Record. The numbers indicate the order in which the
process is carried out.
preweighed. Final yield is calculated from a freeboard measure of the bulk liquid
in the holding tank. Variable-speed agitation is available; however, the batch
instructions do not require the rate of mixing to be adjusted from step to step,
nor are temperature adjustments needed to get the solid raw materials into solution.
A standard filter press is employed to clarify the batch just prior to transfer
to the holding tank, thus the only variable information available from the batch
record is the time required to accomplish such steps as addition, mixing, and
dissolution of raw material active ingredients in vehicles. Although the elapsed
time to perform these steps is identified in Table 8 as a process variable to
be considered, this information is useful only as a crude measure of operator
performance.
Yield at the conclusion of processing is available from the batch record
and is identified in Table 8 as an important step. Yield data are potentially
Copyright © 2003 Marcel Dekker, Inc.
Table8 Drug D: Selected Critical Process Steps and Quality Control Tests
Process steps Quality control tests
Elapsed time to complete steps A, B, andC Appearance
Batch yield pH
Specific gravity
Viscosity
Alcohol (% v/v)
Assay of active ingredients D1 and D2
useful in explaining atypical quality control test results; they also provide a
rough measure of equipment condition and operator technique.
The quality control test results for each batch are relied on almost exclusively
for the critical information used in this study. The rationale for selecting
the finished dosage form parameters listed in Table 8 is as follows.
The physical appearance of the finished product is a good indicator of the
adequacy of the filtration step. Although it is only a subjective test, it does
provide information on equipment performance. The pH of the finished dosage
form is critical for the stability of active ingredient D1, hence its measurement
is warranted. Specific gravity reflects the quantities of ingredients charged, as
well as adequacy of the mixer to distribute them uniformly. A viscosity check
is performed to ensure that no untoward viscosity buildup has occurred that
could affect pourability. Viscosity of the end product can also indirectly indicate
the quality of the dispersion of the viscosity-building agent. Determination of
the quantity of alcohol in the end product is critical as well, because the solubility
of one of the active ingredients, D2, depends on the concentration of alcohol.
Also, because alcohol can easily be lost during processing, any values below
the established limit would be evidence of a problem associated with the process.
Finally, concentration of the active ingredients is measured. These data
attest to the adequacy of both the dissolution of each ingredient and the subsequent
mixing during phase combination. Any major deviation from established
limits would indicate problems in manufacturing. Because raw material active
ingredient purity is known to vary from one receipt to the next, it too should be
included in any review of dosage form potency.
1. Evaluation of Historical Data
The time required to accomplish mixing and addition steps is summarized in
Table 9. The differences in elapsed time were thought to reflect those typically
encountered in manual operations. Batch yield is also shown in the table for
future reference.
Copyright © 2003 Marcel Dekker, Inc.
Table9 Available Process Information Gathered from Batch
Records for the Manufacture of Solution (Drug D) Dosage Form
Time required for the
completion of the step
(in hr and min)
Batch Step Step Step Batch
number Aa Bb Cc yield (%)
01 5:00 1:05 1:30 99.10
02 5:00 0:40 1:10 99.20
03 6:00 0:40 1:00 100.10
04 5:00 1:10 1:20 98.50
05 4:30 0:50 1:15 99.20
06 5:00 1:05 1:10 98.90
07 6:00 1:15 1:40 98.95
08 5:30 0:45 1:30 98.50
09 6:00 1:00 1:35 98.60
10 4:30 0:45 1:20 98.87
11 5:30 1:00 1:25 98.81
12 5:45 0:50 1:25 98.70
13 5:00 1:00 1:30 99.20
14 5:00 1:10 1:40 98.95
15 6:00 1:15 1:20 99.02
16 5:00 0:45 1:00 99.40
17 5:00 1:00 1:05 99.50
18 6:00 0:50 1:30 99.10
19 5:00 0:40 1:10 99.48
20 5:00 1:05 1:25 99.30
x = 99.07
aStep A: Time required to disperse viscosity-building agent in water.
bStep B: Time required to dissolve water-soluble formulation ingredients
in water.
cStep C: Time required to dissolve alcohol-soluble formulation ingredients
in alcohol.
Product appearance was unremarkable. The pH was examined using a
control chart. Because this is a single point observation, the moving range
method was employed. The chart disclosed that the process operates within the
calculated control limits. No trends were apparent. Individual batch results all
met specification, and the process average (4.07) is close to the target value of
4.10. (See Fig. 11.)
Copyright © 2003 Marcel Dekker, Inc.
Figure 11 x?-control chart of pH using moving range method for drug D.
The mean specific gravity for this 20-batch study is 1.091, the midpoint
of the specification range. The control chart for this variable was prepared by
the moving range method (Fig. 12). The calculated UCL and LCL (1.0914 and
1.0888, respectively) are within the product’s specification limits. Individually,
all batches met specification. The specific gravity of batch 3 is at the lower
control limit. A plausible explanation for this can be found in the bulk yield
(Table 9), which is 0. 1%greater than theory and 1.03%in excess of the average
for this study, hence “overdiluting” the batch during manufacture is a possible
explanation. The alcohol concentration of batch 3 should be compared to the
20-batch mean to determine whether or not this step was the cause.
The alcohol content averaged 15.09%, or 0.09% above target. Individual
batches met specification in every instance. The control chart (Fig. 12) was
unremarkable in terms of trends or tests for pattern instability. Batch 3 is slightly
below the process average, effectively ruling out overaddition of alcohol as a
factor in the low specific gravity previously observed.
The concentration of active ingredient D1 for batch to batch is shown in
Figure 13. The mean potency of all batches is 0.1 mg/5 ml above target. The
control chart did not respond to tests for unnatural patterns and trends. It is
noteworthy that the calculated UCL (16.7 mg/5 mL) for the 20 batches in this
study exceeds the release specification for the product (15.5 to 16.5 mg/5 ml.
A probability thus exists that a batch may eventually fail to meet the release
criteria. Raw material purity is not a factor in the potency of an individual batch
because it is taken into consideration at the time of manufacture. A possible
explanation for the wide historical control limits is the assay methodology for
Copyright © 2003 Marcel Dekker, Inc.
Figure 12 (A) x?-control chart for drug D specific gravity using moving range method.
(B) x?-control chart of drug D alcohol percent (v/v).
D1. As a starting point, the next 20 production batches could be monitored for
this variable to see whether or not the condition persists.
Assay results for active ingredient D2 individually met specification. The
20-batch average was 126.3 mg/5 ml, or 1.3 mg/5 ml in excess of target. Inspection
of the x?-control chart for this variable (Fig. 13) discloses an atypical pattern;
that is, batches 1 to 6 have distinctly greater potency than batches 7 to 20, with
the exception of batch 14. The biomodality of the data is readily apparent when
batch 14 is disregarded. The phenomenon can be explained by a change in
assay method from ultraviolet (UV) to high performance liquid chromatography
Copyright © 2003 Marcel Dekker, Inc.
Figure 13 (A) x?-control chart for drug D1 potency. (B) x?-control chart for drug D2
potency.
(HPLC), commencing with batch 7. Further investigation revealed that the UV
procedure was used for batch 14 as well, in this instance because the HPLC
instrument was out of service. With the two populations properly grouped, consistency
of the HPLC method to detect ingredient D2 becomes apparent. (See
Table 10.)
Eleven receipts of active ingredient D2 were used to compound the
batches included in the study. Lot purity ranged from 99.5–101.1%; the average
was 100.4%. Purity of the raw material receipt was not seen to have an affect
on the potency of the batch(es) in which it was used. This is probably due to
the occasional need to use more than one receipt to compound a batch.
In summary, the study demonstrates the wisdom of switching to an HPLC
method for finished bulk approval. It also raises questions about the reproducibility
of the assay for drug D1, which should be investigated, otherwise no
Copyright © 2003 Marcel Dekker, Inc.
Table 10 Drug D: Comparison of UV and HPLC
Assay for Active Ingredient D2
Test method
Statistic UV HPLC
N 7 13
x? 129.07 124.79
s 2.44 0.70
recommendation for change in the method of operation can be made based on
historical results from selected manufacturing steps and control tests. Furthermore,
with a better understanding of the cause of drug D1 potency variability,
it is not unreasonable to conclude future production will continue to meet specifications.
E. Semisolid Dosage Form (Drug E)
The product we have selected for examination is an emulsion cream of the oilin-
water type. We will refer to this product as drug E. The directions for manufacture
call for addition of the active ingredient to a methylcellulose solution,
followed by addition of an humectant.
Heat is applied with continued mixing until a specified temperature is
reached. Consistency is then increased through the introduction of several viscosity-
building agents. Occlusives and preservatives are then incorporated. The
batch is held with agitation at this temperature for several min and then cooled
with varying rates of agitation to prevent air entrapment.
Table 11 lists the critical process steps that should be considered for evaluating
batch-to-batch uniformity. Although other information such as melting
Table 11 Drug E: Selected Critical Process Steps and Quality Control Tests
Process steps Quality control tests
Rotational speed of the inner and outer sweep blades during Appearance
processing pH
Total time required to increase the batch temperature to 65°C Assay
Time required to achieve batch cool-down (65–35°C) Specific gravity
Penetrometer reading
Microbial contents
Copyright © 2003 Marcel Dekker, Inc.
time for waxes is available from the batch record, those were not thought to be
critical.
Also included in Table 11 are six tests routinely performed by the quality
control department on a sample of the bulk. The sample is obtained about midway
during transfer of the bulk from the make tank to the storage totes. The
appearance of the product was selected as an indicator of filter performance. A
stable pH, within specification, is essential to preclude degradation of active
ingredient and obviate dermal irritation. Specific gravity, which is a measure of
the amount of suspended solids, indicates that all formulation ingredients have
been incorporated. Penetrometer readings measure the consistency of the cream,
which may affect the ability to package the product as well as acceptance by
the patients. Microbial content is determined routinely in the interest of the
safety of the patients as well as product efficacy. Finally, the assay of the active
ingredient is selected as a measure of the efficiency of the process to distribute
the drug uniformly.
1. Evaluation of Historical Data
A review of the records for 20 batches shows that the rotational speed of the
inner and outer sweep blades in the manufacturing vessel is always set at 24 to
20 rpm, respectively, during the heating cycle. Statistical treatment was therefore
considered inappropriate. During the cooldown cycle, the batch record
specifies rotational speeds of inner and outer sweep blades. It also allows the
operator to change the agitator speeds to prevent aeration and instructs the operator
to record any such changes. The review shows that no adjustments were
necessary. Because of the consistency of the operation from batch to batch, no
statistical treatment of the available data was deemed necessary.
The time required to increase the batch temperature to 65°C was studied.
Of the 20 batches, 18 required 35 min, while the other two batches attained the
desired temperature in about 30 min. Such small differences were not thought
important enough for further evaluation. The time required for the cooldown
cycle was found to be 65 min for 16 batches, while four batches took 60 min.
Final product characteristics, such as appearance and penetrometer readings,
were compared for batches with cooling times of 60 and 65 min, and no difference
was found in the end product.
Data collected from the quality control tests were evaluated next. The
assay for active ingredient varied from 19.60–19.90%, indicating a yield of
98–99.5% of the original quantity added. Some of this loss is assignable to the
purity of the raw material active ingredient, which ranged from 99–100%. These
assay values also indicate that the active ingredient is well distributed in the
cream, and that loss of the active ingredient during the various processing steps
is negligible. The specific gravity of the batch varied from 1. 120 to 1. 126, a
Copyright © 2003 Marcel Dekker, Inc.
good indication that the level of solids from batch to batch is consistent. The pH
of the end product varied from 5.4 to 5.9. This variability may be partly attributed
to the difference in pH of the excipients and/or the deionized water used.
Unfortunately, the pH of purified water was not always available for the date on
which a batch of drug E was compounded. Similarly, pH is not a routine quality
control test for several of the excipients, thus further investigation was not possible.
Data from the quality control tests for the various parameters selected
were used to prepare control charts. These control charts were then analyzed for
any evidence of instability or unnatural pattern. None was detected.
A microbial limit test was performed on a routine basis and the 20 consecutive
batches each showed conformance to specifications.
One recommendation arises from the review of this product. The rotational
speeds of the agitator were remarkably constant during the heating cycle
and therefore should be included in the written instructions for future batches;
otherwise, the process is considered validated.
IV. COMPUTER-AIDED ANALYSIS OF DATA
Once the mechanics of retrospective validation are mastered, a decision is required
as to how data analysis will be handled. The illustrated calculations may
be performed manually with the help of a programmable calculator and the
control charts may be hand-drawn, but computer systems are now available that
can shorten the task. If the computer route is chosen, commercially available
software should be considered. There are many reasonably priced programs that
are more than up to the task [17].
Before beginning data analysis, the following issues should be considered:
1. The vertical scale has to be chosen carefully to accommodate both
control and specification limits. The latter may have to be entered
manually to avoid unreasonable compression of the chart.
2. Care must be taken that tables and graphics are fully identified as to
product name and the variable(s) under review.
3. Manual examination of some information should be anticipated. The
output will have to be interpreted and related to other factors that may
not be part of the database. Nonnumerical information is an example.
Figure 14 illustrates the construction of a table containing the results of
end-product testing of 22 batches of a tablet dosage form. For simplicity, the
product will be referred to as drug F. There are 22 rows and 14 columns, for a
total of 308 data points. Each column has an abbreviated heading that describes
the information contained therein. The headings are not needed for computer
Copyright © 2003 Marcel Dekker, Inc.
Figure 14 Drug F: product release test results organized for computer analysis.
Copyright © 2003 Marcel Dekker, Inc.
analysis, but make manual review possible. The 22 batches, one per row, have
been assigned a reference number (1 to 22) to simplify control chart preparation.
The batch and formula numbers are listed next for information only, in the event
that further manual investigation of a conclusion is deemed appropriate. Columns
3 through 12 (except 11) contain mean results for tests performed by the
laboratory: percentage of LOD, dissolution (for two active ingredients), ATW,
hardness, percentage of friability, assay, and dose uniformity (DU). Column 11
describes the assay method employed for active ingredient 2. The number 1 was
assigned to the UV assay procedure, and the number 2 refers to the HPLC
method. This is one solution for including nonnumerical information in the database.
Column 14 lists the results of the inspection for capped tablets. The numbers
shown reflect the actual number of capped tablets recovered from a random
sample of a given size. Figure 14 could easily be expanded to incorporate other
variable information, such as observations about critical process steps, which
might be needed for the validation.
Data analysis would normally commence with the calculation of means
and standard deviations for each column of numbers where this was appropriate.
Next, tests would be performed to establish whether or not the data were normally
distributed. The data could then be grouped according to a particular
variable (e.g., year of manufacture, oscillator screen size, or assay method) and
compared statistically for differences between the mean and standard deviations.
For ease of review by the validation team, a table should be printed summarizing
the statistics calculated and the conclusions reached as a result of these data
manipulations.
Graphical methods are powerful tools for extracting the information contained
in data sets and making statistical conclusions easier to understand. A
variety of techniques have been developed in recent years. An excellent overview
of these methods is given by James and Polhemus [18].
Figure 15 is a scatter plot of ATW versus assay using data from columns
6 and 9 of Figure 14. It was prepared using commercially available software.
The scatter plot enables the reviewer to visualize the relationships among two
or more product characteristics.
Control charts similar to the hand-drawn ones used earlier to illustrate the
evaluation of processing data are also easily prepared using readily available
software. Figure 16 is an x? chart of tablet assay for active ingredient 2. Note that
minimum maximum specification limits have been included. Figure 17 depicts a
traditional x? control chart for dissolution to which error bars have been added
to denote individual tablet assays for each batch.
Regression analysis requires that a new table be constructed listing the
individual tablet weight (column 1), corresponding assay (column 2), and percentage
of purity of the raw material used to compound the tablet (column 3).
From these data, regression lines and confidence intervals can be plotted to
complement the usual statistics.
Copyright © 2003 Marcel Dekker, Inc.
Figure 15 Drug F: computer-generated scatter plot of ATW vs. assay (AI 1).
Copyright © 2003 Marcel Dekker, Inc.
Figure 16 Drug F: computer-generated x?-control chart of tablet assay (AI 1).
Copyright © 2003 Marcel Dekker, Inc.
Figure 17 Drug F: computer-generated x?-control chart of tablet dissolution (AI 1) with
tablet assay error bars.
Copyright © 2003 Marcel Dekker, Inc.
V. USING VALIDATION EXPERIENCE TO SET PRODUCT
ALERT LIMITS
Experience gained during validation can be used to fine-tune the process for
greater reliability. Several examples of changes being recommended based on
study findings may be found in the section of this chapter devoted to evaluation
of process data. Another application of the information gathered during validation
is in setting alert limits to be incorporated into the mechanism for product
release. The alert limits would be the control limits (UCL and LCL) calculated
as part of the review process for each analytical test; they could be made part
of the written specifications for product release.
The recommendation to use control limits calculated as part of validation
as alert limits is based on the expectation that test results from future production
should normally fall within these limits. Indeed, this is the essence of retrospective
validation. Furthermore, for a stable, centered process the control limits
would fall within the release specification for the test. Exceeding an alert limit
therefore would not necessarily delay product release but could precipitate an
investigation into the cause.
Requiring quality control to use validation experience to release product
achieves two objectives: it monitors conclusions reached during validation for
ongoing reliability and identifies a trend early before a rejection occurs. For
quality control laboratories using a laboratory information management system
(LIMS), routine performance of test result-alert limit comparisons can be automated.
Where such a system is not available, manually recorded test results
could be transferred to a stand-alone computer for trend analysis. An x? plot
depicting the process in relation to the alert and specification limits should be
considered for monitoring trends. See Figure 18 for an example of such a plot.
VI. RELIABILITY OF THE VALIDATED PROCESS
Once the process has been validated, controls must be put into place to make
certain that operations continue to be performed as originally described. It is unreasonable
to assume that machines, instruments, plant services, and personnel will
remain static indefinitely. The FDA recognized the need for revalidation when it
issued the process validation guidelines [1]. A number of resources are available
to monitor for process drift. The quality assurance department can perform periodic
audits of manufacturing and laboratory practices against official procedures, review
equipment maintenance records including calibration history, and examine personnel
training programs. Any departures from original assumptions must be brought
to the attention of the validation team for evaluation of their impact on the process.
The CGMPs require the manufacturer of a product to conduct an annual
review of written records to evaluate product quality [6]. A number of authors
Copyright © 2003 Marcel Dekker, Inc.
Figure 18 Computer-generated x?-control chart showing relationship of historical control
limits (UCL and LCL) and quality control release specifications.
have suggested that when done properly the review can highlight trends that
might otherwise go unnoticed. Lee discusses how analytical and production data,
as well as product complaint experience, can be arranged or collated for this
purpose [19]. The annual review would be an expedient means of monitoring
the conclusions reached during validation.
When planned changes are made to the process, equipment, or immediate
operating environment, the validation team should carefully assess the nature of
the change for its impact on different aspects of the process. It may not be
necessary to revalidate the entire process in cases in which the change can be
shown to be isolated [1]. There may be an opportunity to supplement the historical
experience with a prospective study specific to the planned change. To ensure
that this review occurs, a formal change control system must be in place.
It would also be appropriate to have in place a written plan describing the
company functions that have responsibility for monitoring the process.
VII. SELECTION AND EVALUATION OF PACKAGING DATA
To this point retrospective validation has been discussed in the context of dosage
form manufacture. Some of the same concepts may be applied to validating a
packaging operation. Consider the following. Packaging lines are typically controlled
by making spot observations to confirm machinery performance and
Copyright © 2003 Marcel Dekker, Inc.
component usage. The frequency of the inspections and the number of samples
examined during each cycle are normally defined in a written procedure. Furthermore,
the results of each monitor are generally documented in an inspection
report, which becomes part of the packaging record for that lot of product. Also
available from the packaging record is the number of units produced, thus the
information needed to allow inferences about the reliability of a particular operation
is readily accessible.
If we can show that over an extended period of time an operation had a
certain reliability, it is not unreasonable to expect the same level of performance
for the future as long as the equipment is reasonably maintained. Conversely,
any conclusion reached by such a study would be invalidated by substantial
change to the equipment or its method of operation.
How many packaging runs must be examined to draw a sound conclusion
about the reliability of the operation? Unfortunately, no one answer is appropriate
for every situation, but there are some rules that will aid the decision
process. The sample size should be large enough to capture all variables normally
experienced; for instance, routine machine problems, shift and personnel
changes, component vendor differences, and seasonal conditions. Furthermore,
the sample must be of sufficient size to provide a high degree of confidence in
the conclusion. Ten thousand observations made over 6 to 12 months of continuous
production generally satisfy these requirements. For high-speed, multipleshift
operations the 10,000-observation figure is likely to be reached well before
sufficient time has elapsed to include all avenues of variability. In these cases,
time rather than units produced should be the first consideration.
To validate an aspect of the packaging operation retrospectively the following
information must be tabulated:
1. The total number of observations made for the quality attribute under
review
2. The total number of nonconformances detected by the inspection process
Figure 19 summarizes the retrospective validation strategy for a packaging
operation. It also takes into consideration an opportunity for process improvement.
For example, we may learn from the study that a particular operation has a defect
rate that in our judgment is unreasonably high. The effectiveness of remedial action
could be evaluated after a suitable period of time has elapsed by repeating that
phase of the validation study. In addition, the information provided by the study
about machine and operator dependability permits informed replies to inquiries by
customers or the FDA about alleged package defects.
A. Sources of Historical Information
A specific example can serve to illustrate how validation may be accomplished.
A typical high-speed packaging line for solid dosage form products consists of
Copyright © 2003 Marcel Dekker, Inc.
Figure 19 Packaging operation validation strategy.
Copyright © 2003 Marcel Dekker, Inc.
several pieces of specialized machinery, usually in series, connected by a moving
belt (see Fig. 20). When the line is operational, there is a roving inspection
designed to evaluate the performance of each piece of equipment. For example,
at the labeler the inspector would be asked to confirm that the serial number on
the label matches the work order, that the correct lot number and expiration date
appear on the label, and that the label is properly adhered to the bottle. The
outcome of each inspection is recorded. In the event nonconformance is observed,
packaging supervision is notified. Remedial action may take the form
of a machine adjustment and/or isolation and removal of nonconforming production.
These roving inspections have the effect of limiting the number of defectives
that reach the finished goods stage.
In addition to the roving inspection, a finished piece inspection is performed
each half hr; that is, the inspector randomly selects for examination one
finished unit from the end of the line. In our example, the finished unit is a
unitized bundle of 12 bottles of 100 tablets each. Each finished piece is torn
down into its component parts, which are examined for specific attributes and
conformance to the work order. Table 12 summarizes the tests made by the
inspector, as well as the number of pieces examined at each half-hr interval.
When nonconformance is detected, a notation is made in the inspection record.
With 13 finished product audits performed on each shift, a considerable pool of
information is readily amassed.
Figure 20 Typical layout for high-speed solid dosage form packaging line.
Copyright © 2003 Marcel Dekker, Inc.
Table 12 Finished Product Audit: Package Attributes
and Number Examined
Number examined
Attribute Each audit Each shift Each year
Intact bundle 1 13 1,300
Carton 12 156 15,600
Outsert 12 156 15,600
Bottle 12 156 15,600
Label 12 156 15,600
Lot number
Expiration date
Adhesion
Cap 12 156 15,600
Seal
Tablet counta 4 52 5,200
aTablet count is performed on only four bottles. The annual figure is
based on 100 shifts.
Because we are interested in line machinery and package attributes and
not the drug product being packaged, inspection results for all 100-tablet bottle
runs may be pooled. One could even argue convincingly that the type and number
of doses in the bottle are of no import as long as the line configuration
remains constant. In any event, the pooling of production volume as well as
inspectional observations substantially accelerates data accumulation. This may
be an important consideration in cases in which a particular packaging line is
used for multiple products and sizes.
The line to be studied runs 100 shifts per annum of a particular package
size at the rate of 50,000 bottles per shift; thus, in 1 year 5 million bottles
are produced. During the same period, between 1300 and 15,600 inspectional
observations are made, depending on the attribute (Table 12).
B. Estimating Outgoing Product Quality
The remaining task is to count the number of defects for each attribute as reported
by the inspector during the course of the year following the finished
piece inspection. This task is more time-consuming than difficult, assuming line
inspection documents are well organized. The outcome is reported in Table 13.
With this information available, the maximum fraction defective at a preselected
Copyright © 2003 Marcel Dekker, Inc.
confidence level may easily be estimated. The figures in Table 13 are derived
from the Poisson approximation rather than the normal approximation to the
binomial, which is adequate for this purpose [20].
According to Table 13, the cap was present for each bottle sampled; however,
the lip seal was not fully adhered in 16 instances. The proportion of defectives
in the samples is 16/15,600 or 0.001 (0.1% or 1/1000). The maximum
fraction defective for an incomplete lip seal in the population (production lots)
is 0.0018 at the 99% confidence level. Stated another way, there is 99% assurance
that the number of bottles with an incompletely adhered seal will not exceed
two units for every 1000 produced. The value has been calculated for the
other quality attributes to illustrate the impact of the sample size and the different
levels of machine performance on lot defectives.
Calculating the maximum fraction defective for important package attributes
provides a clear picture of the quality of goods sent to the customer as
well as machine capability. If the defect rate is uncomfortably high, an investigation
can be made to identify the cause. Possibly the solution is to modify a
practice or replace a particular item of equipment.
VIII. CONCLUSION
Under certain conditions, a firm may rely on existing production, quality control,
and facilities maintenance information, and consumer input to validate
retrospectively the processes of marketed products. The end result of this effort
Table 13 Inspectional Results and Fraction Defective
Maximum fraction
Number of Number of defective at 99%
Attribute samples examined observed defects confidence limit
Intact bundle 1,300 11 16.5/1000
Carton 15,600 0 0.3/1000
Outsert 15,600 7 1.0/1000
Bottle 15,600 0 0.3/1000
Label 15,600 0 0.3/1000
Lot number 1 0.4/1000
Expiration date 2 0.511000
Adhesion 5 0.8/1000
Cap 15,600 0 0.3/1000
Seal 16 1.8/1000
Tablet count 5,200 3 1.9/1000
Copyright © 2003 Marcel Dekker, Inc.
is the ability to predict with a degree of confidence the quality of subsequent
batches. Furthermore, familiarity with the product acquired through such indepth
study can lead to process improvement, which in turn enhances overall
control. The knowledge acquired and data amassed during retrospective process
validation provide a performance profile against which daily release testing can
be compared, to say nothing of their value as a guide when resolving production
and control problems. Process validation is a CGMP requirement, and therefore
an area of interest to the FDA. The program just discussed is one approach to
satisfying this requirement. The chapter also extends the concept of using historical
data to predict future performance of packaging operations.
REFERENCES
1. Food and Drug Administration. Guidelines on General Principles of Process Validation.
Rockville, MD: Division of Manufacturing and Product Quality (HFN-320),
Office of Compliance, Center for Drugs and Biologics (May 1987).
2. Brands of the century. Med Ad News 54–59 (Jan. 2000).
3. Ellsworth, D. FDA Field Report. NDMA Manufacturing Controls Seminar, Philadelphia,
Oct. 8–9, 1998.
4. Schilling, E. Acceptance Sampling in Quality Control. 10th ed. New York: Marcel
Dekker, p. 7 (1982).
5. Estes, G. K., Luttsell, G. H. An approach to process validation in a multiproduct
pharmaceutical plant. Pharm Tech 76–77 (April 1983).
6. Food and Drug Administration Current Good Manufacturing Practices in Manufacture,
Processing, Packaging and Holding of Human and Veterinary Drugs. Federal
Register, vol. 43, no. 190, U.S. Government Printing Office, Washington, D.C.
(Sept. 1978).
7. Avallone, H. E. Retrospective validation. NAPM Meeting, Port Chester, NY, Sept.
1983.
8. Sadek, H. M. Considerations for achieving content uniformity in solid/solid blending.
Pharm Mfg 18–21 (March 1985).
9. Western Electric Company. Statistical Quality Control Handbook. 6th ed. Easton,
PA: Mack (1982).
10. Food and Drug Administration. Guidance for Industry, ANDAs: Blend Uniformity
Analysis. Rockville, MD: Center for Drug Evaluation and Research (Aug. 1999).
11. Food and Drug Administration. Guide to Inspection of Oral Solid Dosage Forms:
Pre/Post Approval Issues for Development and Validation. Rockville, MD: Office
of Compliance, Center for Drugs and Biologics (Jan. 1994).
12. Johanson, J. R. Predicting segregation of bimodal particle mixtures using the flow
properties of bulk solids. Pharm Tech 46–57 (May 1996).
13. Juran, J. M., Godfrey, B., eds. Juran’s Quality Handbook. 5th ed. New York: Mc-
Graw-Hill, Sec. 44 (1999).
14. Kieffer, R., Torbeck, L. Validation and process capability. Pharm Tech 66–76
(June 1998).
Copyright © 2003 Marcel Dekker, Inc.
15. Hwang, R., Hwang, Y., Peck, G. R. Evaluation of blend sampling errors: A statistical
approach. Pharm Tech 56–66 (June 1999).
16. Berry, I. R. Process validation for soft gelatin capsules. Drug Cos Ind 26–30 (April
1984).
17. 1999 statistical process control software buyers guide. Qual Digest 19(12): 51–64
(1999).
18. James, P. D., Polhemus, N. W. Graphical methods for quality achievement. ASQC
Quality Control Congress, San Francisco, 1990.
19. Lee, J. Product annual review. Pharm Tech 86–92 (April 1990).
20. Pearson, E. S., Hartley, H. O. Biometrika Tables for Statisticians. vol. 1, Table 40.
London: Cambridge University Press (1962).
Copyright © 2003 Marcel Dekker, Inc.
4
Sterilization Validation
Michael J. Akers
Baxter Pharmaceutical Solutions, Bloomington, Indiana, U.S.A.
Neil R. Anderson
Eli Lilly and Company, Indianapolis, Indiana, U.S.A.
I. INTRODUCTION
Sterile products have several unique dosage form properties, such as freedom
from micro-organisms, freedom from pyrogens, freedom from particulates, and
extremely high standards of purity and quality; however, the ultimate goal in
the manufacture of a sterile product is absolute absence of microbial contamination.
The emphasis of this chapter will be the validation of the sterilization
processes responsible for achieving this goal.
Unlike many dosage form specifications, the sterility specification is an
absolute value. A product is either sterile or nonsterile. Historically, judgment
of sterility has relied on an official compendial sterility test; however, endproduct
sterility testing suffers from a myriad of limitations [1–4]. The most
obvious limitation is the nature of the sterility test. It is a destructive test; thus,
it depends on the statistical selection of a random sample of the whole lot.
Uncertainty will always exist as to whether or not the sample unequivocally
represents the whole. If it were known that one unit out of 1000 units was
contaminated (i.e., contamination rate = 0.1%) and 20 units were randomly sampled
out of those 1000 units, the probability of that one contaminated unit being
included in those 20 samples is 0.02 [5]. In other words, the chances are only
2% that the contaminated unit would be selected as part of the 20 representative
samples of the whole 1000-unit lot.
Even if the contaminated unit were one of the 20 samples selected for the
sterility test, the possibility still exists that the sterility test would fail to detect
Copyright © 2003 Marcel Dekker, Inc.
the contamination. The microbial contaminant might be at too low a concentration
to be detectable during the incubation period or might not grow rapidly
enough or at all because of media and incubation insufficiencies.
If microbial growth is detected in a sterility test, this may reflect a falsepositive
reading because of the problem of accidental contamination of the culture
media while performing the sterility test. The problem of accidental contamination
is a serious yet unavoidable limitation of the sterility test.
The Food and Drug Administration (FDA) published guidelines pertaining
to general principles of process validation [6]. General concepts and key elements
of process validation considered acceptable by the FDA were outlined. A
major point stressed in the guidelines was the insufficiency of relying solely on
end-product sterility testing alone in ascertaining the sterility of a parenteral of
a sterile product lot. Greater significance should be placed on process validation
of all systems involved in producing the final product.
These major limitations demonstrate that reliance on end-product sterility
testing alone in ascertaining the sterility of a parenteral product may lead to
erroneous results. One purpose of validation in the manufacture of sterile products
is to minimize this reliance on end-product testing. Three principles are
involved in the validation process for sterile product.
1. To build sterility into a product
2. To demonstrate to a certain maximum level of probability that the
processing and sterilization methods have established sterility to all
units of a product batch
3. To provide greater assurance and support of the results of the endproduct
sterility test
Validation of sterile products in the context of this chapter will refer to the
confirmation that a product has been exposed to the appropriate manufacturing
processes and especially to the appropriate sterilization method yielding a batch
of product having a known degree of nonsterility.
II. PROCESS OF MICROBIAL DESTRUCTION
Regardless of the type of lethality induced by a sterilization process—whether
it be heat, chemical, or radiation—micro-organisms, upon exposure to adequate
levels of such treatments, will die according to a logarithmic relationship between
the concentration or population of living cells and the time exposure or
radiation dose to the treatment. This relationship between the microbial population
and time may be linear or nonlinear, as seen in Figure 1. The D value, or
the time or dose required for a one-log reduction in the microbial population,
may be calculated from these plots.
Copyright © 2003 Marcel Dekker, Inc.
Figure 1 Linear (1-A) and nonlinear (1-B) survivor curves.
A. D Value
The D value is a single quantitative expression of the rate of killing of microorganisms.
The D term refers to the decimal point in which microbial death
rates become positive time values by determining the time required to reduce
the microbial population by one decimal point. This is also the time required
for a 90% reduction in the microbial population. Hence, the time or dose it takes
to reduce 1000 microbial cells to 100 cells is the D value. The D value is
important in the validation of sterilization processes for several reasons.
1. It is a specific kinetic expression for each micro-organism in a specific
environment subjected to a specific sterilization agent or condition.
In other words, the D value will be affected by
a. The type of microorganism used as the biological indicator.*
*Biological indicators (BIs) are live spore forms of micro-organisms known to be the most resistant
living organisms to the lethal effects of the particular sterilization process. For steam sterilization,
the most resistant microorganism is Bacillus stearothermophilus. Spore forms of this micro-organism
are used as the BI for steam sterilization validation. BIs for other sterilization processes are
identified in the USP24/NF19, pp. 231–234.
Copyright © 2003 Marcel Dekker, Inc.
b. The formulation components and characteristics (e.g., pH).
c. The surface on which the micro-organism is exposed (glass, steel,
plastic, rubber, in solution, dry powder, etc.).
d. The temperature, gas concentration, or radiation dose of the particular
sterilization process.*
2. Knowledge of the D value at different temperatures in heat sterilization
is necessary for the calculation of the Z value. (See p. 87.)
3. The D value is used in the calculation of the biological F value. (See
p. 87.)
4. Extrapolation of the D value from large microbial population values
to fractional (e.g., 10?x) values predicts the number of log reductions
a given exposure period will produce.
D values are determined experimentally by either of two methods, the
survivor-curve method or the fraction-negative method [7,8]. The survivor-curve
method is based on plotting the log number of surviving organisms versus an
independent variable such as time, gas concentration, or radiation dose. The
fraction-negative method uses replicate samples containing identical spore populations
treated in an identical manner and determining the number (fraction) of
samples still showing microbial growth after treatment and incubation. Fractionnegative
data are used primarily for determining D values of micro-organisms
exposed to thermal destruction processes. The following discussion concentrates
on D values calculated by the survivor-curve method.
Data obtained by the survivor-curve method are plotted semilogarithmically.
Data points are connected by least-squares analysis. In most cases the
equation used is the first-order death rate equation,
log N = a + bt (1)
where N is the number of surviving organisms of time t, a is the Y intercept,
and b is the slope of the line as determined by linear regression. The D value is
the reciprocal of the linear slope,
D = 1
b
(2)
Many micro-organisms produce nonlinear survivor curves, such as 1-B in Figure
1. The cause of nonlinear survivor curves has been explained by several theories,
such as the multiple critical sites theory [9], experimental artifacts [10],
and the heterogeneity of spore heat resistance [11]. Mathematical models for
concave survivor curves have been developed by Han et al. [12]. They are quite
*Therefore, stating that the D value = 1 minute, for example, is meaningless unless all of the above
factors have been identified.
Copyright © 2003 Marcel Dekker, Inc.
complicated. For example, the D value for a nonlinear survivor curve can be
calculated from the following equation:
D =
1
log C0
?
[1 ? ?]t ? [?Be(?t/B?1)]
log Ct
(3)
where C0 and Ct are initial and final concentrations of spores, t is the time
exposure at constant temperature, ? is a constant related to the secondary slope
of the concave curve, and B is a parameter obtained from the Y intercept extrapolated
from the second slope. It is far easier, while less accurate, to apply linear
regression to fit the survivor curve data statistically to a straight line and calculate
the D value and level of confidence in that calculated value from the slope
of the linear line.
A product being validated for sterility should be associated with a characteristic
D value for the micro-organism either most likely to contaminate the
product or most resistant to the process used to sterilize the product. The employment
of BIs in the validation of sterile products has the purpose of assuring
that the sterilization process that causes a multiple log reduction in the BI population
in the product will most certainly be sufficient in destroying all other
possible viable contaminants.
B. Z and F Values
These terms heretofore have been applied exclusively in the validation of heatsterilization
processes. The Z value is the reciprocal of the slope resulting from
the plot of the logarithm of the D value versus the temperature at which the D
value was obtained. The Z value may be simplified as the temperature required
for a one-log reduction in the D value:
Z = T2 ? T1
log D1 ? log D2
(4)
Figure 2 presents thermal resistance plot for a Z value of 10°C, the accepted
standard for steam sterilization of B. stearothermophilus spores, and for a Z
value of 20°C, the proposed standard [13] for dry-heat sterilization of B. subtilis
spores. These plots are important because one can determine the D value of the
indicator micro-organism at any temperature of interest. In addition, the magnitude
of the slope indicates the relative degree of lethality as temperature is
increased or decreased.
Mathematical derivation of the Z value equation permits the calculation
of a single quantitative expression for effective time exposure at the desired
temperature for sterilization. The F value measures equivalent time, not clock
time, that a monitored article is exposed to the desired temperature (e.g., 121°C).
F values are calculated from the following equation:
Copyright © 2003 Marcel Dekker, Inc.
Figure2 Thermal resistance plots of log D versus temperature, showing slopes equivalent
to Z = 10°C and Z = 20°C.
F = ?t ? 10T?T0)/Z (5)
where ?t is the time interval for the measurement of product temperature T and
T0 is the reference temperature (e.g., T0 = 121°C for steam sterilization). The F
value is shown in Figure 3. Another equation for the F value as depicted in
Figure 3 is given in the following expression:
F = ?t2
t1
Ldt (6)
where L = 10(T?T0)/Z, which is the lethality constant integrated over time limits
between time 1 and time 2. Integrating Eq. (6) between two time points will
yield the area under the 10(T?T0)/Z versus time curve, as seen in Figure 3.
The more familiar F0 equation is specific for a Z value of 10°C and a T0
value of 121°C.
F0 = ?t ? 10(T?121)/10 (7)
An example of a manual calculation of F0 value is presented in Table 1.
Copyright © 2003 Marcel Dekker, Inc.
Figure 3 Plot showing the difference between chamber temperature versus time
( ) and lethal rate in the product versus time (




). F is the area under the dottedline
curve.
The F0 value is mentioned both in the USP and in the Current Good
Manufacturing Practices (CGMPs) for large volume parenterals (LVPs). Both
sources indicate that the steam sterilization process must be sufficient to produce
an F0 value of at least 8 min. This means that the coolest location in the sterilizer
loading configuration must be exposed to an equivalent time of at least 8 min
of exposure to a temperature of at least 121°C. Unless the D value is known,
however, the number of log reductions in the microbial indicator population will
not be known. This is why knowledge of the D value is of extreme importance
in determining the log reduction in the microbial bioburden.
The equation used for determining the microbial log reduction value is
derived as follows:
Dt = t
log A ? log B
(8)
where t is the heating time at a specific temperature, A the initial number of
micro-organisms (bioburden or microbial load), and B the number of surviving
micro-organisms after heating time t. By defining t in Eq. (8) as the equivalent
time exposure to a given temperature T, Eq. (8) then may be expressed as
DT = FT
log A ? log B
(9)
When Eq. (9) is rearranged to solve for the microbial reduction value
Copyright © 2003 Marcel Dekker, Inc.
Table 1 A Manual Calculation of F0 Value
Sterilization Product
time (min) temperature (°C) 10(T-121)/10
5 100 0.008
6 103 0.016
7 106 0.032
8 109 0.063
9 112 0.126
10 115 0.251
11 118 0.501
12 121 1.000
13 121 1.000
14 121 1.000
15 118 0.501
16 115 0.251
17 112 0.126
18 109 0.063
19 106 0.032
20 103 0.016
21 100 0.008
F0 = 5.000 mina
aF0 = ?t (? of lethal rates) = 1 ? 4.994 = 5.0 min; ?t is the
time interval between successive temperature measurements.
log A ? log B = Yn = FT
DT
(10)
As an example, if FT = 8 min and DT = 1 min, the microbial reduction value Yn =
8, or the process has been sufficient to produce 8 log reductions in the microbial
population having a D value of 1 min at the specified temperature T.
C. Probability of Nonsterility
Pflug [14] suggested that the term probability of a nonsterile unit be adopted to
define products free of microbial contamination. This term mathematically is B
in Eq. (10). Thus, solving for B
B = antilog 
log A ? FT
DT (11)
Copyright © 2003 Marcel Dekker, Inc.
The expression 10?6, commonly used in sterilization validation, is the B term in
Eq. (11). What this means is that after an equivalent time-exposure period of FT
units, the microbial population having an initial value of A has been reduced to
a final B value of 10?6. Statistically, this exponential term signifies that one out
of 1 million units of product theoretically is nonsterile after sterilization exposure
of FT units. For example, if 106 micro-organisms having a D value of 1
min at 121°C are placed in a container and the container exposed to 121°C for
an equivalent time of 12 min
B = antilog 
log 106 ?
12 min
1min  = 10?6 (12)
Probability of nonsterility may be extrapolated from the D value slope when
plotting the log of the microbial population versus time (equivalent time at a
specific temperature), as shown in Figure 4.
Figure 4 Survivor curves showing the effect of decreasing the microbial load (A) from
106 to 102 on the time required to achieve a probability of nonsterility (B) of 10?6.
Copyright © 2003 Marcel Dekker, Inc.
Manipulation of the A, FT, and DT values in Eq. (11) will naturally produce
different values of B. Accordingly, if it is desirable that B be as low as possible,
this may be accomplished in one of three ways: (1) reducing the bioburden A
of the bulk product, (2) increasing the equivalent exposure time FT, or (3) employing
a micro-organism with a lower D value at the specified temperature.
Since option 3 most likely is impossible, as the most resistant micro-organisms
of a fixed D value must be used in sterilizer validation, one must either employ
techniques to assure the lowest possible measurable microbial bioburden prior
to sterilization or simply increase the sterilization cycle time.
III. BASIC PRINCIPLES IN THE VALIDATION
OF STERILE PRODUCTS
The key to successful validation in sterile product processing, as in any of type
of process validation, is being systematic in the theoretical approaches to validation,
the performance of the actual validation experiments, and the analysis and
documentation of the validation data.
A. Theoretical Approaches
Generally, five basic steps are necessary to validate any manufacturing process
[15].
1. Written documentation
2. Manufacturing parameters
3. Testing parameters
4. In-process controls
5. Final product testing
In sterile product manufacturing, five major steps are involved in approaching
the validation of a sterile process. These are outlined below using thermal sterilization
as the example process.
1. Select or define the desired attributes of the product. Example: The
product will be sterile.
2. Determine specifications for the desired attributes. Example: The
product will be sterilized by a sterilization process sufficient to produce
a probability of nonsterility of one out of 1 million containers
(10?6).
3. Select the appropriate processes and equipment. Example: Use microbial
kinetic equations such as Eq. (11) to determine the probability
of nonsterility. Select cleaning equipment and container component
Copyright © 2003 Marcel Dekker, Inc.
procedures designed and validated to reduce the product bioburden to
the lowest practical level. Select an autoclave that can be validated in
terms of correct operation of all mechanical controls. Use the appropriate
types of thermocouples, thermal sensing devices, biological indicators,
integrated chemical indicators, and culture media to conduct
the validation tests.
4. Develop and conduct tests that evaluate and monitor the processes,
equipment, and personnel.
Examples:
a. Determine microbial load counts prior to container filling.
b. Determine D and Z values of biological indicator organism.
c. Perform heat distribution studies of empty and loaded autoclave.
d. Perform heat penetration studies of product at various locations
in the batch.
5. Examine the test procedures themselves to ensure their accuracy and
reliability.
Examples:
a. Accuracy of thermocouples as a function of variances in time and
temperature.
b. Repeatability of the autoclave cycle in terms of temperature and
F value consistency.
c. A challenge of the sterilization cycle with varying levels of bioindicator
organisms.
d. Reliability of cleaning processes to produce consistent low-level
product bioburdens.
Each validation process should have a documented protocol of the steps
to follow and the data to collect during the experimentation. As an example,
App. I presents a protocol for the validation of a steam sterilization process.
Upon completion of the experimental phase of validation, the data are
compiled and evaluated by qualified scientific personnel. The results may be
summarized on a summary sheet, an example of which is shown in Table 2.
Once a process has been validated, it must be controlled to assure that the
process consistently produces a product within the specifications established by
the validation studies. As shown in Table 2, documentation should present original
validation records, a schedule of revalidation dates, and data from the revalidation
studies. The interval between validation studies strictly depends on the
judgment of the validation team based on the experience and history of the
consistency of the process.
Table 3 lists the sterilization methods used for sterile products. There are
five basic methods—heat, gas, radiation, light, and filtration. The first four
methods destroy microbial life, while filtration removes micro-organisms. Vali-
Copyright © 2003 Marcel Dekker, Inc.
Table 2 Steam Sterilization Process Summary Sheet
Autoclave identification number or letter: P6037
Location: building 22, floor 1
Tag No.: 896101
Validation date: 10-14-99
Revalidation date: 4-14-00
Description of process validated: load containing filling
equipment and accessories not to exceed 102 kg
Temperature set point for validation: 121.0°C
Temperature range for validation: ±0.5°C
Cycle validated: 35 min
Validation records stored in archives: A105-11
Revalidation records stored in archives: C314-70
dation approaches and procedures used for most of these methods will be addressed
in the remainder of this chapter. Gaseous validation and radiation validation
approaches will be focused on ethylene oxide and gamma radiation,
respectively. The other gaseous and radiation methods, however, generally will
follow the same principles as those discussed for ethylene oxide and gamma
Table 3 Methods of Sterilization of Sterile Products
Heat
1. Moist heat (steam) = saturated steam under pressure =
autoclave
2. Dry heat = oven or tunnel
Gas
1. Ethylene oxide
2. Peracetic acid
3. Vapor phase hydrogen peroxide
4. Chlorine dioxide
Radiation
1. Gamma
2. Beta
3. Ultraviolet
4. Microwave
Light
1. PureBright
Filtration
Copyright © 2003 Marcel Dekker, Inc.
radiation. Some extra coverage will be given to vapor phase hydrogen peroxide
because of its increased application, particularly in the sterilization of barrier
isolators.
IV. VALIDATION OF STEAM STERILIZATION CYCLES
A. General Considerations
The literature contains more information on steam sterilization validation than
any other process in the sterile product area. One reason was the publication of
the proposed CGMPs for LVPs in June 1976. Actually, the FDA had been
surveying the LVP industry long before the proposed CGMPs for LVP regulations
were published. One of the major areas of concern was sterility and the
heat sterilization processes for achieving sterility. Thus, at least three sections of
the proposed CGMPs for LVPs contain statements related to steam sterilization
validation. Although these regulations have not become officially and legally
valid, they are taken seriously by the parenteral industry. Table 4 summarizes
CGMP-LVP statements pertaining to steam sterilization validation.
The key expression used in steam sterilization validation is F0. Interestingly,
despite the familiarity of this term, it is still misunderstood or misused in
the parenteral industry. The main purpose of the F0 value is to express in a
single quantitative term the equivalent time at which a microbial population
having a Z value of 10°C has resided at a temperature of 121.1°C. The time
units here are not clock time units; rather, F0 time is a complete summary of
the time the indicator organism spent during the entire cycle at a temperature of
exactly 121.1°C plus a fraction of the times spent at temperatures below
121.1°C, in addition to a multiple of the times spent at temperatures greater than
121.1°C. F0 is a summation term, as exemplified in Figure 3 and Table 1. F0 is
a time value that is referenced to 121.1°C. It includes heat effects on microorganisms
during the heating and cooling phases of the cycle, taking into account
that heat effects below 121.1°C are not as powerful in destroying microbial
life as the effect found at 121.1°C.
F0 values may be calculated in several ways. The basic way is by manually
recording the temperature of the monitored product at specific time intervals,
substituting the recorded temperature for T in Eq. (7), solving the exponential
part of the equation for all temperatures recorded, and then multiplying by ?t.
This was done in Table 1. Alternatively, and more expediently, a computer
program can integrate the temperature and time data to obtain the F0 value.
This approach is now widely used because of the availability of programmable
multipoint recorders that record temperature and solve the F0 equation on an
accumulative basis.
Copyright © 2003 Marcel Dekker, Inc.
Table 4 Statements Concerning Sterilization Cycle Design and Validation in the
Proposed Good Manufacturing Procedures for LVPs
Section 212.240
Procedure for steam sterilization must be sufficient to deliver an F0 of 8 or more
Section 212.243
Testing of the sterilization processes requires:
1. A maximum microbial count and a maximum microbial heat resistance for filled
containers prior to sterilization.
2. Heat distribution studies for each sterilizer, each loading configuration, every container
size, using a minimum of 10 thermocouples.
3. Heat penetration studies using product of similar viscosity as that packaged in container
studied. Locate slowest heating point in the container. Use 10 or more containers,
each with a suitable biological indicator and submerged thermocouple. F0 value
is determined beginning when the sterilizer environment has established itself as
shown by reproducible heat distribution studies and specific sterilizer temperature
has been achieved, and ending when cooling has been initiated.
Section 212.244
Statements on sterilization process design
1. Procedures required to establish uniform heat distribution in the sterilizer vessel.
Temperatures must be held at ±0.5°C from the time the product achieves process
temperature until the heating portion completed.
2. Verify uniformity of heat distribution for each loading pattern.
3. Temperature of the product and the sterilizer must not fall below the minimum that
has been established for the prescribed sterilization process.
4. Establish the time requirement for venting the sterilizer of air.
5. Establish the product come-up time to the desired temperature.
6. Establish the cooling time.
F0 values may be solved using the biological approach [i.e., Eq. (9)]. The
approach is used when D121 and A are accurately known and a desired level of
survivor probability (B) is sought. In this case, Eq. (9) is rearranged as
F0 = D121(log A ? log B)
For example, if D121 = 1.0 min, A = 106, and B = 10?6, F0 is calculated to be
F0 = 1(log 106 ? log 10?6) = 12 min
Thus, the cycle must be adjusted so that the F0 value calculated by physical
methods (time and temperature data) will be at least 12 min.
Copyright © 2003 Marcel Dekker, Inc.
An approach for solving F0 values involves the use of a chemical indicator,
called Thermalog S,* which is calibrated in terms of F0 units. The device
was described by Witonsky [16] and evaluated by Bunn and Sykes [17]. Thermalog
strips are placed in the containers being steam sterilized. Each strip contains
a chemical sensor that responds to increasing saturation steam temperature.
The millimeter distance advanced by the chemical sensor is linearly related to
the F0 value (T0 = 121°C, Z = 10°C). The advantages of using this device lie in
its replacing biological indicators in the validation and monitoring of steam
sterilization cycles and its ability to assess F0 in any part of the sterilizer load,
however inaccessible to conventional thermocouple monitoring devices. The
main disadvantage is the paucity of available data proving the sensitivity and
reliability of the chemical indicator system.
With the main emphasis being the validation of a steam sterilization cycle
based on the achievement of a certain reproducible F0 value at the coolest part
of the full batch load, procedures for validation of a steam sterilization process
will now be discussed.
B. Qualification and Calibration
1. Mechanically Checking, Upgrading, and Qualifying
the Sterilizer Unit
The functional parts of an autoclave are shown in Figure 5. The main concern
with steam sterilization is the complete removal of air from the chamber and
replacement with saturated steam. Older autoclaves relied on gravity displacement.
Modern autoclaves use cycles of vacuum and steam pulses to increase the
efficiency of air removal. Autoclaves can also involve air–steam mixtures for
sterilizing flexible packaging systems and syringes. Whatever autoclave system
is used, the unit must be installed properly and all operations qualified through
installation qualification and operation qualification (IQ/OQ). Utilities servicing
the autoclave must be checked for quality, dependability, proper installation,
and lack of contamination. The major utility of concern here is steam. All equipment
used in studying the steam sterilizer, such as temperature and pressure instrumentation,
must be calibrated.
2. Selection and Calibration of Thermocouples
Thermocouples obviously must be sufficiently durable for repeated use as temperature
indicators in steam sterilization validation and monitoring. Copperconstantan
wires coated with Teflon are a popular choice as thermocouple monitors,
although several other types are available.
*Bio Medical Sciences, Fairfield, NJ.
Copyright © 2003 Marcel Dekker, Inc.
Figure5 The functional parts of a modern autoclave. (Courtesy of American Sterilizer
Company, Erie, Pennsylvania.)
Accuracy of thermocouples should be ±0.5°C. Temperature accuracy is
especially important in steam sterilization validation because an error of just
0.1°C in temperature measured by a faulty thermocouple will produce a 2.3%
error in the calculated F0 value. Thermocouple accuracy is determined using
National Bureau of Standards (NBS) traceable constant temperature calibration
instruments such as those shown in Figure 6. Thermocouples should be calibrated
before and after a validation experiment at two temperatures: 0°C and
125°C. The newer temperature-recording devices are capable of automatically
correcting temperature or slight errors in the thermocouple calibration. Any thermocouple
that senses a temperature of more than 0.5°C away from the calibration
temperature bath should be discarded. Stricter limits (i.e., <0.5°C) may
be imposed according to the user’s experience and expectations. Temperature
recorders should be capable of printing temperature data in 0.1°C increments.
Copyright © 2003 Marcel Dekker, Inc.
Figure 6 Modern equipment employed in the calibration of thermocouples used in
sterilizer validation studies. (Courtesy of Kaye Instruments, Inc., 15 De Angelo Drive,
Bedford, Massachusetts.)
3. Selection and Calibration of BI
The organism most resistant to steam heat is the bacterial spore former B. stearothermophilus.
Other indicator organisms have been employed, but B. stearothermophilus
spores are by far the most commonly used BIs in validating
steam sterilization cycles.
Since the main purpose of BIs is to assure that a minimum F0 value has
been achieved in the coolest location of the autoclave load, the D121 and Z values
of the BI must be accurately known. Whether BIs have been prepared by the
manufacturer or purchased commercially, laboratory D values must be calculated
[18].
Spore strips or spore suspensions are used in the validation studies. The
number of micro-organisms per strip or per ml of suspension must be as accurately
known as the D value.
Copyright © 2003 Marcel Dekker, Inc.
Precautions should be taken to use proper storage conditions for B stearothermophilus
BIs. Storing in the freezer provides a more stable resistance profile
for the shelf life of the indicator [19].
If one knows the D value, the BI concentration or population A and the
desired probability level of nonsterility B, the minimum F0 value that must be
achieved by the sterilization cycle for the particular load can be calculated. For
example, if A = 106 and B = 10?6 and laboratory studies determine the D value
for B. stearothermophilus in the product to be sterilized to be 0.4 min (F0 =
0.4(12) = 4.8 min), a minimum F0 value of 4.8 min should be achieved at the
worst case location during heat-penetration studies. The USP requires a steam
sterilization process to deliver a lethality input of 12D for a typical “overkill”
approach.
C. Heat-Distribution Studies
Heat-distribution studies include two phases: (1) heat distribution in an empty
autoclave chamber and (2) heat distribution in a loaded autoclave chamber. Between
10 and 20 thermocouples should be used per cycle. Thermocouples
should be secured inside the chamber according to a definite arrangement (e.g.,
see Fig. 7); Teflon tape can be used to secure thermocouples. The trips where
Figure 7 Suggested locations for thermocouples on a single shelf for heat-distribution
studies in heat sterilizers.
Copyright © 2003 Marcel Dekker, Inc.
the wires are soldered should not make contact with the autoclave interior walls
or any metal surface. One thermocouple each should remain in an ice bath and
high-temperature oil bath during each cycle for reference when the temperaturemonitoring
equipment has the capability for electronically compensating each
temperature measurement against an internal reference. Heat-distribution studies
following the initial study may employ fewer thermocouples as the cool spot in
the chamber and in the load is identified. The key is to identify on a reproducible
basis the location of the cool spot and the effect of the load size and/or configuration
on the cool spot location. Most experts suggest the study of the minimum
and maximum load size in the proper configuration in elucidating where the
cool spot is located.
The difference in temperature between the coolest spot and the mean
chamber temperature should be not greater than ±2.5°C [7].* Greater temperature
differences may be indicative of equipment malfunction.
D. Heat-Penetration Studies
This is the most critical component of the entire validation process. The success
of a validated cycle depends on determining the F0 value of the cold spot inside
the commodity located at the cool spot previously determined from heat-distribution
studies. The container cold spot for containers ?100 ml is determined
using container-mapping studies. Thermocouple probes are inserted within a
container and repeat cycles are run to establish the point inside the container
that is coldest most of the time. It is this exact point that is monitored during
heat-penetration studies.
Again, the minimum and maximum loading configurations should be studied.
Thermocouples will be placed both inside and outside the container at the
cool spot location(s), in the steam exhaust line, and in constant-temperature
baths outside the chamber. The F0 value will be calculated based on the temperature
recorded by the thermocouple inside the container at the coolest area of the
load. Upon completion of the cycle, the F0 value will indicate whether the cycle
is adequate or if alterations must be made. Following the attainment of the
desired time–temperature cycle, cycles are repeated until the user is satisfied
with the repeatability aspects of the cycle validation process. Statistical analysis
of the F0 values achieved at each repeated cycle may be conducted to verify the
consistency of the process and the confidence limits for achieving the desired
F0 value.
There are three critical times associated with all wet heat sterilization
processes (20).
*In fact, a difference ?1.0°C gives rise to the suspicion of air-stream mixtures in the chamber.
Copyright © 2003 Marcel Dekker, Inc.
1. A minimum F value
2. A design F value
3. A sterilization process time
The minimum F value is based only on microbial spore destruction. It is
believed that F0 = 12 min is a realistic minimum value, since most mesophilic
spore-forming micro-organisms have D values ?0.5 min at 121°C. Even if D121 =
1.0 min, the spore log reduction value according to Eq. (10) would be 12*.
The F value used in the design of a sterile cycle may greatly exceed the
minimum F0 of 12. An F0 = 18 min will provide a 50% safety factor that will
take into account additional time that may be required for steam to penetrate
certain containers in middle or cool locations of the autoclave.
The sterilization process time is determined from the design F value and
the product heat transfer data. The sterilization cycle design must be based on
the heating characteristics of the load and of containers located in the slowest
heating zone of the load. The variation in the rate of heating of the slowest
heating zone must be known, so this variation must be determined under fully
loaded conditions. The effect of load-to-load variation on the time–temperature
profile must also be determined. Then, the statistically worst-case conditions
should be used in the final sterilization process design.
The final step in steam sterilization validation is the establishment of a
monitoring program to ensure that the validated cycle remains essentially unchanged
in the future. Cycle monitoring usually involves the use of thermocouples
to measure heat penetration at the cool spot location and to verify that the
design F0 value has been reached.
Any changes in the load size, load configuration, or container characteristics
(volume, geometry, etc.) must be accompanied by repeat validation studies
to prove that the cool spot location has not changed or, if it has, that it receives
the design F0 time exposure from the sterilization cycle used.
V. VALIDATION OF DRY-HEAT STERILIZATION CYCLES
A. General Considerations
Two types of dry-heat sterilization systems are utilized in the pharmaceutical
industry today. They are the conventional hot air oven and the tunnel system.
The major difference between the two systems, as far as validation is concerned,
is the belt or line speed variable with the tunnel system.
The key to validating a dry-heat sterilizer is to prove its repeatability. This
*A current trend for overkill sterilization validation is to establish the minimum Fo value that will
result in the inactivation of 106 B. stearothermophilus spores then double the dwell time for this Fo
value to provide assurance of overkill.
Copyright © 2003 Marcel Dekker, Inc.
means that the unit can consistently perform under a given set of conditions to
generate materials that are sterile, pyrogen-free, and particulate-free. Repeatability
in dry-heat sterilization obviously involves consistency and reliability in attaining
and maintaining a desired temperature. The desired temperature must be reached
in all areas of the heating chamber. There will always be an area in the chamber
that represents a cold spot; that is, an area that is most difficult to heat up to the
desired temperature. This cold spot must be identified so that validation studies
involving thermocouple monitoring and microbial challenges can be done at this
location. If certain key GMP features of the dry-heat sterilizer are not controlled,
with time the cold spot within the sterilizer will change and the key element of
validation repeatability cannot be achieved. Simmons [21,22] discussed the GMP
features of both the batch oven and tunnel sterilizer that must be controlled before
doing any validation studies. These are listed in Tables 5 and 6. Without control
of these processes features, as Simmons has clearly stated, validating or even
qualifying a dry-heat sterilizer is a total waste of time and money.
As with any sterilization process, the first step in dry-heat sterilizer validation
involves qualification of all the equipment and instrumentation used. This
step includes examination and documentation of all utilities, ductwork, filters,
and control valves or switches for the oven or tunnel unit, and the calibration
of the instrumentation used in validating and monitoring the process. The instruments
used are as follows:
1. Temperature recorders and thermocouples
2. Constant-temperature baths
3. Amp meters
4. Monometers
5. Dioctylphthalate generators
6. Particle counters
7. Velometers
8. Tachometers
Table 5 Key Process Features to Control Prior to
Validating Dry-Heat Sterilizers
Batch (oven) Tunnel sterilizer
Intake air system Positive pressure to entrance
Exhaust air system Even distribution of heat
Internal air circulation Belt speed recorder
Exhaust HEPA filter HEPA-filtered cooling air
Static pressure gauge Exhaust HEPA filter
Heater current Heater current
Particulate control
Copyright © 2003 Marcel Dekker, Inc.
Table 6 Basic Equipment Performances That Must Be Verified Prior to
Calibration-Validation Studies
Dry heat process
Convection Convection Conduction Radiant
Function batch continuous batch continuous
Electrical logic ? ? ? ?
Cycle set point adjustment ? ? ? ?
Vibration analysis ? ? ? ?
Blower rotation ? ? ? ?
Blower rpm ? ? ? ?
Heater elements ? ? ? ?
Air balance ? ? ? ?
Air balance ability ? ? ? ?
Door interlocks ?
Commodity interlocks ?
Gasket integrity ? ?
HEPA filter integrity ? ? ?
Belt speed ? ?
Heat shields ? ?
Calibration should be conducted on a regular interval basis. Simmons [22] recommends
a regular calibration interval of every 3 months.
Validation studies conducted on dry-heat sterilizers can be divided into two
basic components. One component envelops all the physical elements that must
be qualified, such as temperature control, air particulate levels, and belt speeds.
The other component is the biological constituent, which involves studies that
prove that the process destroys both microbial and pyrogenic contaminants.
B. Batch Oven Validation
1. Air balance determination. In an empty oven, data are obtained on the
flow rates of both intake and exhaust air. Air should be balanced so
that (a) positive pressure is exerted to the nonsterile side when the
door is opened and (b) air velocity across and up and down the opening
of the door is ±50 feet per minute (FPM) of the average velocity
(measured 6 in. from the side wall on the air supply wall).
2. Heat distribution of an empty chamber. Thermocouples should be situated
according to a specific predetermined pattern. Repeatability of
temperature attainment and identification of the cold spot can be
Copyright © 2003 Marcel Dekker, Inc.
achieved if the temperature range is ±15°C at all monitored locations.
Heat-distribution studies can also be conducted as a function of variable
air flow rates through the hood ducts and as a function of the gas
flowrate to the sterilizing burners.Asuggested thermocouple placement
pattern per shelf in an empty oven is presented in Figure 7.
3. Heat-penetration studies. These studies should be designed to determine
the location of the slowest heating point within a commodity at
various locations of a test load in the sterilizer. The test load should
be the maximum size of load anticipated. Thermocouples are placed
in the commodities located in the areas likely to present the greatest
resistance to reaching the desired temperature. Minimum and maximum
temperatures as defined in the process specifications should be
studied. Normally, three replicate cycles are run at each temperature.
The cold spot must not move during the replicate studies. Firm identification
of the most difficult location for heat to penetrate will represent
the area to be used for the biological challenge studies. Other
variations in the cycle affecting heat penetration at the cold spot can be
studied, and these might include (a) test load variations, (b) temperature
set point variations, and (c) variations in the time of exposure.
4. Mechanical repeatability. During all these studies, mechanical repeatability
in terms of air velocity, temperature consistency, and reliability
and sensitivity of all the oven and instrumental controls must be verified.
C. Tunnel Sterilizer Validation
Principles as described above for the physical process validation of batch ovens
apply also in the validation of tunnel sterilizers; however, in addition to the
variables affecting batch oven validation, tunnel sterilizers have an extra variable-
belt speed. This variable can be held constant by maintaining the same belt
speed throughout the validation process and not changing it after validation has
been completed.
1. Air Balance Determination
Proper and even air balance is more critical to a tunnel sterile process than a
batch oven process. Since the items being sterilized are moving, they are exposed
to different air systems (e.g., heating zone and cooling zone). Air flow
must be balanced in order to provide a gradual decrease in air temperature as
items move along the conveyor. In the absence of a critical balance of air dynamics,
either the items will not be cooled sufficiently once they exit the tunnel
or they will be cooled too quickly, causing the glass to shatter and contaminate
the entire tunnel area with particles. In fact, the major problem in validating
Copyright © 2003 Marcel Dekker, Inc.
tunnel sterilizers is the control of particles. Not only are the items exposed to
great extremes in temperature, but also the conveyor belt is a natural source of
particulates because metal is moving against metal.
Adjustments in the air source should be made to obtain a controlled flow
of air within the tunnel and across the entrance and exit openings. Air must be
particulate-free as it enters the tunnel area; therefore, all high efficiency particulate
air (HEPA) filters in the tunnel must be integrity tested and certified prior
to validation studies.
2. Heat-Distribution Studies
Thermocouples used in tunnel sterilizer validation must be sufficiently durable
to withstand the extremely high (?300°C) temperatures in the heating zone area
of the tunnel. Heat-distribution studies should determine where the cold spots
are located as a function of the width of the belt and height of the tunnel chamber.
Trays or racks of ampules or vials should be run through the tunnel and
thermocouples placed at strategic locations among the containers.
Bottle-mapping studies may also be conducted during this phase [21]. The
purpose of these studies is to determine possible locations inside the container
that are most difficult to heat. The loading configuration should be identical to
what will be used in production cycles. The major difficulty in doing these
studies is the avoidance of thermocouple wire hang-ups. Thermocouples must
be long enough to be transported through the entire tunnel. A special harness
for thermocouple wires should be constructed for feeding these wires into and
throughout the tunnel.
Repeatability of the thermal process must be demonstrated during these
studies. Peak temperature readings should remain within ±10°C across the belt
for at least three replicate runs.
3. Heat-Penetration Studies
Prior to microbial challenge testing of the tunnel sterilization, heat-penetration
studies must be completed in order to identify the coolest container in the entire
load. Results of heat-distribution studies should aid in predicting where the coolest
location within the load should be. Thermocouples should be deposited at or
near the coolest point inside the container as determined previously from bottlemapping
studies. Normally, the coolest point inside the container is at the juncture
of the bottom of the container and the sidewall. The container’s inner surface
should be in contact with the thermocouple tip because the objective is to
sterilize the inner walls of the container, as well as the inner space.
Three to five replicate runs for each commodity size and every loading
configuration should be done using 10 to 20 thermocouples distributed throughout
the load. Careful analysis of the temperature data after each run will be
Copyright © 2003 Marcel Dekker, Inc.
invaluable in the determination of the cool spot and the repeatability of the
process using the minimum number of replicate runs.
4. Mechanical Repeatability
Tunnel sterilizers must demonstrate mechanical repeatability in the same manner
as batch ovens. Air velocity, air particulates, temperature consistency, and
reliability of all the tunnel controls (heat zone temperatures, belt speed, and
blower functions) must be proved during the physical validation studies.
D. Biological Process Validation of Dry-Heat
Sterilization Cycles
If a dry-heat process is claimed to produce sterile commodities, micro-organisms
known to be most resistant to dry heat must be used to prove the ability
of the dry-heat cycle to destroy them at the coolest location in the load. If the
dry-heat process is claimed to produce both sterile and pyrogen-free commodities,
validation studies must be done using both micro-organisms and microbial
endotoxins. It is the strong opinion of many, including the authors, that biological
validation of dry-heat cycles should be based on the destruction of endotoxin
rather than on the destruction of microorganisms because of the enormous dryheat
resistance of endotoxin compared to micro-organisms [23]. To satisfy the
FDA, however, microbial challenges continue to be done.
With both micro-organism and endotoxin challenges, the cool spot identified
in the heat-distribution and heat-penetration studies will be the logical location
to run the microbial challenge tests. Containers inoculated with microbial
cells or endotoxin will be situated adjacent to identical containers into which
thermocouples are secured to monitor temperature. Temperature profiles must
not deviate from temperature data obtained in earlier studies.
The goal of the biological validation procedure depends on the nature of
the process. If the process is intended to sterilize only, the probability of survival
approach is used. In this case, validation studies must determine a dry-heat cycle
that will assure that the probability of survival of the microbial indicator is not
greater than 10?6. If the process is intended to sterilize and depyrogenate, which
occurs when the materials can withstand excessive heat, the overkill approach
is used. The goal here is to validate a heating cycle that can produce a 12-log
reduction in the biological indicator population.
Equations that apply for determining log reductions or survival probabilities
are Eq. (11) and Eq. (12), respectively. Information that must be known
prior to initiating biological validations include the D value of the biological
indicator to be used, the change in its heat resistance as temperature is changed
(Z value), and the presterilization microbial load on the commodity being steri-
Copyright © 2003 Marcel Dekker, Inc.
lized. Methods for obtaining these values have been adequately described with
ample references in the Parenteral Drug Association technical report on dry-heat
validation [13].
The most widely used biological indicators for dry heat have been spores
of B. subtilis; however, spores of other bacterial species may be used if they are
shown to have greater resistance to dry heat. At 170°C, even the most resistant
microbial spore form will have a D value of 6 to 10 min. At temperatures required
to depyrogenate, microbial spores will have D values of only a few seconds.
The acceptable Z value for microbial dry-heat resistance is 20°C [13].
This value is used primarily in programming computerized temperature-detection
devices, which take temperature data from thermocouple monitors and compute
F values as seen with Eq. (6). A suggested Z value to be used for endotoxin
dry-heat resistance is 54°C [24]. The greater Z value for endotoxin demonstrates
the greater resistance of endotoxin to dry heat.
A suggested step-by-step sequence in the microbial validation of a dryheat
process for sterilizing and depyrogenating large-volume glass containers by
a convection batch oven is presented. Procedures for the validation of a tunnel
sterilization process have been reported by Wegel [25] and Akers et al. [26].
1. The overkill approach is selected for the validation study. This eliminates
the need for bioburden and resistance studies. The objective is
to ensure that the coolest area in the loading pattern, as determined in
earlier heat-penetration and heat-distribution studies, receives sufficient
heat to cause a 12-log reduction in the biological indicator
chosen.
2. Select the type of biological indicator to be used in monitoring process
lethality. Calibrate the biological indicator in its carrier medium
(strip or suspension).
3. Place spore carrier in approximately 12 glass bottles located at the
previously determined coolest area of the oven. Bottles adjacent to
the inoculated bottles should contain thermocouples for monitoring
purposes.
4. Run a complete cycle using the desired loading pattern for future dryheat
overkill cycles.
5. After the cycle, aseptically transfer the spore strip to vessels of culture
media. If spore suspensions were used, aseptically transfer the inoculated
bottles to a laminar airflow workstation and add culture media
to the bottles. Use appropriate positive and negative controls.
6. Determine the number of survivors by plate-counting or fraction negative
methods [13].
7. Use Eq. (10) to determine the number of spore log reductions (SLRs):
Copyright © 2003 Marcel Dekker, Inc.
SLR =
F170
D170
As described in the PDA Technical Report no. 3 [13, p. 48], the overkill
approach usually yields extremely high F values. A minimum F value can be
estimated by assuming one positive unit. In this case, if 12 challenge bottles
were used and if it is assumed that D170 = 1.5 min, Z = 20°C, A = 1 ? 108, and
B = 12/11 then
F = D170(log A ? 2.303 log B)
F = 1.5(8 ? 0.087)
F = 11.87 min
Therefore, an equivalent time exposure at 170°C of 11.87 min will produce
an SLR value of
SLR =
11.87
1.5
= 7.9
If an SLR of 12 were desirable, the process cycle would be extended to achieve
an F170 value of at least
F170 = 1.5(12) = 18 min
If a temperature of 200°C were used and thermocouples located at the coolest
area of the load showed that the bottle interior equaled 200°C or greater for 15
min, the F170 value would be at least
F170 = 15 ? 10[(200?170)/20] = 474 min
It is because of these enormous F170 values obtained during overkill cycles that
several experts strongly advocate the use of endotoxin challenge studies instead
of microbial tests.
E. Endotoxin Challenge in the Validation
of Dry-Heat Sterilizers
The most controversial aspect of endotoxin challenge testing is how much endotoxin
challenge to use. The PDA [13] suggests using a level of endotoxin in
excess of the level expected in the item being subjected to the dry-heat cycle.
Simmons [22] suggested the use of 10,000 ng endotoxin. Akers et al. [26] used
only 10 ng endotoxin.
Papers by Ludwig et al. (27–30) expanded knowledge of dry heat depyrogenation
of glass surfaces using e. coli endotoxin challenges.
Copyright © 2003 Marcel Dekker, Inc.
The step-by-step procedure for the endotoxin validation of a dry-heat process
may be as follows:
1. Inoculate commodity samples with a known amount of endotoxin
(e.g., 10–100 ng Escherichia coli lipopolysaccharide, obtainable from
several commercial sources). The endotoxin should be contained in a
volume of water equal to the residual water volume following the washing
procedure used prior to sterilization.
2. Thermocouples should be placed in commodities adjacent to those
containing endotoxin for temperature monitoring and correlation with
LAL test results.
3. Endotoxin destruction should be ascertained at the coolest location of
the load. Load configurations should be identical to those used in the
microbial validation studies.
4. Several endotoxin challenge samples should be done per cycle, and
the studies must be adequately replicated (3–5 repeats).
5. Following the dry-heat cycle, aseptically transfer the units containing
endotoxin to an aseptic area for extraction procedures, sampling, and
conducting the limulus amebocyte lysate (LAL) test.
6. F values required for endotoxin destruction at various temperatures
and/or cycle time–temperature variations can be determined using a
Z value of 54°C and the following equation:
Fendo. = ?t ? 10(T?170)/54
This approach was used by Akers et al. [26].
When the validation studies described in this section have been completed,
all data are analyzed and a decision is made concerning their acceptability. If
acceptable, the entire validation procedure and all appropriate supporting data
are documented in a bound manual. If the studies are unacceptable because of
unsubstantiated claims of the process or a lack of reproducibility, further testing
must be performed or process variables changed followed by additional validation
studies.
The final document will be reviewed and approved by various plant disciplines
(engineering, microbiology, production, etc.) before the dry-heat sterilizer
is considered fully validated and released for use.
VI. VALIDATION OF ETHYLENE OXIDE
STERILIZATION CYCLES
Ethylene oxide (EtO) has been a sterilant for over 50 years. Yet, while much
attention in the literature has been focused on validation of heat sterilization
cycles, EtO cycle validation has received relatively little attention. Undoubtedly,
Copyright © 2003 Marcel Dekker, Inc.
a major reason is the inability to define accurately the kinetics of microbial
death upon exposure to EtO. This is a result of the complexity of the process,
in which not one but three variables—heat, EtO concentration, and relative humidity—
must be controlled in order to determine D values of microorganisms
when considering EtO sterilization.
The discussion of EtO validation in this section reflects largely what has
been written on this subject since 1977. Several good references [31–35] have
significantly contributed to the rationale, design, and implementation of validation
programs for EtO sterilization cycles.
Five variables are critical to the EtO process. They are EtO concentration,
relative humidity, temperature, time, and pressure/vacuum. Temperature is the
easiest variable to measure and monitor, therefore temperature is used as the indicator
of the worst-case location within the loaded EtO sterilizer. Once the worstcase
location is identified, the validation studies are conducted with the goal of
inactivating a known concentration of indicator micro-organisms in the worstcase
location using a specific loading pattern with a specific EtO cycle with all
variables defined and controlled.
The procedure for EtO cycle validation can be described in eight steps.
1. Address the products specifications and package design. What is the
chemical nature of the components of the product? Do there exist
long and/or narrow lumens that will represent barriers to EtO permeation?
How dense are the materials through which EtO gas must permeate?
What is the nature of the primary and secondary packaging?
Where are dead air spaces within the package and within the load?
By addressing questions such as these, the problems in validating the
EtO cycle can be anticipated and solved at an early stage in the validation
process.
2. Use a laboratory-sized EtO sterilizer during early phases of the validation
process as long as the sterilizer is equipped with devices allowing
variability in vacuum, relative humidity, temperature, gas pressure,
timing, and rate of gassing the chamber. Involve production sterilizer
experts in these early phases of the EtO validation process.
3. Verify the calibration of all instrumentation involved in monitoring
the EtO cycle. Examples include thermocouple and pressure gauge
calibration, gas leak testing equipment, relative humidity sensors, and
gas chromatographic instrumentation.
4. Perform an extensive temperature distribution study using an empty
sterilizer. Identify the zones of temperature extremes, then use these
locations for monitoring during loaded vessel runs. Monitoring will
be accomplished using both thermocouples and biological indicator
spore strips. The most common biological indicator for EtO cycle
Copyright © 2003 Marcel Dekker, Inc.
validation is B. subtilis var. niger. Concentration of these spores per
strip usually is 106. Significant spore survival results will indicate the
need to increase the cycle lethality parameters. It is also prudent to
analyze gas concentration at periodic intervals during the distribution
studies.
5. Do a series of repetitive runs for each sterilization cycle in an empty
vessel in order to verify the accuracy and reliability of the sterilizer
controls and monitoring equipment. Thermocouple locations should
be basically the same for all the heat-distribution studies.
6. Do a series of repetitive heat-distribution and heat-penetration runs
using a loaded EtO sterilizer. The sterilizer should be an industrial
unit in order to ascertain the cycle requirements that will yield consistent
and reliable assurance that all components of the load will be
sterile. The validation procedure should include data collected on both
partial- and full-load sizes. The loading design should be defined at
this point. Dummy loads closely resembling the actual packaging can
be used to test cyclic parameters. Thermocouples and biological indicators
should be placed in a statistically designed format throughout
the load, including areas within the dummy packaged products. The
number of loading patterns, repetitive runs, and the daily timing sequence
of events should all be based upon prior knowledge and experience.
At this point and before proceeding further, the data should
verify the following questions:
a. What is the concentration of EtO released into the vessel?
b. What is the concentration of water vapor in the vessel?
c. What is the range of temperature distribution throughout the
loaded vessel?
d. How much EtO is consumed during the cycle?
e. What are the rates of creating a vacuum and applying pressure?
f. What D value should be used for the biological indicator employed?
g. Does the selected cycle sterilize the product, and what is the estimated
probability of nonsterility?
7. Tests should be conducted on the final packaged product. The protocol
applied should be one that leads to minimal interruption of the
standard manufacturing operations of the facility. Intermediate pilot
plant studies should be carried out to simulate large-scale industrial
sterilization cycles. The EtO cycle documentation should be integrated
into a single protocol. An example of one protocol is as follows:
a. Use approximately 10 biological indicators per 100 cubic feet of
chamber space.
Copyright © 2003 Marcel Dekker, Inc.
b. Place these indicators throughout the load along with thermocouples
at the same locations.
c. Use at least three sublethal exposure cycle times, each in triplicate;
then define the required EtO exposure times using D value
calculations. The exposure time should be increased by an additional
50% to add a safety factor.
d. Perform three or more fully loaded sterilization cycles at the selected
exposure time, monitoring these cycles with thermocouples
and biological indicators.
e. Concomitantly, perform EtO residual tests on the materials exposed
to the desired exposure cycle times from full-load runs.
8. Institute a documented monitoring system primarily relying on biological
indicators, with lesser reliance on end-product sterility testing.
VII. VALIDATION OF VAPOR PHASE HYDROGEN
PEROXIDE STERILIZATION PROCESS
Vapor phase hydrogen peroxide (VPHP) is a relatively new sterilization gaseous
agent that is rapidly becoming the gaseous sterilant of choice for many applications,
the most well known being the sterilization of barrier isolation systems.
Its advantages over other gases, such as ethylene oxide, peracetic acid, chlorine
dioxide, and glutaraldehyde, include the following:
1. It does not require temperatures above ambient.
2. There is little or no concern about residual by-products.
Vapor phase hydrogen peroxide equipment and process are described elsewhere
[36]. The basic steps in the process are dehumidification, conditioning,
sterilization, and aeration. More specifically, there are five steps that must be part
of the validation protocol [36].
1. Cycle development
2. Temperature distribution
3. Vapor distribution
4. Biological challenge
5. Aeration verification
Cycle development parameters include temperature, airflow rate, humidity, liquid
peroxide concentration, liquid peroxide delivery rate, peroxide vapor delivery
temperature, and peroxide vapor half-life. Temperature distribution qualification
involves the use of temperature sensors located throughout the sterilant
delivery line and throughout the enclosure. Vapor distribution qualification uses
Copyright © 2003 Marcel Dekker, Inc.
Figure 8 Capillary filled with a liquid that wets the capillary surface.
chemical indicators to measure VPHP exposure levels. Biological challenges
involve placement of biological indicators, normally Bacillus stearothermophilus
spore strips or stainless steel coupons at many different locations inside the
enclosure, particularly in those areas most difficult for vapor to contact and
sterilize. Aeration verification determines the parameters (e.g., time, air exchange
rates) necessary to reduce VPHP levels within the system to a certain
value, usually ?5 ppm. Vapor phase hydrogen peroxide sterilization cycles are
ultimately validated in the same way as traditional aseptic validation processes
via the use of sterile media fills.
VIII. VALIDATION OF RADIATION
STERILIZATION PROCESS
The major objective in validating a radiation sterilization process, regardless of
whether the mode of radiation is cobalt-60, cesium-137, or electron beam, is to
determine the D value of the indicator micro-organism used to monitor the process.
With radiation sterilization, the D value is defined as the dose of radiation in
Mrads or kilograys* necessary to produce a 90% reduction in the number of indicator
microbial cells. The D value depends on such factors as temperature, moisture,
organism species, oxygen tension, and the chemical environment and/or phys-
*1 megarad = 10 kilogray.
Copyright © 2003 Marcel Dekker, Inc.
ical surface on which the indicator microorganism is present. D values of different
organism species in different suspending media are summarized in Table 7 [37].
Bacillus pumilus spores are the USP choice as the biological indicator for
radiation sterilization. If a probability of nonsterility of 10?6 is specified for a
Table 7 Radiation Resistivities (Expressed as D Values) of Various Micro-organisms
Presence of
D value a “shoulder”
Species (Mrad) (Mrad) Medium
Anaerobic spore formers
Clostridium botulinuma
Type A NCTC 7272 0.12 0.9–1.0 Water
Type B 213 0.11 0.9–1.0 Water
Type D 0.22 0.25–0.35 Water
Type E Beluga 0.08 0.25–0.35 Water
Type F 0.25 0.25–0.35 Water
Clostridium sporogenesa
PA 3679/S2 0.22 0.25–0.35 Water
NCTC 532 0.16 0.25–0.35 Water
Clostridium welchii (perfringens)a
Type A 0.12 0.25–0.35 Water
Type B 0.17 0.25–0.35 Water
Type F 0.20 0.25–0.35 Water
Clostridium tetania 0.24 0.25–0.35 Water
Aerobic spore formers
Bacillus subtilisb 0.06 — Saline + 5% gelatin
Bacillus pumilus E 601c 0.17 1.1 Water
Vegetative bacteria
Salmonella typhimurium 0.13 0.4 Phosphate buffer
R 6008d
Escherichia colie 0.009 — Phosphate buffer
Pseudomonas speciesd 0.003–0.006 — Phosphate buffer
Staphylococcus aureuse 0.02 — Phosphate buffer
Molds
Aspergillus nigerb 0.047 — Saline + 5% gelatin
aRoberts, T. A., Ingram, M. J Food Sci 30:879 (1965).
bLawrence, C. A., Brownell, L. E., Graikoski, J. T. Nucleonics 11:9 (1953).
cVan Winkle, W., Borick, P. M., Fogarty, M. In: Radiosterilization of Medical Products. Vienna:
IAEA (1967).
dThornley, M. J. IAEA Tech. Rept. Series 22 (1963).
eBellamy, W. D., Lawton, E. J. Ann NY Acad Sci 59:595 (1955).
Source: Adapted from Ref. 37.
Copyright © 2003 Marcel Dekker, Inc.
system sterilized by radiation and the D value of B. pumilus in that system is
0.20 Mrad, a radiation dose of 1.2 Mrads would produce a 6-log reduction in
the concentration of B. pumilus spores. Greater probability allowances (e.g.,
10?3) would permit lower radiation doses.*
The development of radiation sterilization cycles follows requirements of
the Association for the Advancement of Medical Instrumentation (AAMI) [38].
1. Determine microbial load on preirradiated products.
2. Determine the D value for natural flora on the product.
3. Determine the D value using biological indicators on the product to
make certain that the natural flora are not more radioresistant than the
biological indicator.
4. Determine the D value of biological indicator spore strips placed
within the product. Determine the location of the lowest radiation
dose point within the product. Then determine the dosage required for
a 10?6 probability of nonsterility for the product.
5. Determine whether or not the D value for the biological indicator
varies as a function of the dose rate. With cobalt-60, dose rate differences
are not of much concern (variance of 0.1–0.5 Mrad/hr), whereas
electron beam sterilization might produce dose rate variances of several
Mrads per min!
The microbiological studies above are conducted to establish the appropriate
dose level to be used to sterilize each specific product or commodity to an acceptable
level of statistical nonsterility. These studies should be conducted following
qualification of the irradiation facility. The Health Industry Manufacturers Associaton
(HIMA) [39] has suggested major items to be included in the qualification
phase of the validation scheme for radiation sterilization installation.
1. Specifications of the irradiator equipment—description, materials used,
instrumentation, etc.
2. Drawings of the equipment and the entire facility
3. Licensing agreement and supporting documentation from both the
Atomic Energy Commission and the appropriate state
4. Reliability and calibration of the dosimeter system
5. Radiation source strength when the sterilization cycle is validated
through D value determination
6. Speed of conveyor belt
7. Dose rate
*Also, validated reduced bioburden (e.g., 0–1 colony-forming units (CFU) per unit surface area or
mL) would allow for a reduction in the radiation dose required to achieve a sterility assurance
level of 10?6.
Copyright © 2003 Marcel Dekker, Inc.
If it is assumed that the radiation sterilizer equipment and facilities have
been qualified and microbiological studies have been conducted as previously
outlined, the next step in the validation process is the complete evaluation of
the radiation sterilization cycle. Tests are conducted to determine the effect of
minimum and maximum product density on the ability of the minimum or nominal
radiation dose—determined during the microbiological studies to produce a
given log reduction in the biological indicator population—to sterilize the load.
For example, it was found that a 0.2-Mrad dose of cobalt-60 will produce a 1-log
reduction in the population of B. pumilus. The microbial load of a one-package
polyvinyl chloride (PVC) device (intravenous administration site) was estimated
to be approximately 1000. A probability of a nonsterility level of 10?6 is desired,
therefore theoretically, the minimum dose necessary to produce a 9-log reduction
in the microbial population is 1.8 Mrad.
Validation tests must be conducted in such a manner that the following
questions are answered:
1. Is the nominal radiation dose sufficient to destroy B. pumilus spore
samples at a relatively high concentration (e.g., 108 spores per ml or
per strip) using a minimum load of product (minimum density)?
2. Is the nominal radiation dose sufficient to destroy B. pumilus spore
samples at a relatively high concentration (e.g., 108 spores per ml or
per strip) using a maximum load of product (maximum density)?
3. What is the radiation sterilization efficiency; that is, how much of the
applied dose is actually absorbed by the product?
4. What is the isodose profile for each irradiated item; that is, what is
the dose of radiation absorbed as a function of the location within the
product being irradiated? What is the ratio between the highest and
lowest doses absorbed within the product?
5. What is the effect of conveyor loading conditions and line speeds on
the amount of radiation absorbed?
As these questions are answered, adjustments probably will be made in
the process. For example, it might be concluded that a higher radiation dose is
required for adequate exposure to all points of a particularly large and/or dense
container system. The loading size or pattern may have to be reduced to permit
adequate sterilization at a given dose level. Once all process parameters have
been defined through preliminary testing, the tedious but essential task of proving
consistency, repeatability, and reliability of the radiation sterilization cycle
must be established. Test records, data work sheets, and monitoring systems
schedules must be kept and organized for easy retrieval and analysis.
While radiation sterilization cycles are validated based upon the achievement
of sterility, many other factors must be considered in the utilization and
approval of the radiation sterilization process. Such factors include the effect of
Copyright © 2003 Marcel Dekker, Inc.
irradiation on (1) the physical appearance of the container system and its contents,
(2) stability of the active ingredient, if present, and (3) safety of the irradiated
material.
IX. VALIDATION OF STERILIZING FILTERS
A. Introduction to Filtration
The following definitions will be helpful in using this section. When filter is
used as a verb (“to filter”) it means to pass a solid–liquid mixture through a
permeable medium to cause a separation of the two. Filter when used as a noun
refers to a device for carrying out filtration, and it consists of the filter medium
and a suitable holder for constraining and supporting it in the fluid path. The
permeable material that separates solid particles from the liquid being filtered
is called the filter medium. The unit operation of filtration, then, is the separation
of solids from a liquid by passage through a filter medium. In many instances,
the filter, including the permeable medium, the means for passing liquid
through the medium, and the process piping, are all referred to by the term filter
system.
In general, filtration objectives can be separated into four basic categories:
to save solids and reject liquids, to save liquids and reject solids, to save both
liquids and solids, and to reject both liquids and solids [40].
As a filtration process proceeds, generally under an applied driving force
of pressure, solids are removed by and begin to accumulate on the filter medium.
The liquid portion continues to move through the filter medium and out
of the filter system. The separated liquid is referred to as the filtrate. The amount
of pressure applied to accomplish the filtration depends on the filtration resistance.
Filtration resistance is a result of the frictional drag on the filtrate as it
passes through the filter medium and the accumulated solids. In equation form,
Filtration rate =
pressure
resistance
(13)
Permeability is often referred to as a measure of liquid flow through a filter
system and is the reciprocal of the filtration resistance.
During filtration, as the particulate buildup continues on the filtration medium,
the filtration resistance increases, or in other words, the filtration permeability
decreases. The capacity of a system, expressed in time, volume of liquid
fed, or amount of solids fed, depends on the ability of the system to maintain
acceptable permeability.
When operating a filtration system, it is important to note the following
general relationship:
Retention ? permeability = constant (14)
Copyright © 2003 Marcel Dekker, Inc.
Therefore, in attempting to have a certain degree of filtration efficiency or retention,
a high rate of filtration, and the lowest possible cost, it is necessary to
make a compromise with one or more of the above factors. A high permeability
or low resistance for large filtration flow rates requires a filter medium of low
retention efficiency. A highly efficient retention will have low permeability, low
flow rates, and higher filtration costs.
B. Sterile Filtration
Production of parenteral drugs requires that the product be sterile. In many
cases, terminal sterilization by heat, ethylene oxide gas, or ionizing radiation is
used to render a product sterile; however, certain products are not stable when
exposed to heat, gas, or radiation, and they must be sterilized by other means.
Filtrative sterilization is suitable in such cases. Indeed, the practice of sterile
filtration is not limited to labile preparations. Unlike the other forms of sterilization,
filtration sterilizes by the removal of the bacteria from the product rather
than by inducing a lethality to the micro-organism. Filtration is straightforward
and reliable; it removes particulate matter other than microbiological; it avoids
possible pyrogenicity owing to the presence of dead bacteria in the dosage form;
it is cost effective and energy efficient; and it allows convenient and flexible
manufacturing systems and schedules with low capital investment [41].
Sterile filtration processes are employed to sterile-filter a product prior to
filling it aseptically into its final containers. Bulk drug solutions are sterilefiltered
prior to aseptic crystallization, thus eliminating the possibility of having
organisms within the bulk drug crystals. The bulk drug can then be processed
into a dosage form aseptically or further processed to be terminally sterilized.
Other filtrative operations reduce the organism content of a final product prior
to terminal sterilizations.
As noted earlier, a highly efficient retentive media will have low permeability,
low flow rates, and higher filtration costs than other less retentive filter
media. The highly retentive filter media used for sterilization have a short useful
life because they clog very easily. Consequently, most filtration processes cannot
be efficiently or economically carried out without the use of prefiltration.
Prefiltration filter media are used to protect and thus lengthen the useful life of
the final membrane filter media by collecting the bulk of the particulate material
so that the membrane filter media must filter out only a small portion of the
particulate. Prefiltration media are normally depth-filter media having a relatively
wide pore and size distribution. A properly selected prefilter must meet
the following conditions: (1) it must be retentive enough to protect the final
membrane filter medium; (2) the prefilter assembly must not allow fluid bypass
under any condition; (3) the prefilter system must be designed to make use of
the prefilter medium; (4) it must have the best retention efficiency (with depth-
Copyright © 2003 Marcel Dekker, Inc.
filter media low pressure differentials and low fluid flux, accomplished by a
multielement parallel design, are best); and (5) the prefilter medium must be
compatible with the solution and not leach components into the solution or
absorb components from the solution. One note of caution needs to be mentioned
in reference to lengthening membrane filter media life. Organism growthrough
can become a problem if filtration takes place over an extended period
of time. During filtration, bacteria continuously reproduce by cell division and
eventually find their way through the filter medium to contaminate the filtrate.
For this reason, prolonged filtration must be avoided. The proposed CGMPs for
large-volume parenterals state that final filtration of solutions shall not exceed
8 hr [42].
Sterilization by filtration is a major unit operation used in aseptic processes.
Aseptic processes require the presterilization of all components of the
drug product and its container. Then all of the components are brought together
in a controlled aseptic environment to create the finished sterile product sealed
within its container/closure system. The level of sterility attained by an aseptic
procedure is a cumulative function of all the process steps involved in making
the product. Therefore, the final level of sterility assurance for such a product
cannot be greater than the step providing the lowest probability of sterility. Each
step in the aseptic process must be validated to known levels of sterility assurance
[43].
This section will concentrate on that portion of the aseptic process wherein
the drug product is sterilized by filtration. From the earlier discussion, sterile
filtration is perhaps a misnomer, since the “sterile” filtrate is almost always
processed further under aseptic conditions, which involves a risk of contamination
[44]. Therefore, to speak of drug product sterilization by filtration as being
as final a processing step as the steam sterilization of a product could possibly
lead to erroneous assurances or assumptions. Since a sterile filtrate can be produced
by filtration, however, we will continue to refer to the process as product
sterilization by filtration.
The primary objective of a sterilizing filter is to remove microorganisms.
The filter medium used to accomplish such an efficient retention may be classified
as one of two types—the reusable type or the disposable type.
The reusable filter media are made of sintered glass, unglazed procelain,
or diatomaceous earth (Table 8). Because these filter media may be used repeatedly
without being destroyed, they are less costly; however, the use of reusable
filter media demands that the media be cleaned perfectly and sterilized prior to
use to prevent microbial contamination and chemical cross-contamination. Even
after exacting and painstaking cleaning processes have been used on reusable
filter media, most companies using sterile filtration have decided that the risk
of contamination is still great and prefer the use of the disposable media that
are used once and then discarded. The remainder of our discussion will concern
the disposable media, often referred to as membrane filter media.
Copyright © 2003 Marcel Dekker, Inc.
Table8 Reusable Sterilizing Filter Media
Type Manufacturer Comments
Diatomaceous earth Allen Filter Company, Fragile to handling, adsorptive altercandles
Toledo, OH ation of solutions, difficult to
clean, leachables, large pore size
Unglazed porcelain Seals Corp. of Fragile to handling and thermal
candles America, Flotron- shock, difficult to clean
ics Division, Huntingdon
Valley, PA
Sintered glass Kimble Division, Ow- Fragile to handling and thermal
ens, IL, Toledo, OH shock, low pressures required,
difficult to clean, smallest pore
4–5.5 µm
Membrane filter media are available from several different manufacturers
and are made from many different materials. (See Table 9.) Filter media consist
of a matrix of pores held in a fixed spatial relationship by a solid continuum.
The pores allow the product solution to pass through the medium while retaining
the unwanted solid particles and micro-organisms. The size of filter medium
pores to retain micro-organisms must be quite small. The 0.20- or 0.22-µm pore
size filter media are considered to be capable of producing sterile filtrates.
The characteristics of a given membrane filter medium depend on its
method of manufacture: whether by phase separation of casting solutions, by
adhesion into an organic union of matted fibers, or by track etching of solid
films [45]. The retention of micro-organisms by the various membrane media,
while not fully understood, has been investigated by numerous researchers who
have indicated that several mechanisms are responsible. The dominant mechanism
of retention is sieve retention. Particles larger than the pore size of the
filter medium are retained on the medium, and as large particles are retained,
pore openings can become bridged and thereby effectively reduce the filter medium’s
pore size. Other possible mechanisms of retention are adsorption of the
particles into the medium itself, entrapment in a tortuous path, impaction, and
electrostatic capture. [46]. The importance of these latter retention mechanisms
has not been fully determined, and on the whole filtration sterilization is treated
as depending on the steric influences of the sieve retention mechanism. The
problem with assuming a sieve retention mechanism is that a sieve or screen
has uniform openings, whereas a membrane filter medium does not. The filter
medium has a distribution of pores, albeit narrow, rather than pores of a singlesize.
In addition, thinking in terms of a sieve or screen conjures up a vision of
precisely measured and numbered openings. Precise methods for computing
Copyright © 2003 Marcel Dekker, Inc.
Table 9 Selected 0.2/0.22 µm Membrane Filter Media
Flow Rate, H2O
Thickness Porosity (ml/min/cm2)
Composition Mfg. Designation (µm) (%) (pressure diff. 10 psi) Autoclave
Mixed ester of cellulose Milliporea MF-Millipore 150 75 21 Yes
Nucleporeb Membra-fil 150–200 75 18 Yes
Cellulose acetate Millipore Celotate 150 71 16 No
Sartoriusc 120 — 18 Yes
Gelmand 130 — 35 No
Nitrocellulose Nuclepore — 150–200 72 17 Yes
MFSe — 140 72 20 Yes
Sartorius — 130 — 18 Yes
Whatmanf WCN 140 72 20 Yes
Polytetrafluoroethylene Millipore Fluoropore 175 70 20 Yes
Nuclepore Filinert 150–200 70 20 (methanol) Yes
MFS Teflon — 78 15 (methanol) Yes
Sartorius PTFE 65 — 9 (isopropanol) Yes
Gelman Teflon TF200 175 — 15 (methanol) Yes
Whatman WTP — 78 15 (methanol) Yes
Nylon Pallg Ultipor N66 — — — Yes
Polyvinylidene fluordie Millipore Durapore 125 75 12 Yes
Polycarbonate Nuclepore — 10 10 15 Yes
Regenerated cellulose Sartorius — 90 — 18 Yes
Gelman Alpha Metricel-200 65 — 28 (acetone) Yes
Polyamide Sartorius — 140 — 18 No
Acrylonitrile/PVC/nylon Gelman Acropore AN200 125 — 20 No
aMillipore Corporation, Ashby Road, Bedford, MA 01730.
bNuclepore Corporation, 7035 Commerce Circle, Pleasanton, CA 94566.
cSartorius Filters, Inc., 26576 Corporate Ave., Hayward, CA 94545.
dGelman Sciences, Inc., 600 South Wagner Rd., Ann Arbor, MI 48106.
eMicro Filtration Systems, 6800 Sierra Court, Dublin, CA 94566.
fWhatman Laboratory Products, 9 Bridewell Place, Clifton, NJ 07014.
gPall Trinity Micro Corporation, Cortland, NY 13045.
Copyright © 2003 Marcel Dekker, Inc.
both numbers and the actual sizes of pores in a filter membrane medium are not
available.
Many approaches have been taken in an attempt to measure the size of
membrane filter media pores [47,48]. Flow measurements, both of air and of
water, have been made. Mercury intrusion under high pressure has been employed,
and pore sizing using either molecular templates or particles, including
bacteria of known size, has been tried. The numerical values for pore sizes from
these methods are based on a derivation from a particular model selected. Each
of the various models has difficulties and shortcomings, and a pore size designation
based on one method does not necessarily mean that a filter medium with
the same designated size but from a different method really is the identical size
[49]. More important, relating such a designated pore size to the membrane’s
ability to retain certain size particles may be anywhere from merely uncertain
to misleading. Therefore, a given membrane filter medium with a designated
pore size of 0.2 micron should not be thought of as “absolutely retaining all
particles greater than 0.2 micron” without challenging the medium with a known
size particulate. In fact, filter media should not be thought of as “absolute retentive”
devices at all. It has been demonstrated that under certain operational
conditions or with certain bacterial challenges, 0.2 micron–rated membrane filter
media can be penetrated by bacteria. Filter media companies do challenge
their products to ensure retention efficiency to sterility [46,50–52].
In addition to the pore size–particle size retention relationship problems
mentioned above, other factors can influence a filter medium’s retention characteristics.
Absorptive retention can be influenced by the organism size, organism
population, pore size of the medium, pH of the filtrate, ionic strength, surface
tension, and organic content. Operational parameters can also influence retention,
such as flow rate, salt concentration, viscosity, temperature, filtration duration,
filtration pressure, membrane thickness, organism type, and filter medium
area [52,53].
The complexity of the sterile filtration operation and the CGMP regulations
require the validation of sterilizing filter systems. The validation of a sterile
filtration operation can be complex, with many operational parameters and
their interactions needing to be identified, controlled, and predicted for each end
product to demonstrate that sterility is adequately achieved by the filtration process.
In the commonly used steam sterilization process, the heat parameters are
identified and in-process controls specified such that a level of sterility assurance
can be reproducibly obtained. In steam sterilization, the important parameter
of heat, measured by temperature, can be accurately measured and continuously
monitored to ensure the operational integrity of the autoclave; however,
unlike steam sterilization, filtration sterilization cannot be monitored on a continuous
basis throughout the process.
The important aspect of filtration sterilization, the membrane filter me-
Copyright © 2003 Marcel Dekker, Inc.
dium—its pore size, pore size distribution, integrity, and capacity—cannot be
monitored during use. Therefore, the prediction that a filter membrane, given a
certain set of operational parameters, will produce a sterile filter is critical. The
only way to test a membrane filter medium’s ability to retain bacteria is to
challenge the medium with bacteria. Unfortunately, after a challenge with bacteria
the filter membrane cannot be used again. Therefore, nondestructive tests
need to be developed by which a filter can be tested as to its suitability for
bacterial retention. Consequently, the approach in filter system validation has
been to establish a reproducible relationship between a membrane’s pore size
and its bacterial retention efficiency. The thinking is that once such a relation
is established, a nondestructive physical test can be developed by which each
filter membrane medium can be tested and its bacterial retention efficiency assured.
Testing of the membrane can then be performed both before and after
use, and if the test results are satisfactory, the filtration process can be deemed
to have been carried out successfully.
C. Nondestructive Physical Tests
for Pore Size Characterization
The theoretical basis for characterizing a membrane filter medium pore size and
pore size distribution is based on the fact that a wet medium is impermeable to
the bulk flow of a test gas until a certain pressure is attained that is sufficiently
high to force the wetting liquid from the medium’s pores. The pressure at which
the transition from a nonflow to a bulk-flow situation occurs can be estimated
in the following manner. First, the assumption must be made that the pores in
the medium can be characterized as parallel cylindrical capillaries of circular
cross section perpendicular to the membrane surface. Even though membrane
pores are not normally found to be cylindrical, the assumption is made that they
can be treated as cylindrical equivalents [48,54]. The transition pressure, P, can
be estimated by equating the forces holding liquid in the cylindrical pores and
the pressure forcing the liquid out of the pores.
In a given capillary of diameter D filled with a liquid that wets the capillary
surface (Fig. 8) at any point along the circumference, the force component
resisting the removal of the liquid is given by
fr = ? cos ? (15)
where
fr = point resistance force component
? = surface tension of the liquid
? = contact angle of the liquid and the capillarywall
Copyright © 2003 Marcel Dekker, Inc.
The total resisting force Fr is found by multiplying the point force fr by the
circumference.
Fr = ?Dfr (16)
Fr = ?D? cos ? (17)
The resisting force Fr and the opposing transition pressure P can be equated,
resulting in
P = Fr (18)
?D2
4
= ?D? cos ? (19)
P =
4? cos ?
D
(20)
For almost all practical purposes, the liquid wets the capillary wall so that the
cos ? is taken as unity and the equation simplifies to
P =
4?
D
(21)
For example, by Eq. (21), the transition pressure for 0.2-µm cylindrical
pores is
P =
4?
D
P =
4 ? 72 dyne/cm
0.2 µm
P = 1440 ? 104 dyne/cm2
P (in psi) = 1.440 ? 107 dyne/cm2 ? 1.450377 ? 10?5 psi/dyne/cm2
P = 209 psi
The cylindrical capillary model predicts that the size of the largest pore present
in a membrane filter medium is inversely proportional to the pressure at which
bulk flow of a test gas is not present.
The bubble point test is a popular single-point physical integrity test for
disc filter membranes based on Eq. (21). A filter medium is wetted with a liquid,
and test gas pressure is slowly raised until a steady stream of bubbles appears
from a tube or hose attached to the downstream side of the filter and immersed
in water (Fig. 9). The pressure at which the bubbles first appear is recorded as
the bubble point and is related to the largest pores in the filter medium. A pore
size can be calculated from Eq. (21); however, it must be realized that the
bubble point test does not measure the actual pore size, but only allows correla-
Copyright © 2003 Marcel Dekker, Inc.
Figure 9 Basic bubble point test setup.
tion of the measured capillary equivalent with some dimensional characteristic
of the pore structure of the membrane medium [49,55].
The bubble point test, while popular, has some deficiencies that must be
realized. First, there is variation in the operator detection of the test end point;
that is, the first appearance of gas bubbles rising in the liquid. Some operators
are able to see smaller bubbles than others. In a recent study, a panel of seven
observers recorded the initial detection of a steady stream of air bubbles rising
from a capillary held under water as the air pressure was gradually increased.
The observers, who had received different degrees of training, identified the
simulated bubble point as occurring at air flows of 5 to 50 mL/min corresponding
to air pressures of 34 and 38 psi, respectively, for a 90-mm disc filter membrane
[56].
In Eq. (21), the surface tension of the liquid (?) is an important parameter
in determining bubble point pressures, and it predicts that liquids of different ?
values will have different pressures for the bubble point. In addition, it is a
common assumption in Eq. (21) that the contact angle (?) is 0, indicating a
complete wetting of the filter medium by the test liquid. Tests have shown that
this might not be a valid assumption in all instances [57]. Different medium
materials show different bubble point values using the same test liquid. The
change in wettability can affect testing before and after autoclaving. Autoclaving
has been shown to wash away filter medium surfactants and thereby decrease
the wettability, thus decreasing the bubble point pressure. Autoclaving
has also been shown to decrease the hydrophobicity of a medium, thereby increasing
the wettability of a membrane resulting in a higher posttest bubble
point pressure [58].
As pressure is increased above the bubble point pressure, pores of decreasing
size have the liquid forced out, and this allows additional bulk flow of the
test gas. By measuring and comparing the bulk gas flow rates of both a wetted
and a dry filter medium at the same pressure, the percentage of the bulk gas
Copyright © 2003 Marcel Dekker, Inc.
flow through the medium pores that are larger than or equal to the size tested
may be calculated. By increasing the test pressures in very small increments and
determining the flow contribution of the corresponding pore size increments, it
is possible to determine a pore size distribution for the filter medium [47,48,59].
The pore size distribution determination is illustrated in Figure 10. Again,
the pore size distribution determination method does not result in the actual
membrane pore size and pore size determination. It does, however, give a means
of comparing different filter media. A narrow pore size distribution is required
for effective filtration and filtration validation.
Another integrity test referred to as the pressure hold test makes use of
the fact that below the transition pressure no bulk flow of the test gas takes
place. Therefore, in a pressure hold test, once a filter system is in place and the
filter medium wetted, pressure is applied to the system and then shut off and
sealed. If there are no leaks in the system or holes in the membrane larger than
the corresponding test pressure used, the pressure should remain constant. If the
pressure drops, there is a leak somewhere in the system that should be corrected.
The pressure hold test is popular in testing filter assemblies and systems in
Figure 10 Pore size distribution determination example. (From Ref. 59.)
Copyright © 2003 Marcel Dekker, Inc.
production situations before and after filtration as a quick integrity check of the
system.
Another problem with the use of the bubble point test develops as one
begins to test large volume disk-type membranes (293 mm) and the pleated
cartridge-type filter media that have large surface areas available for filtration.
Bubble point measurements are inaccurate with these high-surface-area filters
because of several problems. With the larger systems, enough test gas can go
into solution under the test pressure to form visible gas bubbles when the solution
reaches the downstream side of the filter and the test pressure is released.
Observers, seeing the pressure release bubbles, would record the pressure at that
point in the experiment as the bubble point and hence mark the filter medium
as a failure because the bubble point pressure was low, indicative of large pore
sizes in the membrane medium. With the cartridge systems, initial bubble point
gas bubbles tend to rise within the core of the filter rather than leave the filter.
In this case, the first appearance of the bubbles is viewed at a pressure level
higher than the real transition pressure, and defective cartridges could be approved
for use when really unsuitable [58].
With large-surface-area membrane filter media, the interpretation of the
true bubble point can be further complicated because of the diffusion of the test
gas through the media. Because the filter media are more than 70% void space,
a liquid-wetted membrane is virtually a thin film of liquid across which a test
gas will diffuse, governed by Fick’s law.
Q = D(C1 ? C0)?
h
(22)
where
Q = molar flux of test gas per unit area and unit
D = diffusion coefficient for the gas–liquid system used
? = void fraction of the filter medium used
h = thickness of the membrane
C = concentration of the gas; 1 = upstream, 0 = downstream
Because the solubility of the gas in the liquid is low by virtue of Henry’s
law, the solubility can be expressed in terms of pressure.
C1 ? C0 = H(P1 ? P0) (23)
where
H = solubility coefficient for the gas–liquid system
P1 = upstream pressure
P0 = downstream pressure
If the downstream side of the filter vented to the atmosphere then P0 = 0. With
the appropriate substitution, Eq. (22) can be rewritten as
Copyright © 2003 Marcel Dekker, Inc.
Q = DHP?
h
(24)
where P = applied test pressure upstream.
For a given test D, H, ?, and h would be constant. Therefore
Q = KP (25)
and Q should be predictable for a given pressure. As long as the transition
pressure is not reached, Q and P should be linearly related.
Figure 11 shows the wet-flow properties of three hypothetical membrane
filter media. Each filter medium is made of the same material and has the same
thickness and total void fraction. Media A and B have the same oversized pore
size, but A has a broader pore size distribution. Medium C has a pore size
smaller than A and B with a narrow pore size distribution.
The diffusion flow test is not without its difficulties or potential problems,
however; if the filter traps liquid and essentially forms a secondary liquid layer
in addition to the medium, the diffusional flow will, of course, be decreased. A
test pressure that is too low will not be able to differentiate between good media
and media that will pass bacteria because the test pressure will be below even
the largest pore bubble point; the only flow reading obtained will be diffusional
flow through the support media, and they will be almost identical for each size
medium [60]. The recommended single-point diffusion test pressure is 80% of
the bubble point. To run such a diffusion test, the medium to be tested is placed
in its filter assembly and the medium is thoroughly wetted with a liquid and the
filter assembly drained. Pressure from a test gas, generally air or nitrogen, is
Figure 11 Diffusional wet-flow characteristics of three hypothetical membranes.
(From Ref. 61.)
Copyright © 2003 Marcel Dekker, Inc.
then slowly increased up to approximately 80% of the estimated bubble point
pressure for the given medium and liquid used. The resulting flow of test gas is
then quantitatively measured. In the past few years, the sophistication of equipment
to run this test has steadily increased to such a point that some firms now
offer automatic instruments for running diffusion tests [69].
Diffusion tests have been complicated by the diffusion coefficient’s being
changed for the gas–liquid system after the membrane has been autoclaved [58].
With the introduction of additional layers of media material to large cartridge
filters, additional problems have also arisen. The additional media can possibly
affect the drainage of liquid from the filter prior to flow testing. If all of the
liquid is not removed, the possibility exists for additional liquid layers to reduce
the diffusion effectively or for thicker liquid layers in the medium to retard
diffusion. The additional medium material itself adds thickness and therefore
decreases diffusional flow. The reduced diffusion readings, in turn, could mask
larger pores and flaws if this is not dealt with in designing the tests [55]. Additional
nonlinearity with the pressure–gas flow relationship has been reported as
attributable to a process known as liquid thinning. As the test gas pressure is
increased to near the true bubble point of the medium but not below it, the
average thickness of liquid held in the medium decreases. The amount of gas
diffusion per unit pressure therefore increases, and the relationship becomes
nonlinear [60].
The search for the ideal nondestructive test of a sterilizing filter system is
still proceeding. One new suggestion has been proposed to use test gas pressures
above the bubble point. In the meantime, the wise user of filter systems for
sterilization will test in as many ways as possible and correlate for physical tests
with bacterial challenge tests.
There are additional characteristics of filter media that need to be addressed
in a total validation scheme for filter systems. While a thorough discussion
of them is beyond the scope of this discussion of sterilization, they are
mentioned below. Particles and soluble materials can be rinsed from various
process filter media and must be considered as contaminating any parenteral
preparation, therefore steps should be taken to isolate, identify, and eliminate
these contaminating substances prior to use. Solid extractables have been shown
to be pieces of the filter medium itself (media migration) or “cutting” debris.
Soluble contaminants in parenterals have been isolated from filter aids, from
upstream prefilters, and from the sterilizing filter medium itself. In general,
extractables from a membrane filter medium can be categorized into either plasticizers
or surfactants. The surfactants found have been nonionic ethylene oxide
adducts, polyvinylpyrrolidone, long-chain fatty acid–substituted polyethylene
glycol, and alkylated cellulose. The plasticizers have been found to be glycerol
or polyethylene glycol [62]. The filter media should also be tested for compatibility
with each parenteral drug product, presence of induced nonpyrogenicity,
and biological toxicity.
Copyright © 2003 Marcel Dekker, Inc.
D. Filter Qualification
Technical report no. 26 from the Parenteral Drug Association [63] identifies the
following factors that should be part of selecting and qualifying a filter for use
as a product sterilizing filter:
1. Particle-shedding characteristics
2. Extractables
3. Chemical compatibility
4. Adsorption
5. Thermal stress resistance
6. Hydraulic stress resistance
7. Toxicity testing
8. Bacterial challenge testing
9. Physical integrity testing
Physical integrity testing has already been discussed. Subsequent discussion will
focus on extractables and bacterial challenge testing.
E. Bacterial Challenge Test
Microbiological challenging of a filter is the only true means of determining the
bacterial retention properties of the system. Such a test is sensitive because of
the large number of organisms used and because the organism self-replicate and
allow even low numbers of bacteria that might pass through a filter system to
make themselves known.
Filter media are not repetitive-use items, and although used for more than
one lot in production, the media are usually discarded after some predetermined
number of uses or time. Therefore, it is impossible to test every filter medium
individually, since the challenge test is a destructive test. The nondestructive
tests, therefore, require a high degree of correlation with a retention test. When
such correlated tests are established and controls maintained, filtration users can
depend on filtration to produce a sterile parenteral product.
The level of sensitivity of the challenged test is dependent on the challenge
organism, culture environment of the organism, challenge level of the
organism, test volume filtered, challenge rate or the duration of the challenge
test, and pressure used during the challenge test [63,64].
In 1987, FDA published its guideline on validation of aseptic processing
[43] specifying requirements for challenging filters with 107 cells of Pseudomonas
(now Brevundimonas) diminuta per cm2 of filter surface and for validating
aseptic processes using sterile media fills.
The challenge organism utilized in filter testing is Brevundimonas diminuta
(ATCC 19146). The rationale for using B. diminuta follows the same logic
as used in choosing B. stearothermophilus for steam sterilization testing. Bacil-
Copyright © 2003 Marcel Dekker, Inc.
lus stearothermophilus is resistant to heat and therefore severely challenges the
lethality given by an autoclave. Because filtration is a removal process, the
most resistant organism to filtration would be the smallest known bacterium.
Brevundimonas diminuta has been adopted for several reasons. First, the organism
is quite small. The gram-negative rod-shaped cell has a mean diameter of
0.3 µm. The bacteria were first isolated when found to consistently pass through
0.45-µm filter membranes to contaminate filtered protein solutions. The organism
can be grown to high cell densities in a short period of time, and with
proper culturing the cells are small and arranged singly. In addition, B. diminuta
shows only limited biochemical activity. A growth curve for B. diminuta in
saline-lactose broth (SLB) at 30°C is shown in Figure 12. The initial lag time
lasts about 3 hr. In the exponential growth phase, the organism has a population
doubling time (generation time) of 2.6 hr and an instantaneous growth rate constant
(µ) of 0.27 hr?
1. The growth curve levels off in the stationary phase at
approximately 107 cells/mL [65].
For reproducible challenge tests, care must be taken in culturing and handling
the bacteria to maintain bacterial cells of equal morphology. Studies have
shown that differences in cell morphology can be produced by using different
growth media or by the use or nonuse of agitation during culturing. Brevundimonas
diminuta grown in trypticase-soy broth (TSB) without agitation produces a
cell that is distinctly rod-shaped, having a length-to-diameter ratio of 2 to 5.
Grown in the same TSB medium but with 200 rpm agitation, B. diminuta was
more dense and had longer cells with a length-to-diameter ratio of about 4. In
Figure 12 Growth curve of P. diminutia (ATCC 19146) in saline-lactose broth incubated
without agitation at 30°C. (From Ref. 72.)
Copyright © 2003 Marcel Dekker, Inc.
addition, the cells tended to form clusters of from 3 to 8 cells each. Brevundimonas
diminuta grown in SLB without agitation are found to have a length-todiameter
ratio of 1 to 2.5 and are arranged singly [65].
The growth state of a B. diminuta culture is also important in obtaining
the smallest cell size on a reproducible basis. Brevundimonas diminuta cells are
observed to increase in cell size during the lag phase and become smaller during
the declining growth period. Therefore, challenge cells for retention testing are
most appropriate when in the early stationary phase of growth. Early stationary
phase rather than late stationary phase is taken to reduce the chance of the
challenge culture containing nonviable cells and cellular debris, which could
prematurely clog the test filter medium.
Maintenance of a pure culture of B. diminuta must be done in such a
manner as to keep the probability of mutational changes that might alter cellular
characteristics to a minimum.
The microbial challenge test can be performed on a particular filtration
medium, whether disk or cartridge type, by following these general steps:
1. Sterilize the filter system. Figure 13 shows a hypothetical test system
for a disk filter medium.
2. Integrity test the filter medium using a sterile 0.1% peptone solution
or saline solution to wet the medium. The wetting solution also serves
as a negative control sterility check. The entire wetting solution is
Figure 13 Hypothetical disk-filter bacterial challenge test appartus.
Copyright © 2003 Marcel Dekker, Inc.
forced through a sterility control filter, incubated, and checked for
sterility.
3. The bacterial challenge suspension is placed in the appropriate container
and the test filter medium is challenged.
The challenge suspension should have a microbial concentration of
107 B. diminuta per square cm of effective filter area (EFA). Many
challenge levels have appeared in the literature: 107 per 100 ml for 1400
liters, 105–107 per ml, 2–4 ? 105 per liter per min, 1.2 ? 1012–1.9 ? 1013
per liter, and 108 per cm2 EFA [44,50,64–68]. Much discussion has
also appeared in the literature concerning the challenge level and the
potential adverse effects of excessive levels of challenge bacteria [66].
The rationale for the 107 B. diminuta per cm2 EFA challenge is that
while this level of bacteria might not challenge every membrane pore
(approximately 108 pores per membrane medium), it is enough to
challenge any oversized pore. Since the flow through pores varies as
the fourth power of the radius of the pore, a larger fraction of the
total flow is carried by the larger pores. Therefore, it is felt that at
the 107 challenge level enough increased flow will pass through any
oversized pores that challenge bacteria will inevitably encounter an
oversized pore, pass through, and indicate a negative test. The 107
level is also under the filter-clogging concentration [10].
The challenge suspension should be forced through the test medium
at a pressure differential greater than 2 kg/cm2 (approximately 30 psi)
for disk filters and at fluxes of greater than 2 liters per 0.1 m2 up to
around 3.86 liters per 0.1 m2 for cartridge-type filters [64,65]. A pressure
relief valve on the downstream side of the filter should be provided
to allow maximum pressure differentials. The suggestion has also been
made that the pressure be applied full strength immediately rather than
a gradual buildup in order to stress the filter system further [65].
4. The entire volume of the challenge filtrate is subsequently forced
through a sterility test filter system and incubated in the same manner
as the negative control filtrate.
5. A postchallenge integrity test is performed.
6. The challenge test results are then observed. The challenge tests are
considered invalid if the negative control contains any organisms. The
filter system is considered to have failed the test if the filtrate contains
any test organisms.
F. Extractables
Filter validation now includes tests to prove that sterilizing filters do not generate
extractable materials when exposed both to water and to the drug product
Copyright © 2003 Marcel Dekker, Inc.
formulation. Tests for filter extractables may be found in the USP, Section <87>
Biological Reactivity Tests, in Vitro and Section <88> Biological Reactivity
Tests, in Vivo. These tests involve soaking filter material in different solvents,
then evaluating them in two animal models and in cell culture. USP Section
<661> also describes testing of filters to ensure that no extraneous contaminants
are found in the filter material. Filter extracts have been identified as surfactants,
wetting agents, additives used in filter manufacture, higher molecular weight
polymers of the filter polymer, and general particulates [69–71]. Extraction procedures
with actual drug product may include immersing the filter into the drug
product solution, then exposing it to high temperatures and mechanical agitation
before taking samples and assaying by various analytical techniques [71].
G. Retention Efficiency
In the past, several terms have been coined to describe the retention efficiency
of the filter system: beta value, microbiological safety index, reduction ratio,
and titer reduction ratio [64,68,72]. The log reduction value (LRV) is a filter
retention efficiency term that is the logarithm to the base of 10 of the ratio of the
number of organisms in the challenge suspension to the number of organisms in
the filtrate.
LRV = log
N0
N
(26)
LRV = log N0 ? log N (27)
where
LRV = log reduction value
N0 = number of organisms in the challenge
N = number of organisms in the filtrate
With a sterile filtrate, the term log N becomes log 0, which is undefined and is
eliminated from the expression. The LRV is then expressed as being equal to
or greater than N0.
LRV ? log N0 (28)
For example, if a 293-mm-diameter disk filter system having an EFA of 530
cm2 is challenged and the 107/cm2 level is used, the total challenge to the filter
is 5.3 ? 109 organisms. If a sterile filtrate is assumed the LRV would be calculated
and reported as follows:
LRV = log 5.3 ? 109 ? log 0
LRV ? 9.72
Copyright © 2003 Marcel Dekker, Inc.
The probability of passing a single organism through this filter system, or
in other words, the probability of nonsterility (PNS) can be calculated by the
following equation:
PNS =
N
N0
(29)
For the above example, the PNS is calculated as
PNS =
1
5.3 ? 109 = 1.89 ? 10?10
Equations (27) and (29) can be used to calculate the total PNS of replicated
experimental filter challenges. For example, five filter membrane media are to
be challenged at the following P. diminuta levels.
18 ? 109 9 ? 109
5 ? 109 14 ? 109
12 ? 10
The total challenge (N0) is 5.8 ? 1010, and the assumption is made that the
filtrate for each is sterile. The LRV then is
LRV = log N0 ? log N = log 5.8 ? 1010 = 10.76
The PNS then is calculated to be
PNS =
N
N0
= 1.72 ? 10?11, N = 1
These equations may be used to calculate an estimate of the degree of nonsterility
associated with a particular filtration process. In order to determine such a
sterility assurance associated with the process, some knowledge of the initial
microbiological bioburden of the product to be sterilized must be known. If it
is assumed that the microbiological bioburden of a product is 104 organisms and
the product is to be sterilized by filtration through filters from the example
above, the PNS is the sum of all the probabilities of all of the combinations of
the 104 organisms passing through the filter. The expression for this is
PNS = ?
N0
n=1
Pi (30)
where
N0 = the bioburden of the product
Pi = probability of i organisms passing the filter medium
n = 1, 2, . . . i
Copyright © 2003 Marcel Dekker, Inc.
In other words, the PNS is equal to the probability of one organism passing the
filter plus the probability of two organisms passing the filter, and so on. With
the bioburden level greater than one organism, however, there result many combinations
of sets or organisms having a probability of passing the filter. The
probability of all combinations of one organism passing a filter with a given
retention efficiency from a bioburden level N0 can be written as
P1 = N0!
(N0 ? 1)!1
1 ? RV
(31)
where
RV = reduction value
or in logarithmic form
log P1 = log N0!
(N0 ? 1)!1
? LRV (32)
Similarly, the probability of all combinations of i organisms passing the filter is
log Pi = log
N0!
(N0 ? i)i
? i(LRV) (33)
When Eq. (30) is expanded into the format of Eqs. (32) and (33), the following
expression results:
log PNS = ?
log
N0!
(N0 ? 1)!1
? LRV+ 
 
 
 + 
log
N0!
(N0 ? i)!i
? iLRV (34)
In a convergent series, as in Eq. (34), the bracketed quantity representing P1 

P2 
 
 
 
 Pi can be approximated by using P1 only. Therefore, Eq. (34) can be
simplified to
log PNS = log
N0!
(N0 ? 1)!1
? LRV (35)
This simplifies further to
log PNS = log N0 ? LRV (36)
A sterility assurance (SA) can be calculated from
SA = 1 ? PNS (37)
By way of example, the LRV for the previous five-filter example was 10.76. If
a product having a bioburden, N0, of 104 organisms is to be filtered, the PNS
can be calculated using Eq. (36).
Copyright © 2003 Marcel Dekker, Inc.
log PNS = log N0 ? LRV = 4 ? 10.76 = ?6.76
PNS = 1.74 ? 10?7
The SA can be calculated then by Eq. (37) where
SA = 1 ? PNS = 1 ? 1.74 ? 10?7
SA = 0.9999998 or a 99.99998% assurance of sterility
Terminally sterilized parenteral products have a level of SA in the range
of 0.999999. If we assume that our example solution has 100 organisms per
liter, how much could we filter before the SA dropped below 0.999999? By
using Eq. (37)
SA = 1 ? PNS
PNS = 1 ? .999999 = 10?6
When we substitute into Eq. (36) and rearrange
log N0 = log PNS + LRV = ?6 + 10.76 = 4.76
N0 = 57,544 organisms
When we use the following relationship
N0 = C ? V (38)
where
N0 = the bioburden of the product
C = the bioburden concentration per unit volume
V = the volume of the product
then
V =
N0
C
=
57,544 organisms
100 organisms/liter
V = 575.44 liters
Therefore, 575.44 liters can be filtered before going below an SA of 0.999999.
Data generated by the Millipore Corporation show that a mixed cellulosic
ester membrane filter medium with an average bubble point of 3.44 kg/cm2,
when challenged with an average of 2.78 ? 107 organisms/cm2, had an average
LRV of 9.96. Millipore claims that 20 years of quality control testing has confirmed
that mixed esters of cellulose filter media having a minimum bubble test
of 3.3 kg/cm2 or greater will quantitatively retain 107 P. diminuta/cm2 EFA at a
differential pressure of 2.6 kg/cm2. Such is the type of correlative data that are
needed to validate each product for filtration sterilization [69].
Copyright © 2003 Marcel Dekker, Inc.
H. Aseptic Processing [43,73–75]
Aseptic fill processes are validated by simulating production conditions and
using a bacterial culture medium as the product. This process simulation test is
commonly referred to as a “media fill.”
Production facilities must be checked to ensure that all installed equipment
both satisfies the engineering and quality design criteria (installation qualification)
and functions properly (operational qualification). In the performance of a
media fill, it is important that everything be conducted just as a normal production
run. All equipment normally used should be used. All equipment should be
cleaned, sanitized, sterilized, handled, and assembled in a normal manner. All
personnel normally involved in an aseptic process must participate in the media
fill. Such personnel must have sufficient training in such areas as basic microbiology,
personal hygiene, gowning techniques, manipulative techniques, safety,
and cleaning procedures.
Table 10 provides a list of considerations for ensuring that every aseptic
process is appropriately simulated during a media fill validation exercise.
Media fills are conducted to initially qualify a new filling line, a new
product, and/or a change in product container configuration. Subsequent to ini-
Table 10 Considerations for Ensuring Media Fill Runs Adequately Simulate Actual
Production Runs
Duration of longest run
Multiple runs on separate days
Worst-case environmental conditions
Number and type of interventions, stoppages, adjustments, transfers; both planned and
unplanned (e.g., replacing filling needles, pumps, filters, stopper bowl stopping line,
removing all containers, manual stoppering)
Aseptic assembly of equipment
Maximum number of personnel normally present
Number of aseptic additions
Shift breaks, changes, multiple gownings
Number and type of aseptic equipment disconnections and connections
Aseptic sampling
Line speed and configurations
Manual weight checks
Operator fatigue (work time)
Container/closure types run on the line
Temperature and relative humidity extremes
Conditions permitted before line clearance
Container/closure surfaces that contact formulation during aseptic process
Copyright © 2003 Marcel Dekker, Inc.
tial qualification, media fills are required on a semiannual basis to provide minimal
assurance that good aseptic conditions and practices have been maintained.
Initial media fill qualification typically involves a minimum of three consecutive,
separate, and successful media fills. The definition of successful has
evolved from allowing one contaminated unit out of 1000 containers to having
zero contaminated units.
Periodic requalification of aseptic processes with media fills every 6 months
applies to every filling line, every product container configuration, and every
aseptic process operator. Sometimes a requalification media fill will need to be
conducted in intervals of less than 6 months if environmental monitoring data
start failing acceptance limits, if there is personnel change, if a major manufacturing
deviation occurred, or if equipment changes or modifications take place.
A valid change control procedure needs to be in place to ascertain when changes
in the manufacturing environment require a new media fill qualification.
Ideally, the maximum batch size should be simulated in the media fill.
Practically, the number of units filled with media must be sufficient to reflect
the effects of worst-case filling rates, including operator fatigue and the maximum
number of interventions and stoppages. While 3000 vials are needed to
detect with 95% confidence a contamination rate of one in 1000, using 3000
vials as a minimum number of units to be filled is no longer considered to be
sufficient. The current regulatory position is to fill a minimum of 4750 units
three consecutive times with zero positives. One positive in each of three consecutive
runs is viewed as a serious process control problem. The International
Organization for Standardization (ISO) has developed acceptance criteria (the
maximum acceptable contaminated units in a media fill run) as a function of
the number of media fill units.
Following a periodic requalification media fill, production may resume
while media fill units are incubating. No product can be released until media
fill data are analyzed and acceptance criteria are met, however.
Each lot of media must pass a growth promotion test (10 to 100 CFUs
per container) following the media fill run and again after the end of the incubation
period. Typically incubation of media involves a period of 7 days at 30–
35°C to detect bacterial growth, followed by 7 days at 20–25°C for molds.
Incubation conditions must be justified based on favored growth conditions for
common environmental isolates. Prior to incubation, each unit must be inspected,
with any leaking or damaged units removed. Each unit also must be
rolled or inverted prior to incubation for media to contact all interior surfaces
of the container.
Media fill failures can and do occur. Standard operating procedures must
be in place to provide action steps in case of a media fill failure. Typically, if
one of three runs fail, the entire sequence of three separate, consecutive media
fill runs is repeated unless a clear assignable cause can be given to the failed
Copyright © 2003 Marcel Dekker, Inc.
media run. If a requalification media fill fails (one run), there should be criteria
in the procedure to determine whether a single repeat run or a repeat of the
initial qualification (three runs) should be done. All documentation involved in
a production process (e.g., environmental monitoring data and trends, personnel
monitoring data and trends, sterilization charts, HEPA filter certification, filter
integrity test data, handling and storage of all equipment) must be reviewed
after a media fill failure.
For an aseptic filling process the level of sterility assurance is a cumulative
function of all the unit operations involved in the entire manufacturing
system. The final level of sterility cannot be greater than the unit operation
providing the lowest probability of sterility. Adherence to a program that will
enable the validation of all steps in the aseptic process from the solution preparation
step to the final container closing/sealing step will provide the highest assurance
possible that all steps of the process are collectively functioning and
controlled to yield a product that is microbiologically safe.
I. Other Sterile Process Systems Requiring Qualification
and Validation
Historically, and even today, emphasis on the validation of sterile products is
placed mainly on the sterilization processes. No manufacturing operation can be
considered under complete control without qualification of every system that
can potentially affect product quality, however. The following discussion will
touch upon other systems and processes involved in sterile product manufacturing
expected to be validated. Much of this section relies on the following literature
sources [Refs. 43,73–80]. Also refer to other chapters in this book that
discuss certain topics in much greater detail.
J. Facility Design and Construction
The Good Manufacturing Practice (GMP) regulations, FDA, and European Economic
Community (EEC) guidelines on aseptic processing, and other documents
provide comprehensive details on facility requirements for sterile drug production.
The facility must
1. Use HEPA filters for filtering the air supply to reduce or eliminate
particulate contaminants
2. Maintain higher air pressures (positive pressure) within the critical areas
to minimize infiltration of airborne contaminants from outside air
3. Provide smooth, easily cleanable surfaces on equipment, floors, walls,
and ceilings to minimize the opportunity for collection of particulates
and growth of micro-organisms
Copyright © 2003 Marcel Dekker, Inc.
4. Provide temperature and humidity controls appropriate to the product
being manufactured
K. Utility Qualification (see Chapter 12)
Facility design is critical. Likewise, individual utilities require qualification. The
most important of these are heating, ventilation, and air conditioning (HVAC),
water (including clean steam), and compressed gases.
Typical programs begin with installation qualification (IQ). The IQ is described
in a written protocol that contains the following key elements:
1. Equipment or system specifications
2. Spare parts list
3. As-built drawings
4. Wiring diagrams
5. Piping and installation
6. Installation certification statement
Following completion of the IQ, the equipment or system is subjected to
operational qualification (OQ). This is a more rigorous exercise in which the
object is to ascertain that the equipment or system being tested performs in
accordance with design specifications throughout the full operational range(s).
The OQ protocol contains
1. A full system description
2. Calibration certification documents
3. Testing plans
4. Acceptance criteria
5. Full record of testing results
6. Certification statement
1. Heating, Ventilation, and Air Conditioning (HVAC)
Features of the HVAC system that affect product quality (sterility) and therefore
require qualification include
1. HEPA filter integrity
2. Airborne particle control
3. Airflow direction
4. Room air pressure differentials
5. Temperature and humidity control
A popular method for certifying the integrity of the filter installation uses
a polydisperse aerosol, created by blowing air through liquid (e.g., poly-alphaolefin)
introduced into the upstream ductwork, followed by scanning the entire
downstream side of the filter face and periphery with a probe nozzle of an
aerosol photometer. This testing will identify “leaks” caused by damage due to
Copyright © 2003 Marcel Dekker, Inc.
mishandling or faulty construction. Small leaks can be repaired with a suitable
silicone-based compound without removing the filter.
The importance of maintaining air pressure differentials in the enclosures
of the aseptic suite within the ranges specified in the design plans cannot be
overemphasized. Reversal of airflow, which can occur if the relative room pressures
are upset, can allow contaminated air from a noncontrolled region into the
clean room, thus defeating the purpose of the HEPA-filtered air supply.
Most enclosures in the aseptic processing suite are not airtight because of
the need for conveyor lines and pass-through openings, so there is a very real
opportunity for contamination from the noncontrolled adjacent manufacturing
areas and particularly from overhead uncontrolled technical areas.
Special monitoring devices known as Magnahelic or Photohelic gauges
measure the pressure differentials across a diaphragm and depict the value in
terms of inches of water or some other convenient scale. These instruments are
very accurate and sensitive to very small changes in pressure differential. Typically
they are connected directly to an alarm system that will cause a visual signal
(flashing light) or an audible signal (alarm buzzer) and/or trigger a recording device
to report a deviation outside a prescribed range of pressure differential.
2. Water
Water quality is usually defined in terms of chemical and bacteriological purity,
particulate matter content, and endotoxin levels. Potable water is normally from
the municipal water system, which may have been treated with chlorine to control
microbiological growth. Soft water and deionized water have undergone ion
exchange or similar treatment to eliminate unwanted ionic species, such as Mg2+
and/or Ca2+. Purified water, water for injection, and other types of water meeting
compendial specifications are produced by ion exchange, reverse osmosis, distillation,
or a combination of such treatments.
The validation protocol provides a detailed description of sampling locations
and requirements, testing methodology, and test limits or specifications.
Sampling and testing can be performed daily during qualification and validation.
When the system is in routine use, following the validation the testing frequency
can be reduced to a weekly schedule for monitoring purposes.
An action guideline of not more than 10 CFUs/100 ml for bacteriological
purity is suggested. As with the purified water system, the sampling and testing
frequency for the water for injection (WFI) system is defined in the protocol
and can be reduced after the system is qualified and validated.
3. Compressed Gases
Various kinds of compressed gases (e.g., nitrogen, oxygen, and carbon dioxide)
may be found in the sterile drug manufacturing plant; however, as an example
only compressed air will be discussed.
Copyright © 2003 Marcel Dekker, Inc.
Compressed air is one of the utilities that may have direct or incidental
product contact and therefore requires qualification. The types of contaminants
found in compressed air, not surprisingly, are the same as those found in the
ambient environment. These may include micro-organisms (e.g., bacteria, molds,
and viruses), moisture, particulate matter, and possibly pyrogens. Undesirable
levels of hydrocarbons fromcompressor lubricants may be found if the compressor
is not of the oil-free type.
A well-designed compressed air system eliminates or substantially reduces
the levels of these contaminants. Components of such a system include the
following:
1. An oil-free compressor—typically a rotary screw, multiple-stage design
2. An oil-coalescing filter to trap any liquid hydrocarbons or water
3. A dryer to remove condensed moisture and reduce levels of gaseous
hydrocarbons
4. A filtration unit to eliminate gross particulate matter, such as fibers
and metal particles
5. A sterilizing filter rated at 0.2 µm
6. A sanitary design receiver tank and distribution piping sloped for
proper drainage
7. Instrumentation suitable for monitoring the temperature, pressure, and
volume or flow rate in the system
Installation and operational qualification work includes verification of temperature,
pressure, and flow rates, instrument calibration, and thorough flushing of
the entire system to remove oil, metal particles, and other contaminants. The
type of testing and acceptance limits listed in the validation protocol may vary
from firm to firm; however, compressed air with product contact should be
tested for such quality attributes as hydrocarbons, water vapor, and microbial
content (typically less than 0.1 CFU/cu. ft.)
L. Equipment Qualification/Validation (see Chapter 13)
1. Container Preparation
Parenteral drug containers are typically fabricated from glass (bottles, vials, syringes,
or ampules) or plastic (bottles, bags, vials, or syringes). Regardless of
the nature of the container, contaminating substances such as paper fibers, glass
fragments, viable microbes, and pyrogenic materials must be eliminated from
the containers before they are used in the filling operation.
The suitability of the design and utility services is established during the
IQ and OQ phases of qualification discussed earlier in this chapter. Important
criteria for a typical washer include the following:
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Water: quality, temperature, pressure, and flow rate
Steam: quality and pressure
Compressed air: quality and pressure
The duration of the prewash, washing, final rinse, and flush cycles must be
established during validation and maintained within suitably narrow ranges to
ensure repeatability.
One practical approach to validating the cleaning process is to establish a
known level of challenge contaminant, which is applied or “spiked” into numbered
or otherwise identified containers, which then undergo a typical cleaning
cycle. Typical contaminants include visible and subvisible particluate matter and
chemical, microbiological, and pyrogen challenges.
After the wash cycle, the spiked container is evaluated by suitable testing
to determine the amount of residual contaminant. The “before” and “after” numbers
can be compared to establish an efficiency number based on the original
level of contaminant.
Bioburden loading levels were determined by a membrane filtration procedure
prior to washing and also after the spiking to confirm that the desired
challenge level was achieved. Following the cleaning cycle, the same procedure
was used to evaluate residual bioburden. To recover the residual contaminants,
sterile peptone water USP is used to rinse the entire inner surface of each vial.
Results are reported as CFU per vial.
Pyroburden was determined by validated limulus amebocyte lysate (LAL)
techniques both before and after treatment in the washer to confirm pre-existing
and challenge levels. It is expected that pretreatment pyroburdens will be low,
and removal of a known challenge of pyrogen in the cleaning will be low.
Removal of a known challenge of pyrogen in the cleaning procedure provides
assurance that subsequent dry-heat depyrogenation will eliminate any pre-existing
contamination.
2. Closure Preparation
The most common type of primary closure used in conjunction with glass containers
for parenteral drugs is the elastomeric closure. As with the container
itself, the closure must be sterile, pyrogen-free, and free from contaminants that
could adulterate the drug substance, because the closure is likely to be in direct
contact with the drug at some time during the storage, handling, or use of the
dosage unit.
A number of undesirable substances could be present on the surface or
sorbed into the matrix of the closures, but the predominant contaminants are
particles of the closure matrix itself, other rubber compounds, metallic particles,
micro-organisms, endotoxins, and template lubricants, which are usually organic
in nature. In addition, various extractable substances used in the formulation of
Copyright © 2003 Marcel Dekker, Inc.
the elastomeric closure can present problems. These extractable substances include
such activators as ZnO, MgO, and stearic acid; such curing agents as
sulfur and phenolic compounds; such accelerators as amines and thiazoles; and
such antidegradants as dithiocarbamates and various ketones and aldehydes.
Closure sterilization, following the cleaning cycle, is typically done by
autoclaving with saturated steam. The temperatures achieved in such treatments
are not sufficient to eliminate significant endotoxin contamination.
The validation of any cleaning procedure must therefore include testing
for residual endotoxin, particulate matter, and any adventitious contaminant determined
during the pretreatment examination. Achieving sterility during the
cleaning cycle is not an absolute requirement; however, the bioburden remaining
should not present a significant challenge to the subsequent sterilization process
and should be considered in the development of those treatments.
Many manufacturers use equipment that combines the steps of washing,
siliconization, and sterilization in a continuous operation. Such a treatment is
desirable because it minimizes the time the closures are held in a wet condition.
If sterilization does not follow the washing step immediately, the components
must be thoroughly dried to eliminate the likelihood of microbial growth and/
or formation of pyrogens. Closures should be handled in such a manner as to
minimize the potential for contamination from the cleaning operation through
the filling and sealing steps.
3. Filling Equipment
Validation protocols for filling accuracy should specify the number and duration
of filling runs for each size and fill configuration, the filling rates, and the limits
for filling variability considered acceptable to the manufacturer. The purpose of
the validation work is to determine a filling configuration (i.e., line speed, fill
quantity, and container size combination) that will provide the optimum line
speed while maintaining acceptable filling variability. Generally, the higher the
filling rate, the poorer the filling accuracy.
4. Sealing/Capping Equipment
Adequacy of the container-closure system is determined through stability studies
during the development work and is not the subject of the validation project for
the equipment. It is the objective of this phase to demonstrate that the sealing/
capping equipment will consistently apply the overcap in such a manner that
the integrity of the unit is ensured.
Container-closure integrity studies also can be conducted to validate the
sealing efficiency of the capping equipment.
Copyright © 2003 Marcel Dekker, Inc.
5. Lyophilization (see Chapter 9)
During the OQ the following specialized checks should be conducted:
Maximum chamber vacuum under no load
Chamber leak rates under vacuum and pressure
Shelf temperature control (i.e., temperature variation)
Vacuum pumping rate
Chamber heating and cooling rates under no-load conditions to establish
a reference point for future study
Condenser cooling rate
Refrigerant integrity test to verify that coolant does not leak into the
chamber
Condenser drying rate to establish the maximum drying rate of which the
unit is capable
Stoppering mechanism functionality to verify that the mechanism will
properly insert the vial stoppers over the entire range of vials to be used
In addition to the product specifications other attributes peculiar to lyophilized
products should be verified. These may include: uniformity of cake, cake color,
cake height, reconstitution time, moisture content (if not a product specification),
and short-term (accelerated) and long-term stability.
Validation of the lyophilizer cleaning and sterilization processes should
be accomplished. Particular care should be taken to verify that there is no backmigration
of contaminants, whether from adjuvant fluids integral to the equipment
of by cross-contamination from previous product. Typically, an overkill
approach using a sufficient number of thermocouples and biological indicators
is the method of choice. Finally, fill testing to verify the adequacy of the sterilization
procedure and the aseptic manipulations involved with product filling,
transfers, and lyophilization needs to be performed.
M. Environmental Qualification
The effort spent in qualification and validation of the utilities, equipment, and
processes that make up a sterile product manufacturing operation is wasted unless
the manufacturing environment is maintained under control at all times
during production.
The environment of an aseptic filling operation must be monitored and
controlled. Environmental control begins with valid cleaning and sanitization
procedures, then proceeds with adequacy of certified HEPA filtration and clean
room procedures by personnel within the clean room, and is verified by environmental
monitoring techniques. Such techniques include nonviable particulate
Copyright © 2003 Marcel Dekker, Inc.
monitoring of the air (electronic particle counters), surface sampling of equipment
and personnel (Rodac plates primarily; sometimes swab samples), and
airborne viable particulate monitoring (fallout or settling plates, and quantitative
air samplers such as rotary centrifugal samplers or slit-to-air samplers).
APPENDIX I: EXAMPLE PROTOCOL FOR VALIDATION
OF THE STERILIZATION PROCESS
IN A STEAM AUTOCLAVE
Reference No.
Date
I. Purpose:
To provide the method to be used for the validation of the sterilizing
process using an autoclave containing .
II. Scope:
This procedure applies to all steam autoclaves used to process filling
equipment, package components, or final containers. The procedures will
be implemented under the following conditions:
A. The validation of sterilization processes using saturated steam as
the sterilant.
B. Prior to production use of a new autoclave.
C. A change in load design or weight that would result in a load that
is more difficult to sterilize.
III. References:
A. USP.
B. CFR title 21, subchapter E.
IV. Responsibility:
Process validation department.
V. Autoclave identification:
Make
Location
Tag no.
Mfg. serial no.
VI. Load identification:
A. Description.
B. Weight of load
VII. Cycle parameters:
No. of pre-vac pulses
Sterilization:
Temp set point
Temp range
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Exposure time
Dry time
VIII. Equipment and materials:
A. Recording potentiometer.
B. Thermocouples and lead wire harness.
C. Compression fitting for autoclave access port.
D. B. stearothermophilus biological indicators
IX. Procedure:
A. Place 10 thermocouples in the load at the 10 slow-to-heat points, as
determined previously on prot. no. (penetration TC).
B. Place thermocouples exterior and near to the penetration TC and
exposed to the chamber steam (distribution TC).
C. Place one BI at each of the slow-to-heat penetration locations.
D. Load autoclave.
E. Extend TC out of autoclave and attach to recording potentiometer.
F. Position one TC by controller recorder sensor.
G. Close autoclave door.
H. Perform function check of TC. Replace any defectives.
I. Replace autoclave recording chart with a new one, if appropriate.
J. Check to make sure cycle parameters are set.
K. Set potentiometer for a -min scan cycle.
L. Initiate sterilization cycle and potentiometer cycle at the same time.
Time
M. Allow cycle to continue until it is complete. Record the following:
Time process start
Time sterilization cycle on
Sensor TC read
Time sterilization cycle complete
Chamber pressure at cycle initiation
N. Time cycle complete
O. Collect all potentiometer, control, and computer control records and
place with this protocol.
P. Have computer graph results and calculate F0 delivery.
Q. After load has cooled, remove BI and have tested.
R. Incubate BIs in incubator at 55°C for 48–56 hr.
Date on
Date off
S. Similarly, place an untreated control into incubator as in (R) above.
Date on
Date positive
Read by
Date
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X. Results:
BI
Read by
Date
F0 delivery
high
low
XI. Signatures of operators conducting study:
date
date
date
date
XII. Protocol reviewed by: date
XIII. Conclusions:
APPENDIX II: MEDIUM CONSIDERATIONS IN PRODUCT
SIMULATION TESTS
The efficacy of the product simulation test rests on the ability of the culture
medium—manufacture, sterilization, and incubation—to grow contaminating
bacteria. The following outline is from the Parenteral Drug Association, Technical
Monograph No. 2, Validation of Aseptic Filling for Solution Drug Products
concerning growth media, which should be consulted for additional details.
5.2.1. Medium Considerations for Use in Product Simulation Tests
(a) Type of Medium
A number of general microbiological growth media are available
and may be used in a process simulation program. In general, when
selecting a medium for use, the following considerations should be
made:
Selectivity—The medium should have low selectivity; i.e., it
should support the growth of a broad spectrum of organisms including
fungi and yeasts.
Clarity—The medium should be clear to allow for ease in observing
turbidity.
Filterability—Medium should not contain agar or high levels of
suspended solids when a filtration process is used.
Soybean casein digest (SCD)* is currently one of the most fre-
*Use only if testing for anaerobiosis of thioglycollate medium.
Copyright © 2003 Marcel Dekker, Inc.
quently used media, due to its low selectivity and relatively low
cost; however, a partial listing of acceptable media would also include
the following:
• Tryptone glucose yeast extract (TGYE)*
• Brain heart infusion (BHI)*
• Alternate (NIH)* thioglycollate (if an anaerobic growth medium
is desired)
(b) Medium Concentration
The medium of manufacturer’s recommended concentration should
be used when preparing media for process simulation tests unless
other concentrations can be shown empirically to be equivalent.
(c) Medium Utilization
In conducting process simulation tests, there are two basic alternative
techniques available:
1. Use unsterilized medium and filter the medium through the
normal sterilizing membrane hooked directly to the filing
equipment. The media may be prefiltered to reduce bioburden
and increase filtration efficiency.
2. Presterilize the medium in a separate operation. After verification
of medium sterility (such as examining the bulk medium
for absence of growth), use the medium in the process simulation
test. For the test, pass the sterilized medium through normal
processing equipment.
(d) Medium Sterilization
Medium for use in a process simulation test can be rendered sterile
using either moist heat (autoclaving) or filtration. The method chosen
depends on the availability of suitable equipment and the information
desired from the study.
1. Sterilization with Steam
When using this approach it is recommended that
• The medium should be solubilized and dispensed into vessels
with suitable closures to allow for filtered gas exchange
and for subsequent dispensing at the filling line.
The vessel should, if possible, be identical to regular production
equipment.
• The medium should be exposed to steam under pressure
in a validated sterilization cycle to achieve at least a 10?6
probability of survival of organisms within the medium.
• Medium should be cooled slowly to prevent excessive
boiling.
*Use only if testing for anaerobiosis of thioglycollate medium.
Copyright © 2003 Marcel Dekker, Inc.
• Medium is ready for use immediately upon cooling. It
should be inspected for clarity prior to use.
2. Sterilization by Filtration
When using this approach it is recommended that:
• Medium be solubilized at an elevated temperature (50°C)
to facilitate dissolution of the solids.
• Filtration be conducted under normal production conditions
using a sterilizing grade of filter with adequate prefiltration
to increase final filter throughput and life.
• Medium may be stored in bulk vessels following filtration
to ensure that adequate aseptic technique was used.
5.2.3. Media Incubation Parameters
(a) Technique
The filled container with medium should be gently rotated immediately
prior to incubation so that all surfaces, including the closure
(if any), are wetted by the medium. The container should be incubated
in an upright position with the closure uppermost. This posture
minimizes the migration of closure ingredients which might
affect the growth promoting characteristics of the medium.
(b) Time
Media, in the sealed container as delivered from the production
line, should be incubated for a minimum of 14 days.
(c) Temperature
Process simulation test containers should be incubated at suitable
incubation parameters.
The temperature should be monitored throughout the test period
and should be maintained within the specified range for the test
period. Deviations from the specified range should be evaluated
and countered with appropriate action.
(d) Positive Controls
These should be incubated under the identical incubation conditions
as the test containers.
5.2.4. Test Controls
The growth-promoting ability of the medium in the final filled containers
should be demonstrated using filled control containers challenged
with low levels of microorganisms.
(a) Micro-organisms
Compendial micro-organisms—the micro-organisms referenced in
the USP for sterility test growth promotion tests—are suitable for
use as controls. These include the following:
• Bacillus subtilis (spores) ATCC #6633 or Micrococcus lutea
ATCC #9341
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• Candida albicans ATCC #10231
• Bacteroides vulgatus ATCC #8482* or Clostridium sporogenes
(spores) ATCC #11437*
As an alternative to compendial microorganisms, isolates frequently
encountered in the manufacturing environment may be
used to challenge the medium.
A combination of compendial organisms and indigenous organisms
may be used as controls. In all cases, however, microorganisms
used in growth promotion testing should include
both bacterial and fungal species.
(b) Challenge Parameters
Challenge levels not to exceed 100 cells per container should be
used in an attempt to simulate low-level contamination.
Dilutions of actively growing or frozen stock cultures may be
used.
A viable count via a pour plate or spread plate should be obtained
for the final dilution of each micro-organism to verify the
challenge level.
Growth promotion studies should be carried out in duplicate for
each type of micro-organism and each type of container system.
Incubation parameters should be identical to those of the test
medium.
(c) Interpretation of Results
Medium is acceptable if growth is observed in at least one of the
two test containers for all of the challenge micro-organisms.
If no growth is observed in both of the challenged containers,
one repeat test may be conducted to rule out laboratory error. On
the repeat test, both containers must support growth.
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67. Stone, T. E., Goel, V., Leszczak, J. Methodology for analysis of filter extractables:
A model stream approach. Pharm Tech 18:116 (1994).
68. Johnston, P. R., Meltzer, T. H. Pharm Tech 3(11):66 (1979).
69. Meltzer, T. H., Jornitz, M. W. Filtration in the Biopharmaceutical Industry. New
York: Marcel Dekker (1998).
70. Reif, O. W., Solkner, P., Rupp, J. Analysis and evaluation of filter cartridge extractables
for validation in pharmaceutical downstream processing. J Pharm Sci Tech
50:399–410 (1996).
71. Stone, T. E., Goel, V., Leszczak, J. Methodology for analysis of filter extractables:
A model stream approach. Pharm Tech 18:116 (1994).
72. Pall, D. B., Kirnbauer, E. A. Bacterial removal prediction in membrane filters.
Proceedings of 52nd Colloid and Surface Science Symposium, University of Tennessee,
Knoxville, June 12, 1980.
73. Validation of Aseptic Filling for Solution Drug Products. technical monograph no.
2. Philadelphia: Parenteral Drug Association, pp. 16–21 (1980).
74. U.S. Food and Drug Administration. proposed revised Guidelines on Sterile Drug
Products Produced by Aseptic Processing. Rockville, MD: FDA (Nov. 30, 1998).
75. Carleton, F. J., Agalloco, J. P. Validation of Aseptic Pharmaceutical Processes.
New York: Marcel Dekker (1986).
76. Hofmann, K. L. Sterile products validation. In: I. R. Berry, R. A. Nash, eds. Phar-
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maceutical Process Validation. 2nd ed. New York: Marcel Dekker, pp. 89–166
(1993).
77. Cloud, P. A. Pharmaceutical Equipment Validation—The Ultimate Qualification
Guidebook. Englewood, CO: Interpharm Press (1998).
78. DeSain, C., Sutton, C. Facility qualification studies. Biopharm 38–41 (Jan. 1998).
79. Collentro, W. V. Pharmaceutical Water—System Design, Operation, and Validation.
Englewood, CO: Interpharm Press (1998).
80. Anderson, N. R. Container cleaning and sterilization. In: W. P. Olson, M. J.
Groves, eds. Aseptic Pharmaceutical Processing. Prairie View, IL: Interpharm
Press (1987).
Copyright © 2003 Marcel Dekker, Inc.
5
Validation of Solid Dosage Forms
Jeffrey S. Rudolph
St. Augustine, Florida, U.S.A.
Robert J. Sepelyak
AstraZeneca Pharmaceuticals LP, Wilmington, Delaware, U.S.A.
I. INTRODUCTION
In this chapter, emphasis will be placed on the validation of solid dosage forms,
from the early stages of product development through pilot scale-up and the
commercial manufacturing process. The objective is to present an overview and
to discuss aspects of validation in terms of pharmaceutical unit operations; that
is, those individual technical operations that comprise the various steps involved
in product design and evaluation. The focus of the discussion will be on tablets,
but consideration will also be given to hard gelatin capsules. The concept of
process validation from its beginnings in the early 1970s through the regulatory
aspects associated with current good manufacturing practice (CGMP) regulations
and the application thereof to various analytical, quality assurance, pilot
plant, production, and sterile produce considerations will be discussed elsewhere
in this book [1,2].
Although the original focus of validation was directed toward prescription
drugs, the FDA Modernization Act of 1997 expanded the agency’s authority to
inspect establishments manufacturing over-the-counter (OTC) drugs to ensure
compliance with CGMP, thus establishing documented evidence that specific processes
or equipment will consistently, and with a high degree of assurance, produce
a product that meets predetermined specifications and quality attributes [3].
All pharmaceutical scientists, whether in development, quality assurance,
production, or regulatory affairs, are familiar with the axiom that quality is not
Copyright © 2003 Marcel Dekker, Inc.
tested into a product but rather is built in. This is an important concept, since it
serves to support the underlying definition of validation, which is a systematic
approach to identifying, measuring, evaluating, documenting, and re-evaluating
a series of critical steps in the manufacturing process that require control to
ensure a reproducible final product. Dr. Chao [4] has enumerated four key elements
that form the basis of a prospective process validation program.
1. Definition of the desirable attributes of the drug product or components
thereof as well as those characteristics that are not desired
2. Establishment of limitations or constraints for these attributes
3. Determination of the controls or testing parameters that will be measured
or tested
4. Initiation of studies to establish control or boundary limits for those
key attributes that influence the product, process, quality, and performance
These criteria represent a logical progression of activities encompassing the development
of a pharmaceutical product.
There are several important reasons for validating a product and/or process.
First, manufacturers are required by law to conform to CGMP regulations. In the
early 1990s, the concept of preapproval inspection (PAI) was born and had as one
of its basic tenets the assurance that approved validation protocols and schedules
were being generated and that comprehensive development, scale-up, and biobatch
and commercial batch validation data were required in order to achieve a successful
regulatory PAI audit [5–9]. Second, good business dictates that a manufacturer
avoid the possibility of rejected or recalled batches. Third, validation helps to
ensure product uniformity, reproducibility, and quality [10–12].
Most discussions of product and process validation that have been published
[13–15] or that have been the subject of presentations at meetings have
concentrated on validation associated with the full-scale manufacture of pharmaceutical
processes and how equipment processing variables affect the overall
quality of the finished product. Although this is certainly an important aspect of
product validation, validation of numerous earlier aspects of development are
critical to the subsequent phases of the process.
Without proper characterization, specification, and control of these earlier
development steps, the foundation will be weak and will not support the evolving
product when it is challenged during the formal validation of pilot and
production batches.
II. VALIDATION OF RAW MATERIALS
The validation process of a solid dosage form begins with a validation of the raw
materials, both active pharmaceutical ingredients (APIs) and excipients [16–19].
Copyright © 2003 Marcel Dekker, Inc.
Variation in raw materials is one of the major causes of product variation or
deviation from specification. The API may represent the most uncontrollable
component in the complete product/process validation scheme, as key physical
properties such as morphology and particle size/surface area may not be completely
defined this early in the sequence. Often times the synthesis of the new
API (drug substance) is not finalized, and changes occur during the development
of the compound.
The preformulation program initiated during the early exploratory phase
of product development is rarely considered part of validation, but it represents
one of the more critical steps in the development cycle. Chemical characteristics
such as drug impurities and impurity levels can affect the stability of the product.
Physical properties such as drug morphology, solubility, and particle size/
surface area are important in assessing drug availability. The particle size, shape,
and density of the drug can affect material flow and blend uniformity. The
hygroscopic nature of the drug can be important in both the handling the material
and the reproducibility of the manufacturing process [20].
For example, a water-insoluble drug is usually milled or micronized in
order to achieve rapid dissolution and in vitro availability [14]. Since particle
size is inversely related to surface area, large surface areas (0.5–5 m2/g) are
created during a particle reduction process. Particle size is directly interrelated
to several key processing variables. Several of the most significant are flow,
blend uniformity, granulation solution/binder uptake, compressibility, and lubricant
efficiency [21]. In order to achieve a uniform blend of active ingredient
with other formula components, either for subsequent wet granulation or direct
compression processing, it is critical that the active ingredient be compatible
with the other ingredients in terms of particle size, density, and shape in order
to permit a random distribution of ingredients within the blend prior to compression.
If the milling or micronizing process is not controlled and properly validated
so as to achieve a reproducible particle size distribution, irregularities in
blend distribution will result in content uniformity problems of the final dosage
form [22].
Another manufacturing characteristic that may be affected negatively by
not validating the active ingredient particle size distribution/surface area is the
volume of granulating solution or binder needed to produce a properly agglomerated
mass. A greater volume of granulating agent will be needed to wet-mass
a powder bed comprising finely divided particles than is needed for coarser
particles of the same substance. If the particle size/surface area ratio is not
controlled and a specific amount of granulating solution is not stated in the
product manufacturing directions, then in some cases the wet mass will be overwet,
resulting in erratic drying properties (case-hardening, insufficient dried
product), or in contrast, it will be too dry and will not form proper granules,
resulting in poor granulation flow, poor tablet compressibility, and content uniformity
problems with the final dosage form.
Copyright © 2003 Marcel Dekker, Inc.
The certification/validation of excipients used in solid oral dosage forms
is also extremely important [23]. Excipients can represent less than 1% of a
tablet formula or as much as 99%. It is no less important to validate the critical
characteristics of the 1% material than of an excipient used in larger quantities.
Factors to be aware of are (1) the grade and source of the excipients, (2) particle
size and shape characteristics, and (3) lot-to-lot variability.
Three specific examples illustrate this point.
1. Microcrystalline cellulose is widely used in solid dosage forms as a
diluent. It is manufactured in different grades and by different companies.
There can be significant differences in the chemical composition,
crystallinity, and particle size/size distribution between different microcrystalline
cellulose lots [24]. Besides differences between manufacturers,
differences can be seen with the same company using different
manufacturing sites, raw materials, and/or manufacturing processes
[24–27]. Differences in the particle size/size distribution of microcrystalline
cellulose can affect the wet granulation step and/or blend
uniformity of a tablet formulation [28]. With direct compression formulations,
differences in particle size distribution between lots can
result in (1) the initial mix not actually being uniform when using the
validated processing parameters, or (2) materials segregating during
compression. A smaller particle size will require additional binder
solution to granulate the materials due to the greater surface area of
the microcrystalline cellulose. This could result in granules having
greater strength, which could decrease the tablet dissolution rate.
The dissolution rate of prednisone was shown to vary due to the
particle size and chemical composition of microcrystalline cellulose
[29].
2. Magnesium stearate is used as a lubricant to reduce friction when
removing the solid dosage form from its molding process. It is well
known that the action of magnesium stearate is highly dependent on
its particle size and its ability to delaminate its “deck of cards” configuration
when stress is applied, thus creating a slipping action that
relieves the applied stress [30]. It is also well known that when magnesium
stearate is used in excess, the disintegration and dissolution
characteristics of the final tablet or capsule are usually hindered as a
result of a hydrophobic coating of the formula components. This coating
action can also be achieved by using a smaller particle size or
greater surface area lubricant. The smaller particle size lubricant more
efficiently coats the surface of the particles, thus creating more hydrophobicity
and subsequent drug-release problems. Lot-to-lot variability
and differences between manufacturers have been shown to affect tab-
Copyright © 2003 Marcel Dekker, Inc.
let properties (e.g., tablet hardness) and performance (e.g., dissolution)
[31–34]. It is critical to validate the particle size/surface area
characteristics of a supplier’s grade of magnesium stearate to ensure
that there is relatively good assurance that the stearate is uniform lot
after lot. Also, when an alternate source of stearate is sought, it is
critical to check the particle size/surface area and shape characteristics
to ensure that these parameters do not vary significantly from the
primary source material. If these criteria are different, a more in-depth
study, possibly using an instrumented tablet machine, would be appropriate
to ensure that alternate source stearate does not cause compression
or ejection problems. Dissolution testing would also be conducted
as a companion test, again to ensure that the new stearate did
not create in vitro drug release problems.
3. The importance of validating a raw material can also be illustrated in
the case of dyes used to impart a color to a tablet. Consider the use
of an aluminum lake dye that is dry-blended into a direct compression
tablet formulation. In order to achieve an even color distribution, the
colorant should be added using a geometric addition or preblend approach.
Unless the dye is available as a finely divided, large surface
area material that is free from agglomerates, the resulting tablets will
be mottled and have areas of high dye concentration, which may yield
a speckled tablet appearance. The validation of colorant raw materials
using such techniques as particle size analysis, surface area measurements,
and Hegman gauge testing is critical to ensure that all lots of
dye material received will repeatedly perform in a successful manner
when incorporated into pharmaceutical dosage forms.
A comprehensive program for establishing validation and control procedures
for raw materials is critical if one is to achieve a product that meets all
of the final product criteria batch after batch.
Variations in raw materials constitute one of the major sources of problems
confronting the pharmaceutical development scientist, production supervisor,
or quality control chemist. Variations in materials occur among different
suppliers of the same product, depending on the method of transportation chosen,
the exposure of materials to undesirable conditions (heat, humidity, oxygen,
light), the reliability of the supplier, and the individual supplier’s conformance
to regulatory requirements in terms of facilities, personnel, operating procedures,
and controls. In addition to the important physical characteristics of particle
size, surface area, and the like mentioned previously, the manufacturer
should check the supplier’s assay procedure as part of its own validation program.
Other chemical characteristics, such as water content, residue on ignition,
and heavy metals, should also be monitored.
Copyright © 2003 Marcel Dekker, Inc.
The steps involved in the validation of a raw material or excipient follow
those cited in the CGMPs and in the formal written documentation of those
procedures and methods used.
1. Each raw material should be validated by performing checks on several
batches (at least three) from the primary supplier as well as the
alternate supplier. The batches chosen should be selected to represent
the range of acceptable specifications, both high and low.
2. Depending on the susceptibility of the raw material to aging, physical,
chemical, and/or microbiological stability should be assessed. This is
especially true for liquid or semisolid ingredients, in which interaction
with the container or permeability of the container to air and moisture
could have a detrimental effect on the raw material.
3. Once the samples of raw materials have been selected as having fallen
into an established, acceptable range of specifications and stability, it
should be used to manufacture a batch of the final dosage form. It
may be appropriate to manufacture several lots of final product with
raw material at the low and high ends of the specification limit. Such
testing would be especially useful when it is known that the product
may be sensitive to small changes in the characteristics of the excipients
or active ingredient.
4. The final step of raw material validation should involve an on-site inspection
of the supplier to review the vendor’s manufacturing operations
and control procedures. The reliability of each vendor and how well
each conforms to regulatory requirements must also be determined.
III. ANALYTICAL METHODS VALIDATION
The topic of analytical methods validation will be discussed elsewhere in this
book in great depth. It is important, however, to enumerate the key elements of
this subject at this time. In August 1994, the FDA issued a memo providing
direction for the certification of laboratories. Areas discussed in that document
included analytical methods validation [35]. Unless a suitable analytical method
or series of methods is available to assess the quality and performance of a solid
dosage form, the validation program will have limited value. Recently a review
article was published focusing mainly on validation criteria and how to validate
[36]. The following list of analytical criteria must be assessed prior to beginning
any validation program:
1. Accuracy of method: The ability of a method to measure the true
value of a sample.
Copyright © 2003 Marcel Dekker, Inc.
2. Precision of method: The ability of a method to estimate reproducibility
of any given value, but not necessarily the true value.
3. Specificity: The ability to accurately measure the analyte in the presence
of other components.
4. In-day/out-of-day variation: Does the precision and accuracy of the
method change when conducted numerous times on the same day and
repeated on a subsequent day?
5. Between-operator variation: Repeat of the precision and accuracy
studies within the same laboratory using the same instrument but different
analysts to challenge the reproducibility of the method.
6. Between-instrument variation: How will different instruments within
the same laboratory run by the same analyst affect the accuracy and
precision of the method?
7. Between-laboratory variation: Will the precision and accuracy of the
method be the same between the development and quality control
laboratories?
A collaborative study between various analytical methods chemists who developed
the analytical method and the analytical chemists in the quality control
laboratory who must routinely run the method will help to ensure the validity
and ruggedness of the analytical method. If characteristics of the analytical
method are found to be less than optimum or if deficiencies arise during testing,
the method should be returned to the originating chemist for re-evaluation.
When a method is being developed, it is important that the analytical
chemists developing the methods be cognizant of the laboratory conditions in
which the methods will be conducted in a quality control setting.
The methods chemist must be able to make the method work when operating
conditions of time, instrument limitations, and other techniques that could
“baby” the method are not used. Normal operating conditions in quality control
laboratories require a robust method that can be run routinely by different chemists
on different instruments in a high throughput mode. In some cases, the
method should be automated to take advantage of greater laboratory efficiency.
It is the responsibility of the analytical methods development chemist to build
these important elements into the methods.
The responsibilities for suitable validated analytical methods, however, do
not rest solely in the analytical method development group. Today the analytical
function uses new and sophisticated chromatographic and other instrumental
techniques that require a high level of technical expertise. It is the responsibility
of quality control management to ensure that its staff is adequately trained and
its laboratories properly equipped so that new analytical methods can be properly
transferred from an analytical methods group to the quality control department.
A mutual understanding of each other’s responsibilities and limitations is
Copyright © 2003 Marcel Dekker, Inc.
necessary in order to develop the trust that is required between these two important
functions.
Outsourcing the development, validation, and performance of analytical
methods in recent years has become a popular means to facilitate movement of
product through the development process. A recent industry survey reported that
the vast majority (86%) of the companies responding say they outsource analytical
methods development to contract laboratories. Twenty-five percent of the
responding firms indicated that they “often” or “always” contract out stability
testing on development compounds [37]. There are important criteria to follow
in working with contract laboratories to ensure that their methods validation
procedures yield results that are consistent with those of the client company
[38]. This topic will be discussed later in this chapter.
IV. EQUIPMENT/FACILITY VALIDATION
The product development of a pharmaceutical product has its origins in a systematic
approach to formulation, process and manufacture, and the analytical
testing that is necessary to monitor quality and reproducibility. Once development
scale activities (product development, early toxicology, and clinical evaluation)
provide encouragement that the development compound could become a
commercial product, a multidepartmental team is usually formed with product
development, production, and engineering staff to plan a life-cycle approach
related to the manufacture of the product. For large products, a master plan
approach combining elements of project definition, coordination, administration,
scheduling, and budgeting is progressed to ensure that all elements of the multicomponent
plan are efficiently and successfully identified, communicated, progressed,
monitored, and delivered.
Process equipment used in the development phase is assessed relative to
its suitability for large-scale manufacture. Alternate equipment is identified and
evaluated and a final decision rendered. Existing or new equipment to be used
to manufacture the new pharmaceutical product must then undergo a comprehensive
evaluation called a validation protocol. This protocol can be divided
into a number of components, but usually has design qualification, installation
qualification, operation qualification, performance qualification, maintenance
(calibration, cleaning, and repair) qualification, and closure qualification as integral
components [39]. These qualification steps will be discussed in detail in
elsewhere in this book. Contrary to popular belief, new equipment and systems
sometimes can be more challenging to validate than well-worn older ones. New
systems have no use history (operational and maintenance), which can be valuable
information that can simplify protocol writing and subsequent validation
[40].
Copyright © 2003 Marcel Dekker, Inc.
Once the full-scale manufacturing equipment and process have been identified,
it is important to either ensure that an existing physical facility is available
in which the product can be manufactured or determine if a modified or
new facility is required. Once these decisions have been made, a validation
commissioning document (VCD) is prepared that identifies the shared responsibility
and cooperation that must occur among the owner, construction manager,
and vendors [41–43]. A commissioning program that is well planned will facilitate
the validation process, accelerate start-up, enhance documentation, and ensure
that the pharmaceutical product is produced in a GMP-compliant facility.
The VCD would usually be prepared by a validation specialist and approved by
the facility’s project manager. It would be very comprehensive and would include
purchase orders, process flow diagrams, operation and maintenance manuals,
installation requirements and factory acceptance testing results, heating,
ventilation, and air conditioning (HVAC) requirements and test results, calibration
procedures, software specifications, and staff training.
A practice has evolved in the qualification of a pharmaceutical facility
that is simply to commission certain systems deemed noncritical rather than to
validate them. It is important to point out that commissioning should not be a
substitute for validation but rather used as a tool to aid in the entire validation
process [44].
V. DEFINITION AND CONTROL OF PROCESS VARIABLES
Process validation can be defined as a means of challenging a process during
development to determine which variables must be controlled to ensure the consistent
production of a product or intermediate. It also provides the means for
an ongoing quality audit of the process during the marketing phase of the product
to ensure its compliance with these specifications. It is based on the concept
that the process employed has been optimized, so that data generated through
the testing program may be considered credible and evaluated for consistency
as well as relevance. The activity starts when the pharmaceutical development
department begins its work. Pertinent data or information are collected during
the preformulation stage, and additional inputs are generated during formulation
development and evaluation, process development, and full-scale manufacture.
The information gathered in all four stages is evaluated to determine which
parameters in the process can be used as possible tools to show that the product
is under proper control. Once this is done, some other major steps in the development
of a validation program are as follows:
1. Obtaining test data to determine the numerical range of each parameter
e.g., assess the tablet hardness over a series of batches that
achieves an acceptable friability, disintegration, and dissolution.
Copyright © 2003 Marcel Dekker, Inc.
2. Establishing specification limits from the test data derived for a given
parameter. Based on the data collected and using statistical techniques,
determine the extremes of acceptable hardness (high and low)
that would provide 95% assurance that the friability, disintegration,
and dissolution specifications would be met (upper and lower control/
release limits).
3. Determining how well the specification limit indicates that the process
is under control. Challenge the process by producing product at the
extremes of the specification limit to ensure all product specifications
are met.
4. Certifying the equipment that is used in obtaining the data and controlling
the process. Ensure that equipment operating conditions (e.g.,
rpm, temperature, power utilization) are within specification limits
under variations of product load.
Once this has been done, one can proceed to actual product testing utilizing
these parameters and their specifications to validate that the process will
produce acceptable product. The testing can be conducted on samples during
the manufacture (in-process tests) or on the finished product (finished product
tests). Each product may have its own idiosyncrasies requiring special tests, but
generally the in-process and finished product tests that would be required for
all solid dosage forms in process validation are as follows.
A. In-Process Tests
1. Moisture content of “dried granulation”: Loss on drying (LOD) can
be used to determine whether or not the granulation solvent has been
removed to a sufficient level during the drying operation (usually less
than 2% moisture).
2. Granulation particle size distribution: An extremely important parameter
that can affect tablet compressibility, hardness, thickness, disintegration,
dissolution, weight variation, and content uniformity. This
parameter, which can be done by sieve analysis, should be monitored
throughout the tablet validation process.
3. Blend uniformity: Samples of the blend are taken and analyzed to
ensure that the drug is uniformly dispersed throughout the tablet/capsule
blend. The proper blend time must be established so that the
blend is not under- or overmixed. The sampling technique is critical
for this test to be valid [45].
4. Individual tablet/capsule weight: The weight of individual tablets or
capsules is determined throughout compression/encapsulation to ensure
that the material is flowing properly and the equipment is work-
Copyright © 2003 Marcel Dekker, Inc.
ing consistently. The individual weight should be within 5% of the
nominal weight. Weight fluctuations or frequent machine adjustments
suggest that the formulation/process (e.g., poor granulation flow) is
not optimized and/or that the equipment may need maintenance.
5. Tablet hardness: Tablet hardness is determined periodically throughout
the batch to ensure that the tablets are robust enough for coating,
packing, and shipping and not too hard to affect dissolution.
6. Tablet thickness: Tablet thickness is also determined periodically
throughout the batch and is indirectly related to the hardness. It is
another indication of whether or not the formulation has proper flow
and compression properties.
7. Disintegration: Disintegration is determined during the manufacture
as a predictor of tablet performance (e.g., dissolution).
B. Finished Product Tests
1. Appearance: The tablets should be examined for such problems as
tablet mottling, picking of the monogram, tablet filming, and capping
of the tablets. If the tablets are colored, the color quality needs to be
examined.
2. Assay: This test will determine whether or not the product contains
the labeled amount of drug.
3. Content uniformity: Samples are taken across the batch profile (beginning,
middle, and end) and analyzed to ensure that the dosage forms
comply with compendial standards (±15% of the labeled amount) or
more stringent internal limits. It will indicate whether there is demixing
during the manufacturing operation (i.e., segregation during flow
of granulation from a storage bin).
4. Tablet hardness: A critical parameter for dosage form handling and
performance.
5. Tablet friability: Friability is an important characteristic on the tablets’
ability to withstand chipping, cracking, or “dusting” during the
packaging operations and shipping.
6. Dissolution: Dissolution is important to ensure proper drug release
characteristics (in vitro availability) and batch-to-batch uniformity.
These key test parameters are the yardsticks by which the major processing variables
in solid dosage forms are evaluated. Some processing variables are:
Mixing time and speed in blenders and granulators
Solvent addition rates in granulators
Time, temperature, and airflow conditions in dryers and coaters
Screen size, feed rate, and milling speed in mills
Copyright © 2003 Marcel Dekker, Inc.
Machine speed and compression force in tablet presses
Machine speed and fill volume in encapsulators.
Process validation testing is generally done on the first three batches of product
made in production-size equipment. Revalidation testing is only done when a
“significant” change has occurred. A significant change is one that will alter the
in-process or final product specification established during the validation program
or a change in formula, process, or equipment.
VI. GUIDELINES FOR PROCESS VALIDATION OF SOLID
DOSAGE FORMS
Numerous factors should be considered when developing and validating solid
dosage forms. Figures 1 and 2 are flowcharts for the validation of newand existing
processes. As a means of providing a broad overview of these validation criteria,
the following checklist/guideline is provided for tablets and dry-filled capsules
for inclusion in an in-depth validation program. Some of these unit operations
will not be applicable for every solid dosage form (e.g., direct compression
tablets and uncoated tablets).
VII. TABLETS
A. Tablet Composition
Identify the key physicochemical properties [17–19, 45–51] of the drug substance
that need to be considered in developing the formulation, such as the
following:
Solubility of the drug substance throughout the physiological pH range:
Depending on the solubility of the drug, a surfactant may be needed to
enhance dissolution.
Particle size distribution and surface area: The particle size distribution
of the drug may determine what grade of an excipient (e.g., microcrystalline
cellulose) to use.
Morphology: If the drug is amorphous or has different polymorphs, certain
excipients may be used to prevent conversion of the drug to other physical
forms.
True and bulk density: An excipient (e.g., diluent) that has a similar bulk
density as the drug may be selected to minimize segregation, especially
with a direct compression formulation.
Copyright © 2003 Marcel Dekker, Inc.
Figure 1 Validation of new processes. (Courtesy of AstraZeneca Pharmaceuticals LP,
Wilmington, Delaware.)
Copyright © 2003 Marcel Dekker, Inc.
Figure 2 Validation of existing processes. (Courtesy of AstraZeneca Pharmaceuticals
LP, Wilmington, Delaware.)
Copyright © 2003 Marcel Dekker, Inc.
Material flow and compressibility: A free flowing, highly compressible material
such as microcrystalline cellulose may be used for drugs with poor
flow or compressibility properties.
Hygroscopicity: Special environmental working conditions may be required
to ensure that moisture is not picked up during material storage or handling
and during the manufacture of the tablet dosage form.
Melting point: If the drug has a low melting point, a direct compression
formulation may need to be developed instead of a wet granulation
formulation to avoid drying the material and potentially melting or degrading
the drug.
Provide the reason for the presence of each ingredient in the formula. Why was
a particular ingredient (e.g., povidone) used from an excipient class (e.g.,
binder)? Performance? Supply? Cost? Indicate whether a particular grade or
manufacturer is required for an ingredient and the reasons. Justify the level or
range of each ingredient, especially the binder, disintegrant, and lubricant.
Explain the required unit operations in relationship to the tablet formulation.
For example
Why was high shear wet granulation used instead of dry granulation?
Why is the tablet film coated?
B. Process Evaluation and Selection
Determine the unit operations needed to manufacture the tablets.
1. Mixing or Blending
The mixing or blending unit operation may occur once or several times during
the tablet manufacture. For example, a direct compression formulation may involve
one blending step in which the drug and the excipients are blended together
prior to compression. A wet granulation formulation may require two
mixing/blending steps: (1) prior to granulating to have a uniform drug/excipient
mixture, and (2) after milling the dried granulation to add other excipients, such
as the lubricant. Some or all the items provided in this section may therefore be
pertinent for validation, depending on the mixing or blending objective.
The following physical properties of the drug and excipients are factors
in creating a uniform mix or blend:
Bulk density
Particle shape
Particle size distribution
Surface area
Copyright © 2003 Marcel Dekker, Inc.
Materials that have similar physical properties will be easier to form a uniform
mix or blend and will not segregate as readily as materials with large differences.
Items to consider:
Mixing or blending technique: Diffusion (tumble), convection (planetary
or high intensity), or pneumatic (fluid bed) techniques can be used to
mix or blend materials. Determine the technique that is required for
the formulation or process objective. It may be different, depending on
whether you are mixing the drug and excipients for a direct compression
formulation or adding the lubricant (e.g., magnesium stearate) to
the granulation.
Mixing or blending speed: Determine the intensity (low/high shear) and/or
speed (rpm) of the mixing or blending. Mixing the drug and excipient will
require more intense mixing than adding the lubricant to the final blend.
Mixing or blending time: How much mixing or blending is required to
obtain a uniform mixture? The mixing or blending time will be dependent
on the mixing or blending technique and speed. Experiments
should be done to determine if the materials can be overmixed, resulting
in demixing or segregation of the materials. Demixing can occur due
to the physical property differences (e.g., particle size distribution and
density). For example, demixing can occur in a direct compression formulation
in which the drug substance is micronized (5 microns) and the
excipients are granular (500–1000 microns).
Drug uniformity: Content uniformity is usually performed to determine
the uniformity of drug throughout the mix or blend. Representative
samples should be taken throughout the mix or blend. The sampling
technique and handling of the materials are key in obtaining valid content
uniformity results. Segregation of the sample can occur by overhandling,
resulting in inaccurate results. For the final blend (blend prior
to compression), the sample taken should be equivalent to the weight
of a single tablet.
Excipient uniformity: Besides drug uniformity, excipients need to be uniform
in the granulation or blend. Two key excipients are:
• Lubricant: The lubricant needs to be distributed uniformly in the
mixture/granulation for the high-speed compression operation. Uneven
distribution of the lubricant can result in picking and sticky problems
during compression. It can also lead to tablet performance problems
(low dissolution due to excessive lubricant in some tablets).
• Color: The colorant(s) need(s) to be evenly distributed in the mixture
so that the tablets have a uniform appearance (e.g., color, hue, and
intensity). The coloring agent may need to be prescreened or more uni-
Copyright © 2003 Marcel Dekker, Inc.
formally dispersed in the blend prior to compression to avoid speckling
or shading of the color.
• Equipment capacity/load: The bulk density of materials or granules
will affect the capacity of the equipment. If an excipient in the formulation
affects the density of the final blend to a greater extent than any
other ingredient, then a well-controlled density specification for that
excipient may be warranted. Test different-sized loads in the mixer/
blender (e.g., 30, 50, and 70% of working volume) for optimal mixing
or blending. Undercharging or overcharging a blender can result in poor
drug or tablet lubricant distribution.
2. Wet Granulation
What type of wet granulation technique will be used? Will it be low shear (e.g.,
Hobart), high shear (e.g., Diosna, GEI-Collette) or fluid bed (e.g., Glatt, Fluid
Air)? Each technique will produce granules with different physical properties
and will require monitoring of different processing parameters.
Wet granulation parameters to be considered during development and validation
are:
Binder addition: Should the binder be added as a granulating solution or
dry like the other excipients? Adding the binder dry avoids the need to
determine the optimal binder concentration and a separate manufacture
for the binder solution.
Binder concentration: The optimal binder concentration will need to be
determined for the formulation. If the binder is to be sprayed, the binder
solution needs to be dilute enough so that it can be pumped through the
spray nozzle. It should also be sufficiently concentrated to form granules
without overwetting the materials.
Amount of binder solution/granulating solvent: How much binder or solvent
solution is required to granulate the material? Too much binder or
solvent solution will overwet the materials and prolong the drying time.
The amount of binder solution is related to the binder concentration.
Binder solution/granulating solvent addition rate: Define the rate or rate
range at which the binder solution or granulating solvent can be added
to the materials. Can the granulating solution be dumped into the mixer
or does it have to be metered in at a specific rate?
Mixing time: How long should the material be mixed to ensure proper
formation of granules? Should mixing stop after the addition of the
binder or solvent solution or should additional mixing be required?
Granulations that are not mixed long enough can form incomplete or
weak granules. These granules may have poor flow and compression
Copyright © 2003 Marcel Dekker, Inc.
properties. On the other hand, overmixing the granulation can lead to
harder granules and a lower dissolution rate.
Granulation end point: How is the granulation end point determined? Is
it determined or controlled by granulation end point equipment (e.g.,
ammeter or wattmeter)? Is it controlled by specifying critical processing
parameters? For example, a drug or excipient mixture may be granulated
by adding a predetermined amount of water (granulating solution)
at a certain rate. The granulation is completed after mixing for a set
time after the water has been added.
3. Wet Milling
Does the wet granulation need to be milled to break up the lumps and enhance
drying of the granulation? Wet granules that have a wide aggregate range can
lead to inefficient drying (long drying times and partially dried large granules
or lumps).
Factors to consider are:
1. Equipment size and capacity: The mill should be large enough to
delump the entire batch within a reasonable time period to minimize
manufacturing time and prevent the material from drying during this
operation.
2. Screen size: The screen needs to be small enough to delump the material,
but not too small to cause excessive heating of the mill, resulting
in drying of the granulation.
3. Mill speed: The speed should be sufficient to efficiently delump the
material without straining the equipment.
4. Feed rate: The feed rate of the wet granulation is interrelated to
screen size and mill size and speed.
4. Drying
The type of drying technique (e.g., tray, fluid bed, microwave) required for the
formulation needs to be determined and justified. The type of technique may
be dependent on such factors as drug or formulation properties and equipment
availability. Changing dryer techniques could affect such tablet properties as
hardness, disintegration, dissolution, and stability.
The optimal moisture content of the dried granulation needs to be determined.
High moisture content can result in (1) tablet picking or sticking to tablet
punch surfaces and (2) poor chemical stability as a result of hydrolysis. An
overdried granulation could result in poor hardness and friability. Moisture content
analysis can he performed using the conventional loss-on-drying techniques
or such state-of-the-art techniques as near infrared (NIR) spectroscopy.
Copyright © 2003 Marcel Dekker, Inc.
Parameters to consider during drying are:
Inlet/outlet temperature: The inlet temperature is the temperature of the
incoming air to the dryer, while the outlet temperature is the temperature
leaving the unit. The inlet temperature is critical to the drying efficiency
of the granulation and should be set high enough to maximize
drying without affecting the chemical/physical stability of the granulation.
The outlet temperature is an indicator of the granulation temperature
and will increase toward the inlet temperature as the moisture content
of the granulation decreases (evaporization rate).
Airflow: There should be sufficient airflow to ensure removal of moistureladen
air from the wet granulation. Insufficient airflow could prolong
drying and affect the chemical stability of the drug. Airflow and the
inlet/outlet temperature are interrelated parameters and should be considered
together.
Moisture uniformity: The moisture content could vary within the granulation.
Heat uniformity of the dryer (e.g., tray), amount of granulation per
tray, and incomplete fluidization of the bed are factors that could affect
the moisture uniformity of the granulation.
Equipment capability/capacity: The load that can be efficiently dried
within the unit needs to be known. A larger load will require more
moisture to be removed on drying and will affect the drying time. In
the case of fluid bed drying, a maximum dryer load is that load above
which the dryer will not fluidize the material.
5. Milling
The milling operation will reduce the particle size of the dried granulation. The
resultant particle size distribution will affect such material properties as flow,
compressibility, disintegration, and dissolution. An optimal particle size/size
distribution for the formulation will need to be determined.
Factors to consider in milling are:
Mill type: What mill type (e.g., impact or screen) should be used? Each
has several variants, depending on the means to reduce the particles.
The type of mill can generate a different particle size/size distribution.
Particle size testing will need to be conducted and the results examined
when substituting mill types.
Screen size: The selected screen size will affect the particle size. A smaller
screen size will produce a smaller particle size and a greater number of
fines.
Mill speed: What is the optimal mill speed? A higher mill speed will
result in a smaller particle size and possibly a wider particle size distri-
Copyright © 2003 Marcel Dekker, Inc.
bution. It can also generate more heat to the product, depending on the
screen size and feed rate, which could affect the stability of the product.
Feed rate: The feed rate is dependent on the mill capacity, screen size,
and mill speed.
6. Tablet Compression
Compression is a critical step in the production of a tablet dosage form. The
materials being compressed will need to have adequate flow and compression
properties. The material should readily flow from the hopper onto the feed frame
and into the dies. Inadequate flow can result in “rat holing” in the hopper and/
or segregation of the blend in the hopper/feed frame. This can cause tablet
weight and content uniformity problems. As for the compressibility properties
of the formulation, it should be examined on an instrumented tablet press.
Factors to consider during compression are as follows:
Tooling: The shape, size, and concavity of the tooling should be examined
based on the formulation properties and commercial specifications. For
intagliated (embossed) tablets, factors such as the position of the intagliation
on the tablet and the intagliation depth and style should be examined
to ensure that picking of the intagliation during compression or
fill-in of the intagliation during coating does not occur.
Compression speed: The formulation should be compressed at a wide
range of compression speeds to determine the operating range of the
compressor. The adequacy of the material’s flow into the dies will be
determined by examining the tablet weights. Is a force feeder required
to ensure that sufficient material is fed into the dies?
Compression/ejection force: The compression profile for the tablet formulation
will need to be determined to establish the optimal compression
force to obtain the desired tablet hardness. The particle size/size distribution
or level of lubricant may need to be adjusted in order to have a
robust process on a high-speed compressor.
The following in-process tests (as discussed in Sec. V) should be examined
during the compression stage:
Appearance
Hardness
Tablet weight
Friability
Disintegration
Weight uniformity
Copyright © 2003 Marcel Dekker, Inc.
7. Tablet Coating
Tablets may be coated for various reasons.
Stability
Taste masking
Controlled release
Product identification
Aesthetics
Safety–material handling
Tablet coating can occur by different techniques (e.g., sugar, film, or compression).
Film coating has been the most common technique over recent years
and will be the focus of this section.
Key areas to consider for tablet coating include the following:
Tablet properties: Tablet properties such as hardness, shape, and intagliation
(if required) are important to obtain a good film-coated tablet. The
tablet needs to be hard enough to withstand the coating process. If tablet
attrition occurs, the tablets will have a rough surface appearance. For
tablet shape, a round tablet will be easier to coat than tablets will multiple
sides or edges because of the uniformity of the surface. For intagliated
tablets, the intagliation style and depth should be developed to
prevent fill-in or chipping of the intagliation.
Equipment type: The type of coater will need to be selected. Conventional
or perforated pan and fluid bed coaters are potential options.
Coater load: What is the acceptable tablet load range of the equipment?
Having too large a pan load could cause attrition of the tablets because
of the overall tablet weight in the coater. In the case of a fluid bed
coater, there may not be sufficient airflow to fluidize the tablets.
Pan speed: What is the optimal pan speed? This will be interrelated to
other coating parameters, such as inlet temperature, spray rate, and flow
rate.
Spray guns: The number and types of guns should be determined in order
to efficiently coat the tablets. The spray nozzles should be sized properly
to ensure even distribution over the tablet bed and to prevent clogging
of the nozzles. The location and angle of the spray gun(s) should
be positioned to get adequate coverage. Having the guns positioned too
close together can lead to a portion of the tablets to be overwet.
Application/spray rate: The optimal application/spray rate should be determined.
Spraying too fast will cause the tablets to become overwet,
resulting in clumping of tablets and possible dissolution of the tablet
surface. Spraying too slowly will cause the coating materials to dry
Copyright © 2003 Marcel Dekker, Inc.
prior to adhesion to the tablets. This will result in a rough tablet surface
and poor coating efficiency.
Tablet flow: The flow or movement of the tablets in the coater should be
examined to ensure proper flow. There should be sufficient tablet bed
movement to ensure even distribution of the coating solution onto the
tablets. The addition of baffles may be required to provide adequate
movement of tablets for tablet coating.
Inlet/outlet temperature and airflow: These parameters are interrelated and
should be set to ensure that the atomized coating solution reaches the
tablet surface and then is quickly dried.
Coating solution: The concentration and viscosity of the coating solution
will need to be determined. The solution will need to be sufficiently
diluted in order to spray the material on the tablets. The concentration
of the coating solution will also determine the amount and volume of
solution to be applied to the tablets. The stability of the coating solution
should be investigated to establish its shelf life.
Coating weight: A minimum and maximum coating weight should be established
for the tablet. Sufficient coating material should be applied to
the tablets to provide a uniform appearance; however, it should not be
great enough to cause fill-in of the intagliation.
Residual solvent level: If solvents are used for tablet coating, the residual
solvent level will need to be determined.
Appearance testing of the tablets is critical during the coating operation.
Items to look for include the following:
Cracking or peeling of the coating
Intagliation fill-in
Surface roughness
Color uniformity
Coating efficiency should be determined for the coating operation. The efficiency
will determine the amount of coating solution overage that may be required.
C. Equipment Evaluation
In an ideal situation, the equipment used to manufacture tablet dosage forms
would be selected based on such factors as formulation, safety requirements,
handling/production efficiencies, and commercial demands. In reality, the equipment
used is usually what is already available at the development facility or
production plant. In either case, the equipment should be qualified (installation
and operation) before being used. Cleaning procedures should also be available
Copyright © 2003 Marcel Dekker, Inc.
to ensure that cross-contamination does not occur. The equipment design, operating
principles, and capacity should be investigated.
The following items should be considered when evaluating equipment for
the manufacture of the tablet dosage forms.
1. Mixer/granulator
a. What is the method of mixing (e.g., planetary, plows, choppers,
pneumatic)?
b. Is the equipment capable of providing low and/or high shear to
the material?
c. Can the mixing be varied (e.g., changing the rpm of the impeller)?
d. Does the mixer/granulator have a monitoring system (e.g., end
point detection) or can it accommodate one?
e. What is the working load range and capacity of the equipment?
f. How is material charged and discharged from the unit? Is it manual,
semiautomated, or automated?
g. Are there options to introduce the granulating fluid (e.g., dump,
meter, or spray)?
2. Blender
a. What type (i.e., geometric shape) is the blender? Is it a V blender,
double cone, cube, or bin?
b. What is the positioning of the axis rotation (e.g., horizontal,
slant)?
c. What is the working load range and capacity of the equipment?
d. What features does the equipment have for ease of handling powders,
automated charging, and discharging (e.g., Vac-U-Max, Gemco
valves)?
e. Can samples be easily taken from the unit? Can samples be taken
from more than one location?
f. Are there dead spots (inefficient mixing areas) on the unit?
g. Can the equipment be easily cleaned?
h. Can the equipment heat the powder blend if needed? What is the
heating source?
3. Dryer
a. What is the operating principle of the dryer (e.g., direct heating—
fluid bed, indirect conduction—tray, or indirect radiant—microwave)?
b. Will the wet material be static (e.g., tray) or fluid (e.g., fluid
bed)?
c. What is the working load range and capacity of the equipment?
d. What is the heating range and airflow capabilities of the equipment?
Copyright © 2003 Marcel Dekker, Inc.
e. What is the heat distribution of the unit? Are there any hot and/
or cold spots?
f. Can the unit pull a vacuum? What is the vacuum range of the
unit?
g. Can the equipment handle different types of filter bags? For example,
can a filter bag be dedicated to a particular product?
h. Does the equipment have a filter bag shaking mechanism to prevent
material from adhering to the bags? Does the shaking mechanism
have options (e.g., intermittent, continuous)?
4. Mills
a. What is the mill type (e.g., impact or screen)?
b. What is the configuration of the impact mill (e.g., hammer or pin/
disc) or screen mill (e.g., rotating impeller or screen, oscillating bar)?
c. What type or size hammers or pin/disc can be used on the unit?
d. Can the impeller (e.g., hammers) be positioned in different ways?
e. What size screens or plates can be used on the unit?
f. Is the speed on the impeller/screen variable? What is the rpm
range?
g. What is the throughput range of the unit?
h. What type of feed system is required? What feed rate can the unit
handle?
i. Can the unit wet- and/or dry-mill materials?
j. Does the unit generate a significant amount of heat, possibly affecting
the product?
k. Is the unit portable?
5. Tablet compressor
a. How many compression stations does the compressor have?
b. What is the operating range (rpm) of the unit?
c. What is the output range of the compressor (e.g., tablets per min)?
Will the unit meet the demands (sales forecast) for the product?
d. What kind of powder feeding capabilities does the equipment
have (e.g., gravity, power-assisted, or centrifugal)? Can this capability
be altered or controlled (e.g., open feed frame, forced below
feeder)?
e. What is the compression force range of the equipment? Some
products, especially large tablets or slugs, require a significant
compression force (greater than 5 to 25 kN).
f. Is the equipment capable of monitoring compression and ejection
force?
g. Does the unit have precompression capabilities?
h. How long can the equipment operate without routine maintenance?
This is related to air drag-off from the compression table,
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compression rolls and ejection cams, and the lubrication system
(oil misting).
i. How long is the turnaround time for complete cleaning? One
shift? Two shifts? This downtime can be significant and may affect
the need for a multishift tableting operation or numerous tablet
machines.
j. Does the equipment possess automated weight control capability
(e.g., Thomas’s Sentinel device)?
k. Does the equipment require specialized tooling, or can the equipment
use tooling from other equipment (e.g., length of punch
shafts, diameter of dies)?
l. Can the equipment perform a specialized function in addition to
basic tablet compression (e.g., multilayer tablet compression, compression
coating)?
m. Is the unit capable of being contained to protect the operator and
environment?
6. Tablet Coater
a. What is the coater type (e.g., pan or fluid bed)?
b. Is the pan perforated?
c. Can the coater accommodate different size pans?
d. What is the working capacity range of the coater (i.e., pan load)?
e. Does the pan coater have a “variable drive” capability? This may
be needed to achieve proper tablet mixing in the pan so that the
coating solution is applied uniformly to the tablets.
f. Can the angle of the pan’s pitch be varied?
g. What kind of air input (volume and temperature) and vacuum
drag-off is required for optimal operation of the coater? These
utility requirements may exceed the capacities available in the
plant.
h. What type of spray system can be used with the equipment?
i. What is the shape of the coating pan (e.g., oval, mushroom,
round)? The shape characteristic will affect the degree of agitation
and the direction of tablet flow in the pan. The spray nozzle
configuration will have to be designed to ensure adequate spray
coverage over the tablet bed.
j. Is it possible to utilize the equipment for sugar coating as well as
film coating? Certainly, if this were possible, capital expenditures
would be reduced.
k. Is it possible to modify the pan with the installation of baffles?
Baffles may be needed to ensure good tablet movement in the
pan.
l. Can various solvents (ethanol) be used in the equipment?
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m. Does the equipment require a specialized room condition (e.g.,
being explosion-proof)?
VIII. HARD GELATIN CAPSULES
Many of properties and processes for hard gelatin capsules [19,48] are the same
as with tablet dosage forms. Instead of covering these items again, only items
that are unique to hard gelatin capsules will be discussed in this section.
A. Capsule Composition
The composition of the capsule contents would be similar to that presented in
the tablet composition section. The capsule shell and the interactions of the shell
and the contents will be discussed further.
1. Capsule Shell
Provide the reason for the presence of each ingredient in the capsule formula.
Justify the level and grade of each ingredient.
Explain the selection of the capsule size and shape.
Discuss the need for capsule identification (e.g., color or imprinting).
2. Capsule Shell Contents
Establish the compatibility of the capsule shell and the capsule contents.
Determine the hygroscopic nature of the capsule formulation. For example,
a hygroscopic formulation (active ingredient and/or excipients) can
pull water from the capsule shell, which could affect the
Active ingredient—stability issues such as degradation and morphology
changes
Formulation—hardening on the materials, resulting in a decreased
dissolution rate
Capsule shell—more brittle
B. Process Evaluation and Selection
The process to manufacture the contents of a hard gelatin capsule is the same
as a tablet. It may required only a blending step, such as a direct compression
tablet, or several unit operations, such as a wet granulation tablet (e.g., mixing,
wet milling, drying, dry milling, and blending). In either case, the materials are
then encapsulated in a capsule shell.
Copyright © 2003 Marcel Dekker, Inc.
C. Encapsulation
Encapsulation is a critical step in the production of capsules, similar to the
compression step for tablet dosage forms. The materials to be encapsulated will
need to have good flow properties and a consistent density. The materials may
also need to be compressible in order to be dosed into the capsules; however,
they should also be easily deaggregated so not to adversely affect the dissolution
of the drug.
Factors to consider during encapsulation are:
Encapsulation type: The type of encapsulation technique (e.g., auger, vacuum,
dosator) required for the formulation needs to be determined and
justified. Examples are
Auger: Capsugel Type B or Elanco No. 8
Vacuum: Perry
Vibratory: Osaka
Dosing disk: H&K
Dosator: MG2 or Zanasi
The type of technique may be dependent on such factors as drug or formulation
properties and equipment availability.
Encapsulation speed: The formulation should be encapsulated at a wide
range of speeds to determine the operating range of the encapsulator.
By examining the capsule weights, the adequacy of the material’s flow
will be determined.
The following in-process tests (as discussed in Sec. V) should be examined
during the encapsulation step:
Appearance
Capsule weight
Disintegration
Weight uniformity
D. Equipment Evaluation
1. Encapsulator
1. What is the encapsulation mechanism (e.g., auger, dosing disk, dosator)?
2. How many encapsulation stations does the encapsulator have?
3. What is the operating range of the unit?
4. What is the output range of the encapsulator (i.e., capsules per min)?
Will the unit meet the demands (sales forecast) for the product?
5. What kind of powder feeding capabilities does the equipment have
Copyright © 2003 Marcel Dekker, Inc.
(e.g., gravity- or power-assisted)? Can this capability be altered or
controlled?
6. How long can the equipment operate without routine maintenance?
7. How long is the turnaround time for complete cleaning? This downtime
can be significant and may affect the need for a multishift operation
or additional machines.
8. Does the equipment possess automated weight control capability?
9. Can the equipment perform a specialized function in addition to basic
encapsulation (e.g., tablet in capsules with excipient backfill)?
10. Is the unit capable of being contained to protect the operator and
environment?
IX. OUTSOURCING IMPLICATIONS ON VALIDATION
In recent years, outsourcing, in response to financial and time-to-market pressures,
has greatly increased within the pharmaceutical industry. Today, third
party providers are being used at a rate of 40–50% to supplement internal R&D,
manufacturing, and sales and marketing activities. While the majority of outsourcing
remains tactical (transactional), there is an increasing movement to
strategic outsourcing characterized by partnerships and alliance relationships.
The use of third party suppliers does not absolve the pioneer pharmaceutical
firm from ensuring that validation is conducted in a scientific and comprehensive
manner. The FDA and other regulatory bodies will hold the pioneer
company fully responsible for validation, as it—validation—is the foundation
for all information and data being generated to support new drug applications.
As part of the due diligence process, therefore, clients must ensure that suppliers
have validation procedures and practices in place. Once a supplier is chosen and
work commences, the client must include validation auditing as part of the ongoing
relationship monitoring to ensure that it is being successfully practiced.
Analytical testing (preformulation, stability, product release) is a core
component of pharmaceutical operations from early R&D through manufacturing
of the commercial product. The original analytical methods are usually developed
by the pioneer pharmaceutical firm and transferred to the provider. In
some cases, the early methods are only preliminary methods and are not sufficiently
robust to test the quality of downstream (clinical, commercial, and line
extension) products and facility quality practices (cleaning validation). In those
situations, the supplier is often asked to develop new methods, and in some
cases those methods are transferred back to the client. In either scenario, the
transfer of validated analytical methodology consists of the following four main
tasks [52]:
Copyright © 2003 Marcel Dekker, Inc.
1. Training of the contract analysts by the client R&D group
2. Agreeing on an interlaboratory qualification protocol
3. Cross-validating the analytical method by simultaneous testing at both
sites
4. Statistically comparing the data generated by both sites and qualification
by quality assurance (QA)
In recent years, the International Conference on Harmonization (ICH) has
published two documents that serve as expert guidance on analytical and related
validation [53,54]. As part of the outsourcing process, the client and provider
should review these and related regulatory guidances (e.g., cleaning validation)
to ensure that there is a mutual understanding and agreement on the scientific
basis of methods validation.
X. CONCLUSIONS
The guidelines contained within this chapter should be considered as part of
a comprehensive validation program for solid oral dosage forms. The unique
formulation or process characteristics of a particular product and the equipment
available to manufacture that product may dictate the need for a specialized
validation program. As such, the multidisciplinary validation team must identify
the product and process characteristics that must be studied and incorporate
specific validation tests to ensure that that product will meet all quality, manufacturing,
and regulatory requirements.
Solid dosage form validation should be part of a comprehensive validation
program within a company. The total program should begin with validation of
the active pharmaceutical ingredient (API) characteristics so that this material
will be uniform batch after batch, providing a solid footing upon which the
dosage form will be built. A raw material evaluation committee, comprising
personnel from formulation, analytical and process development, quality control,
and purchasing, should determine the extent to which a new or alternate material
must be evaluated before it can be considered acceptable for routine use.
Analytical methods validation is a critical component of the entire company
validation program. A method is not declared acceptable until a collaborative
crossover study is conducted between two development laboratories and at
least one quality control laboratory to ensure proper precision, accuracy, and
efficiency. In the new world of outsourcing, it is imperative that an analytical
crossover study be conducted between the client and supplier before any work
is begun on dosage form development.
Validation of a new or existing product involves the efforts of scientists
at various stages of the product development life cycle. Scientific information
Copyright © 2003 Marcel Dekker, Inc.
obtained during the preformulation stage can form the basis for a well-designed
and comprehensive validation program. As development proceeds, validation
considerations are broadened to ensure that critical formulation, analytical, and
process factors are integrated into the overall validation program. The parameters
chosen must be relevant indicators of a controlled process. It is not sufficient
merely to devise a test and set specifications for it; rather, it is desirable
to show a cause and effect relationship between the parameter tested and control
of the quality and/or process output.
While validation as a discipline is widely known across the pharmaceutical
industry, there are still a significant number of instances in which preapproval
inspection results or product recalls identify an insufficient validation program as
the root cause of the difficulty. Continued awareness of validation requirements
and a diligent application of validation principles will thus help to ensure that
pharmaceutical products will be able to be developed and produced with the quality
and reproducibility required from regulatory agencies across the world.
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6
Validation for Medical Devices
Toshiaki Nishihata
Santen Pharmaceutical Co., Ltd., Osaka, Japan
I. MEDICAL DEVICES AND CATEGORIES
In general, a medical device is defined as follows: a medical device is an implant
and equipment to be used either to achieve disease diagnosis, medical
treatment, or disease prevention for human and animals, or to influence the
physical structure and function of human and animals. Medical devices for humans
may also be classified based on whether and how long the device is in
contact with tissue or cells and on the degree of disjunction induced by the
device when in a disabling situation. The term covers various categories, such
as scissors and tweezers, with small risk to human function, to central venous
catheters, artificial dialysis (human kidney), and pacemakers, with high risk to
human function.
The ISO (International Standards Organization) standard (ISO 13485 [1])
for medical devices, Quality Assurance System for Medical Devices, has been
implemented globally. GMPs are clearly required for the manufacture of medical
devices, including process control, quality control, and appropriate facilities
and equipment. GMP also plays a role in maintaining the quality of medical
devices. Performing only a specification test of the final product for release may
not guarantee high quality of the device; design qualification/verification in the
development step must be done in detail and process control by scientific parameters
is important to assure quality. Because the term medical device covers a
variety of categories, it may be difficult to establish a simple quality control
system. To achieve appropriate quality control status, medical devices may be
categorized under design, manufacturing method, assembly method, and quality
control testing, as shown in Table 1.
The medical devices in category 1 in Table 1 are controlled during in-
Copyright © 2003 Marcel Dekker, Inc.
Table 1 Categories of Medical Devices Based on Their Design, Manufacturing
Method, Assembly Method, and Quality Control Testing
Category 1: Medical devices that are controlled by in-process tests, with critical specifications
designed for both individual products and a group, but not implemented in
human and animals.
Category 2: Medical devices that are composed in batches and are tested with representatives
in a batch.
Category 3: Medical devices that are controlled with each component (part) for assembly
in the manufacturing process, and constituted (assembled) and maintained at the user
site. Of course, the function of the medical device after assembly must be tested before
release.
Category 4: Medical devices that are controlled by in-process tests, with critical specifications
designed for both individual products or a group, and are implemented in
human and animals for the long term.
process testing with critical specifications designed either for individual products
or a group of products. Qualification of equipment to test critical product
specifications and validation of test methods should be key factors. In this category,
scissors, tweezers, and a pair of glasses are involved.
The medical devices for category 2 in Table 1 are composed in batch.
Process validation should be a key factor in manufacturing uniform products. In
this category, sterile products, such as central venous catheters and ophthalmic
viscosurgical solution without pharmacological and metabolic action, are involved.
In vitro diagnostic products are also involved in this category.
The medical devices for category 3 in Table 1 are constituted (assembled)
at the user site. Method verification for constitution should be one of the key
factors, as well as qualification and validation in the manufacture of components
(parts). Nuclear magnetic resonance spectroscopy (NMR) is included in this
category.
The medical devices in category 4 of Table 1 are controlled in-process
testing with critical specifications designed for individual products or a group
of products and are implanted. The compatibility of product materials with tissue
and cells, the stability of product in the implanted site, and the sterility of
product should be key factors to assure the product safety. Intraocular lenses
and pacemakers are included in this category.
Because a qualified method for the manufacture and implementation of
medical devices may be more variable in comparison to pharmaceutical dosage
forms, it may be necessary to make clear what is (are) critical factor(s) for each
device during the validation of the manufacturing process. The validation
method for the medical device in each category will thus be described later.
Copyright © 2003 Marcel Dekker, Inc.
Since the definition of validation seems to vary from nation to nation, we
will include all activities from design to final product, as well as individual
validation, such as process validation [2] (product qualification in ISO).
II. PRODUCT SPECIFICATION FILES AND MEDICAL
DEVICE VALIDATION IN QUALITY SYSTEMS
Establishing a quality system is required for manufacturing medical devices.
The International Standards Organization [3], CFR (Code of Federal Regulations)
21 section 820 [4] for FDA, and the GHTF (Global Harmonization Task
Force) [5] for medical devices are descriptive of quality systems, as shown in
Table 2. Because ISO is a global organization and key player in EU market
integration, GHTF was formed in 1992 in an effort to harmonize global regulatory
requirements for the medical device industry by incorporating ISO standards.
Furthermore, ISO has been incorporated with ANSI (American National
Standards Institute), thus there are no critical differences in quality systems and
validation among CFR, ISO, and GHTF. The quality system is also a key issue
in achieving appropriate validation for the manufacture and quality control of
medical devices. Although this section describes the validation of medical devices,
it should be understood that validation is also required to achieve appropriate
quality systems.
Just as preparing “product specification files” or “product justification
files” may be recommended for medicine, preparing a “medical device specification
file” may be recommended to achieve appropriate overall validation in a
Table 2 Requirements of Quality System for Medical Devices
1. ISO/DIS 13485: The supplier shall establish, document, and maintain a quality system
as a means of ensuring that product conforms to specified requirement. The
supplier shall prepare a quality manual covering the requirements of ISO 9001. The
quality manual shall include or make reference to the quality system procedures and
outline the structure of the documentation used in the quality system.
2. CFR21 Section 820.5 Quality System: Each manufacturer shall establish and maintain
a quality system that is appropriate for the specific medical device(s) designed
or manufactured, and that meets requirements of this section.
3. Global Harmonization Task Force (GHTF), which was formed to harmonize regulatory
requirements for the medical device may recommend referring to ISO 10013
for general guidance on the content of a quality manual.
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quality system. Medical device specification files may include items described
in Table 3.
The specification file may also include the development history of the
product and process for manufacturing; that is, the rationale of product design
and manufacturing process development are critical to assure the quality of
product. The rationale for establishing the product design and manufacturing
process includes the influence of the design variation on the product function
and its specifications. Product function is defined as the scope and potency of
disease diagnosis, medical treatment, or disease prevention with the product.
Design variation, defined as an acceptance range, includes the specification
range of raw materials and in-process products and the operation range of manufacturing
process equipment; that is, the acceptance range of variation factors
to assure that identical products are manufactured.
III. REGULATORY REQUIREMENTS OF VALIDATION FOR
MEDICAL DEVICES
Validation includes the design concept (design of product developed), design
verification, each qualification for manufacturing, and assay/test equipment, including
the establishment of a maintenance program, the development stage of
manufacturing operation conditions and test methods, and individual validation
(process validation and analytical method validation). Validation is thus required
to ensure the establishment of product specifications, how the manufacturer
maintains the quality of a product in the manufacturing process, and what factors
are critical in assuring the proper functioning of the medical device. To
Table 3 Items Included in the Medical Device Specification File to Achieve Validation
1. Design concept, design established for product, and design verification with product
specification proposed.
2. Specification for raw materials, intermediate, labels, packaging materials, and finished
products
3. Standard operating procedures (SOPs) for equipment operation, including maintenance,
production methods, and utility and environmental specification
4. Process validation protocol and records
5. Inspection/test procedures for in-process control, product specification, and acceptance
criteria
6. Sterilization process protocol and record (when needed)
7. Standard operating procedures (SOP) for assembly and servicing (including maintenance)
procedures (when needed)
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achieve the appropriate quality maintenance of the products manufactured, the
manufacturer shall maintain GMP conditions in the written standard operation
procedures (SOPs), including the maintenance program (CFR21 section 821.61
in the United States). CFR21 sections 820.72 and 820.75 state the requirements
listed in Table 4, which are also required in ISO 9001 (section 4.11).
To control the manufacturing procedure adequately and to confirm the
specifications of the in-process product or the final product, the manufacturing
machines and measurement equipment shall be maintained to work accurately
and consistently. Since accurate inspection ensures the results of test items measured
by the intended equipment, the method for inspection shall always be
carried out in the same manner. To ensure consistent inspection, the documented
procedure shall be maintained, both with accurate inspection records and verification
of the records. (See Table 4.)
Table 4 CFR21 Section 820.72 Requirements
CFR21 Section 820.72 Inspection, measuring, and test equipment
820.72(a) Control of inspection, measuring, and test equipment
Each manufacturer shall ensure that all inspection, measuring, and test equipment,
including mechanical, automated, or electronic inspection and test equipment, is suitable
for its intended purposes and is capable of producing valid results.
1. Each manufacturer shall establish and maintain procedures to ensure that equipment
is routinely calibrated, inspected, checked, and maintained.
2. The procedures shall include provisions for handling, preservation, and storage of
equipment, so that its accuracy and fitness for use are maintained.
3. These activities shall be documented.
820.72(b) Calibration
Calibration procedures shall include specific directions and limits for accuracy and
precision. When accuracy and precision limits are not met, there shall be provisions for
remedial action to re-establish the limits and to evaluate whether there was any adverse
effect on the device’s quality. These activities shall be documented.
(1) Calibration standard: Calibration standards used for inspection, measuring, and test
equipment shall be traceable to national or international standards.
1. If national or international standards are not practical or available, the manufacturer
shall use an independent reproducible standard.
2. If no applicable standard exists, the manufacturer shall establish and maintain
an in-house standard.
(2) Calibration records: The equipment identification, calibration dates, the individual
performing each calibration, and the next calibration date shall be documented. These
records shall be displayed on or near each piece of equipment or shall be readily available
to the personnel using such equipment and to the individuals responsible for calibrating
the equipment.
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Accurate calibration of the equipment is critical to assure the manufacture
of identical products. To achieve accurate calibration and to maintain the calibration
adequately, periodic review of the method may be necessary based on
the performance records and deviation records, as described in Table 4.
Classic quality control methods normally focus on specification testing of
the final product. There may be some concern about controlling the products
only with the specification testing of final products (i.e., it should also be required
to incorporate the in-process control parameters, such as the specification
of starting material and operation condition of equipment for manufacture).
These concerns include the following:
1. Whether or not the specification of the final product has been established
based on its functional efficacy and safety. For example, the
establishment of the specification for each item (e.g., the size of each
dimension of the product and the materials used for the product)
should be justified by incorporating stability information.
2. There may be more than one manufacturing method used to obtain the
final product with the same specification testing results. The products
manufactured in a “different” method may be similar but not always
equivalent, even with satisfaction of the specification of the final
product, when the specification of the final product is not established
by incorporating manufacturing procedures and starting material specifications.
The different manufacturing method may include a change
in operational conditions, such as operation time, and a change of
manufacturing site. The critical issue for process validation is how to
develop the appropriate manufacturing procedure and in-process control
methods scientifically and to establish the acceptance criteria.
3. According to GMP compliance, the product shall be manufactured according
to the direction of the given “master record.” When deviation
occurs, the acceptance criteria for the deviation may be obtained during
the development stage of the manufacturing procedure; that is, although
the master record gives only very limited operational conditions based
on the functioning of the manufacturing equipment according to GMP
requirements, the scientific data obtained in the development stage (efficiency
trials described later) help to establish acceptance criteria that
are broader in scope than the directions given in the master record.
4. Process validation shall be performed according to the master record
and shall be evaluated according to the specification testing given in
the GMP requirements. Essential factors, including the operational
conditions of the manufacturing procedure and the “end point” of
each step of the manufacturing procedure, should be established prior
to process validation.
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As shown in Table 5, where the results of a process cannot be fully verified
by subsequent inspection and testing the process shall be validated. The
process validation is required to assure that each process produces identical inprocess
product and to identify the final product by assuring that all processes
are carried out in the same manner.
As described in Table 5, each manufacturer shall then establish and maintain
procedures for monitoring and controlling process parameters for validated
processes. To ensure that each manufacturing condition is maintained adequately,
it is necessary to ensure the control parameters of the operating machinery.
The control parameters should include the operation speed, operation pressure,
operation temperature, and electrical current of the machinery during
operation.
The acceptance criteria to manufacture product with identical quality shall
be established scientifically. When change or deviation for the process occurs,
Table 5 CFR21 Section 820.75 Requirements
CFR21 Section 820.75 Process Validation
820.75(a)
1. Where the results of a process cannot be fully verified by subsequent inspection and
tests, the process shall be validated with a high degree of assurance and approved
according to established procedures. The validation activities and results, including
the date and signature of the individual(s) approving the validation and where appropriate
the major equipment validated, shall be documented.
2. Examples of such processes include sterilization, aseptic processing, injection molding,
and welding. The validation method must ensure that predetermined specifications
are consistently met.
820.75(b)
Each manufacturer shall establish and maintain procedures for monitoring and control
of process parameters for validated processes to ensure the specified requirements continue
to be met.
(1) Each manufacturer shall ensure the validated processes are performed by qualified
individual(s).
(2) For validated processes, the monitoring and control methods and data, the date
performed, and, where appropriate, the individual(s) performing the process or the
major equipment used shall be documented.
820.75(c)
When a change or process deviation occurs, the manufacturer shall review and evaluate
the process and perform revalidation where appropriate. These activities shall be
documented.
Copyright © 2003 Marcel Dekker, Inc.
the manufacturer shall review and evaluate the process and performrevalidation,
as described in Table 5.
IV. VALIDATION FOR MEDICAL DEVICES
Validation is one method of assuring that the product manufactured satisfies the
design required, the specification established, and the reproducibility of the results.
Validation may include the items described in Figure 1, although individual
validation may include IQ, OQ, process validation, and analytical validation.
Items described in the Figure 1 can be described as follows:
1. Development of the (design) concept, which is for both the product
and the manufacturing (assembly) process and test method. The design
concept for the product should include factors of function as well
as safety factors. The design concept for the manufacturing (assembly)
process and test method should include accuracy for manufacture
and testing, and safety for preventing contamination, such as occurs
from micro-organisms.
2. Preparation of design, which is for both product and the manufacturing
(assembly) process and test method. Design preparation should
satisfy the design concept.
3. Design verification, which is for both the product and the manufacturing
(assembly) process. Design verification should reflect the design
preparation.
4. Preparation of equipment for manufacture and testing, which is performed
when new equipment is necessary.
5. Installation qualification (or verification with the existing line) for
each processing machine, and assembly according to the processing
line. Installation qualification is required to confirm that all machines
and equipment are installed with all functional parts at the specific
sites intended. Preventive and corrective maintenance programs
should be established.
6. Operational qualification (or verification with the existing line) for
each processing machine and assembled processing line. Operational
qualification is required to confirm that all machines and equipment
can be operated in the designed manner within the intended range.
Preventive and corrective maintenance programs are established.
7. Efficiency trials, which means developing specific operational conditions
of the machinery and equipment in the assembled process line
to manufacture the intended product. When needed, process control
parameters for monitoring and acceptance criteria must be developed.
Copyright © 2003 Marcel Dekker, Inc.
Figure 1 Items required for validation of medical devices. Although validation should
include items 1 to 9, items 1, 2, 4, and 7 are considered to be development items.
Copyright © 2003 Marcel Dekker, Inc.
Operational conditions and the end point must be developed to satisfy
the approved specification of the products. To satisfy the developed
operational conditions and end point, master records for the products
and SOPs relating to processing must be developed and established
with appropriate approval. The end point of this stage must be reached
by establishing a master record (manufacture and specification test
methods) and by producing products that satisfy the approved specification.
8. Performance qualification, which includes the equipment qualification
operated under loaded conditions. Performance qualification is carried
out with individual equipment based on the information obtained in
efficiency trials prior to process validation under the complete assembled
condition. In the case of environmental qualification and utility
qualification, performance qualification is generally carried out under
the operating condition for 1 year to confirm there is no deviation by
season.
9. Process validation (product qualification), which is performed on each
intended product, even when manufactured in the same manufacturing
line. According to the master record, the manufacturing must be carried
out, in-process control parameters must be monitored, and specification
testing of the product must be performed. The result of specification
testing must satisfy the requirements.
Validation should include verification, qualification, individual validation
(process validation, computer validation, cleaning validation, analytical validation),
and development stage as efficiency trials (for the establishment of processing
conditions and for in-process parameters) to manufacture the intended
products. Verification, qualification, and individual validation should be achieved
in the protocol that includes the established method and acceptance criteria.
Validation is thus classified in two categories: the development stage (rectangle)
and the establishment stage (oval) based on the method shown in Figure 1.
The establishment stage includes verification, qualification, and individual
validation, including process validation, computer validation, method validation,
and cleaning validation. These establishment stage steps shall satisfy the principal
requirements in Table 6.
In practical terms, the verification, qualification, analytical validation,
cleaning validation, and process validation need to satisfy certain requirements.
1. The protocol must include the clarified purpose of each item, such
as design verification and installation qualification. For example, the
purpose of cleaning validation is to avoid any contamination.
2. The protocol shall include the established methods to perform the
study and also include the acceptance criteria for the operational pa-
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Table 6 Principal Requirements for the Establishment Stage
1. To achieve appropriate verification, qualification, and individual validation, the
method to perform shall be established and the acceptance criteria shall be clarified
in the document.
2. SOPs relating to works shall exist.
3. Studies in the establishment stage shall be performed completely according to the
method established and SOPs, and the results obtained shall satisfy the acceptance
criteria required in the document.
rameters (temperature, electrical current, etc.) of the equipment and
in-process product specifications as well as the product specifications.
When the protocol does not include the fixed operating conditions
with the acceptance criteria, the study is categorized in the development
stage rather than the qualification stage.
3. The study shall be carried out according to the method described in
the protocol. When the method used in the study deviates from the
protocol, it shall be shown that the method used is equivalent to the
method in the protocol.
4. All operating conditions and in-process parameters must be recorded.
5. The quality control testing of the final product must be performed and
the results must be recorded.
6. The results obtained shall satisfy the criteria of the operating parameters
and the specifications of the in-process products as well as the
final product.
7. The written study report shall be prepared.
8. The documents shall be verified, approved, and filed; the necessary
documents are protocol, records for operation, in-process control parameters,
specification test as quality control, and final report.
Studying the development stage works (design steps and efficiency trials
steps) is necessary for designing the product; for designing the processing line of
the product and the assembly flow of the product; for determining the processing
conditions, including the end point of each processing step; for determining the
assembly method; for determining product specification; for determining the
product specification test method; and for establishing SOPs. Development stage
works must satisfy the following:
1. The protocol must include the product concept as well as the purpose.
The product concept must be comprehensively simplified for
designing the next step and should describe the effective role of the
Copyright © 2003 Marcel Dekker, Inc.
medical device against the disease. For example, when developing
daily soft contact lenses, recovery of eyesight, cleanliness of the eye
by using disposable lenses, and low cost to satisfy disposability are
included in the product concept.
2. The protocol must include development of the design of in-process
product as well as the design of final product based on the product
concept. A program should thus be included to confirm that the design
of the product satisfies the product concept. This program will
be performed by using a checklist that includes the items for the
product concept, such as the size, shape, and nature of the materials.
3. The protocol must include the proposed tentative specifications of
the in-process product with the acceptance criteria and directs the
finalization of the specification at the end of the development stage.
The specification should be proposed based upon the product design;
that is, the specification includes the size, shape, impurities, and nature
of the materials, such as viscosity and tension. Developing the
specifications of the final product and parts for assembly must be
performed to specify the product efficacy and product liability based
on the design concept and scientific data, such as stability data.
4. The protocol must include the proposed tentative manufacturing procedure
that will be fixed at the end of the development stage. The
tentative manufacturing procedure includes what kind of manufacturing
equipment will be used, how the manufacturing equipment
will be assembled, and how to operate the equipment. The operational
condition of the equipment will be fixed at the end of the
development stage.
5. The protocol must include directions on selecting or developing the
maintenance program, including preventive and corrective action.
The maintenance program includes the calibration program of measurement
equipment and the replacement of equipment parts.
6. The study shall be carried out according to the method described in
the protocol. When the method used in the study is changed from
the protocol, it shall be justified in the document according to the
established change control system. In general, however, the acceptance
criteria of the specifications for the final product should not
be changed without specific data relating to safety and functional
assessment.
7. All operating conditions and in-process parameters must be recorded.
This is important to provide the scientific and/or statistic rationale to
fix the operating conditions at the end of the development stage.
8. The specification testing of products that are manufactured in the
trial run and stored according to the proposed conditions must be
Copyright © 2003 Marcel Dekker, Inc.
documented, because all information is necessary to finalize the
specification of the products.
9. The results obtained for the specification testing shall satisfy the
acceptance criteria that assure the efficacy and safety of the product.
10. The study report shall be prepared as “development of product” in a
written document.
11. The documents shall be verified, approved, and filed; essential documents
are the protocol, records for operation, in-process control parameters,
change control document, specification test as quality control,
and final report.
V. APPROACHES FOR VERIFICATION, QUALIFICATION,
AND PROCESS VALIDATION FOR MEDICAL DEVICES
In the beginning it should be clear what the key issues are for verification,
qualification, and process validation. Such issues are listed in Table 7.
Validation in quality systems includes establishment of procedures on how
to qualify the equipment and machinery, how to verify the design of products,
how to verify the process designed, how to verify the achievement of production
procedures, how to validate the process developed, and how to validate the
methods for measurement and assay. Validation also requires verification of
specifications or acceptance criteria of in-process parameters relating to both
raw materials and intermediate (in-process product) and finished products, and
verification of acceptance criteria for in-process parameters relating to operating
conditions of machinery and equipment. Further, when the medical device is
assembled at the user’s site, validation includes establishing procedures of how
to verify assembly.
Preparing a master project plan is useful to achieve appropriate verification,
qualification, and individual validation. According to the directions of the
master project plan, protocol is generated, the study or test is performed, and
the report is prepared. Of course, each protocol, performance record, and report
must be reviewed and approved appropriately. The master project plan may
Table 7 Key Issues for Qualification, Verification, and Individual Validation
Acceptance criteria must be key to achieve appropriate qualification, verification, and
individual validation. Acceptance criteria may be consist of various specifications of
intermediate and finished products for medical devices. Acceptance criteria also may
control parameters for operation of processing equipment and utilities used.
Copyright © 2003 Marcel Dekker, Inc.
include the items described in Table 8, section 1. The protocol required in the
master project plan includes the items described in Table 8, section 2.
The object (item a) in the master project plan provides the purpose of the
project, including the event achieved and the role of the project plan. The scope
(item a) provides the applied items, including the product, facility, and equipment
for manufacture, and the manufacturing process, including the sterilization
process when needed, the measurement equipment, and/or the test method. Item
b requires who is in charge of each item and what kind of role he or she has.
In item c, the expected events in Figure 1 and the definition of each event are
described. Design verification of product, for example, requires a comparison
of the document for the product design concept with the design drawing/formulation
of the product. It also requires recording the document number for the
product design concept and the design drawing/formulation. Criteria (item d)
include the necessity of each event, such as verification, qualification, and validation.
The criteria also include the method of creating the acceptance criteria.
Acceptance criteria may sometimes be described in the protocol, because the
Table 8 Items Included and Protocol Indicated in the Master Project Plan
1. Items included in the master project plan
a. Object and scope
b. Responsibility for project
c. Content and type of qualification, verification, or validation
d. Criteria for qualification, verfication, or validation
e. Protocol required in the project
f. SOPs that must be developed and established
g. Maintenance program (preventive and corrective)
h. Estimated period for achievement
i. Compliance
j. Change control
k. Approval
2. Protocol indicated in the master project plan
a. Verification of design
b. Installation qualification and operational qualification
c. Development of procedure, measurement, or assay
d. Performance qualification
e. Process validation
f. Measurement validation and verification
g. Assay validation
h. Verification of specification established
i. Generation and verification of assemble procedure at user’s site
Copyright © 2003 Marcel Dekker, Inc.
project plan for a new product may be prepared prior to the completion of
design verification. The criteria are important to complete risk assessments. The
project plan should describe what kind of protocol is required to complete the
project plan. The protocol (item e) required in the validation is described in
Table 8, section 2. Item f in Table 8, section 1 expects that SOPs will be established
to manufacture products. The maintenance program (item g) is required
to keep the quality of the product manufactured by maintaining the equipment
for manufacture and measurement. Item h indicates the estimated project duration
with the starting date and the target date for completion. Item i indicates
how all documents are reviewed and revised. The change control (item 10) is
necessary to perform an appropriate change of method and the acceptance criteria
for each event. The change control requires that the change should be carried
out in the established system. Item k indicates that all actions and documents
must be approved.
The protocol shall include adequate content in the same manner as the
master project plan described in Table 8, section 1. The methods used should
be described in detail. The content of the protocol leads us to perform the essential
items completely and evaluate the items scientifically and statistically.
VI. AN APPROACH TO THE VALIDATION OF MEDICAL
DEVICES AND CRITICAL ISSUES IN EACH STEP
OF THE PROCESS
Validation of the medical device is generally developed according to the steps
shown in Figure 2.
1. A critical issue in the development stage in step 1 is that the concept
of the product developed should satisfy functional and safety aspects
to achieve the expected treatment effectively. When the concept is
developed, it must be reviewed based upon risk assessment. One of
important issues in step 1 is to establish whether the device will be
sterile or not.
2. A critical issue in the design of the product in step 2 is that the design
must satisfy the concepts for the product being developed. Physical
and chemical designs of the product are developed by means of drawings
and materials used to display the function of the product, and
the tentative specification of the designed product is developed. The
chemical design should include the materials used and formulation
compositions when mixed, and reflect the biocompatibility when the
product is in the plant. The specification developed must be based on
the function designed and other physicochemical properties. The de-
Copyright © 2003 Marcel Dekker, Inc.
Figure 2 Items required for overall validation. Although validation is required for all
items, items 1, 2, 4, and 6 are considered to be development items.
Copyright © 2003 Marcel Dekker, Inc.
sign thus should include drawings of the product, its acceptance
range, and the material to be used and its specifications. When products
need to be supplied as sterile products or are to be used after
sterilization, the selection of the material and sterilization methods are
included; that is, the selection of the sterilization method should be
carried out based on maintaining chemical and physical stability of
the materials. It is also important to clarify whether the use of a terminal
sterilization method is acceptable or not. When the terminal sterilization
method is not acceptable because of low resistance of the materials
to the heat or other sterilization method, aseptic processing
should be designed. Further, elements of the sterilization method (e.g.,
equipment, operating temperature, operating pressure, and operating
time) should be described in detail for the user when the product is
required to be sterilized prior to use in the user site.
3. The critical issue in design verification in step 3 (verification stage)
is that the protocol must include both the established method to verify
and the acceptance criteria. The established method in this step may
be an evaluation checklist that includes the essential items based on
the concept, such as shape, size, and materials. For example, in the
case of the development of hydrophilic interlobular lenses (IOL), the
checklist includes biocompatible materials with polymer mixture
compositions for hydrophilic nature and the kind of diopter developed.
The selection of the polymer mixture should also be considered
in the molding method. The critical issue for acceptance criteria in
the protocol is that the specification satisfies the function, such as
diopter for IOL, and the safety of the product designed, such as the
biocompatibility of IOL material. The acceptance criteria are established
based on the acceptance range of drawings and material specifications.
The verification of the applied sterilization process is also
carried out based on the scientific evidence with no decay of materials
by sterilization. For example, because the biocompatible materials for
IOL may not be stable against the terminal heat sterilization, it should
be verified that the terminal sterilization using ethylenoxide gas will
be applied with aeration time to minimize residual gas.
4. In step 4, the development stage, in establishing a process to manufacture
the product (designed in step 2) the critical issue is to select an
appropriate manufacturing process with appropriate equipment. Developing
the manufacturing flow includes what kind of equipment
will be used for each step. The process developed in this step may
also include in-process monitoring items, such as a process to verify
the in-process product in the subsequent inspection (test) and a
method to monitor the sterilizing condition.
Copyright © 2003 Marcel Dekker, Inc.
5. In step 5, the qualification stage, the critical issue is that the protocol
for IQ/OQ of the equipment and the facility include the established
method and acceptance criteria. The IQ/OQ report should include the
maintenance program to keep the equipment in good condition for
reproducibility of the product. For qualification of the equipment and
process for terminal sterilization, the following standards should be
referred to: ISO 13408-1 [6] and 11138-1 [7] for general issues, ISO
11134 [8] and 11138-3 [9] for moist heat sterilization, ISO 11135
[10] and 11138-2 [11] for ethylene oxide sterilization, and ISO 11137
[12] for radiation sterilization.
6. In step 6, the development stage, the critical issue is that appropriate
operating conditions with in-process monitoring parameters must be
developed for efficiency trials. In this step, master record and in-process
monitoring parameters must be developed; that is, the proposed
master record and SOPs relating to manufacture should be prepared
in the report. For the sterilization process, developing in-process parameters
should be carried out based on the following two aspects:
(1) physical performance and (2) microbiological performance with
ISO 11737-1 [13] and 11737-2 [14]. Further, the worst case in the
process shall be established to move to process validation (products
qualification) in ISO 13408-1.
7. In step 7, the validation stage, the critical issue is that the protocol
for performance qualification (utility and environmental conditions
that relate to all products) and process validation (relating only to the
individual product) should include the master record (including inprocess
control monitoring parameters) and acceptance criteria (including
product specification and operation acceptance range). (In
ISO 11385, the process validation described in CFR21. 820 shall be
divided in two categories, such as performance qualification and product
qualification. Performance qualification is same as process validation in
CFR, and product qualification is defined to qualify the process in the
worst case.) The master record and acceptance criteria should be based
on the report of the efficiency trial and approved by QA.
In general, medical devices may be categorized primarily into three types, in
terms of quality control, as described in Table 9.
In type 1, process verification is required because of subsequent functional
specifications for all products. Surgical equipment, such as scissors and tweezers,
contact lenses, and eyeglasses are categorized type 1a. Diagnostic equipment,
such as CT scanners, and treatment equipment, such as infusion pumps
for the introduction of solution types of medicine and surgical aid solutions are
categorized as type 1b. In b, instructions for assembly at the user’s site should be
Copyright © 2003 Marcel Dekker, Inc.
Table 9 Categories of Medical Devices Based on Quality Control Testing
1. Type 1: The product does not comprise a batch, and functional specification tests
are performed for each product. In type 1a, the specification test of the finished
product should be performed prior to the release from manufacturer. In type 1b,
because the product is finished with in-process products by assembling at the user
site, the specification test of each in-process product should be performed prior to the
release from manufacturer and the specification test of the finished product should be
performed at user site.
2. Type 2: The product comprises a batch and functional specification tests are performed
with representatives of each batch prior to the release from manufacturer.
3. Type 3: In-process product does not comprise a batch, as in type 1, and functional
tests are performed for each in-process product. However, when put together in the
specific process such as sterilization process, the specification test is performed with
representative of the finished products.
“Comprising a batch” means that products are manufactured in one controlled condition
from starting materials to finished product such as ophthalmic irrigating solution in vial
form. A product that does not comprise a batch is manufactured individually, such as
eyeglasses.
in the document. Some products of type 1a are designed for individual patients,
according to the specifications in diagnosis, and design verification and development
of direct in-process product parameters are thus critical factors. With products
of type 1b, development of operating procedures to perform consistently,
is also included as critical-factor because of the necessity of adequate diagnosis
and treatment.
In case of type 2, process validation is required because of subsequent specifications
not being tested; that is, the specification test is done with representatives
in the batch. In this type, viscosurgical solutions not including pharmacological
agents, central venous catheters and other surgical tubing, and surgical thread are
categorized. The process of development and validation for manufacturing this
type are the same as for medicine composed in batches, such as intravenous injection
solution. Product that is not specifically for an individual patient is designed
to apply to all patients. In general, manufacturing processes for many products in
this category are performed continuously. Monitoring only the operating conditions
of the machinery and equipment that manufacture the product and the end
point of each process is established with operating conditions such as operating
time, temperature, pressure, and stirring speed; that is, the end point of each process
does not include the specifications of the in-process product. Finally, only
the specifications of the finished product are tested.
In the case of type 3, process verification is required to produce the inprocess
product as type 1, but process validation is required to manufacture the
Copyright © 2003 Marcel Dekker, Inc.
finished product as type 2. In this type, intraocular lenses and surgical equipment
needing sterilization are categorized; that is, sterilization is performed by
composing batch and development and validation of indirect, in-process parameters
and this process is critical.
In the above situation it must be assured that each process can produce
in-process product with the intended specifications, even without an in-process
product specification test, by monitoring operating conditions of the machinery
and terminating the process with the intended end point of operating the machine.
Briefly, the establishment of an end point of each process only with
operating conditions must assure that in-process product in each process meet
the intended specification. It may thus be important that the end point of each
process must be established by testing the in-process product specified properties
in the development step; that is, the end point of each process must be
determined based on the specified properties scientifically, which must be a
critical factor for the specified properties of finished product. Validation is required
to assure that the operating conditions including the end point of each
process, can produce appropriate in-process product, satisfying critical specified
properties in each step without in-process product specification tests; that is, it
may be that validation is required in order to omit the in-process product specification
test.
One example for type 3 in Table 9 is the intraocular lens (IOLs), and the
validation may be performed as follows according to Figure 2.
Because IOL is implanted, ISO 11979-2 [15] and 11979-3 [16] for IOL
describe the standards of the specifications for physicochemical, microbiological,
and tissue compatibility, along with the requirements for preclinical safety
study and clinical study and packaging. Based on the specifications in ISO
11979-2 and 11791-3, the design of IOL, including such elements as shape and
diopter, is restricted by registration and administrative approval. The following
steps are thus considered for validation for IOL manufacture:
1. Document of material specifications and test methods. Verification of
the specifications must be done to satisfy the design, and the test
method must be validated where needed. Because the material is a
critical safety factor, the selection of material for IOL should meet
both the physicochemical and compatibility specifications described
in ISO 11979-2 and 11797-3. The in-house (receiving) specifications
of material should thus be documented. Where a test method is developed,
the method must be validated. The equipment used for the test
must be calibrated.
2. Document of specifications of IOL with shape and diopter. Verification
of specifications must be done to assure the design has been
followed. Because shape and diopter are critical functional factors for
IOL and should be registered by administrative approval, the design
Copyright © 2003 Marcel Dekker, Inc.
should be established in the document. Where the test method is developed,
the method must be validated. The equipment used for testing
must be calibrated.
3. Master record for manufacture. The master record must include the
method to test the functional factor, and the process that includes inprocess
product testing must be validated. Master records should include
all operations in manufacturing IOL in detail. Critical steps for
manufacturing IOL should be a cutting/polishing step or molding step
for shape, a grinding and polishing step for diopter, and a sterilization
step.
a. The process that relates to the shape and diopter of IOL must be
controlled individually by in-process tests, including measurement;
that is, because the product is not composed in batches, a
manufacturing record exists for the individual product. This process
must thus be verified for each product by the method of a
double-check. Where the manufacturer develops the test method,
the method must be validated. The equipment used for testing
must be calibrated.
b. The process for sterilization, is a critical step for safety, and
should be performed for IOL in the batch unit. Because the sterilization
process cannot be fully verified by subsequent inspection
and testing for each product, this process must be validated using
both chemical and biological indicators to establish the operating
conditions recorded in operating monitoring parameters.
VII. RISK ASSESSMENT FOR VALIDATION
Because validation is required to establish the quality of the medical device,
including reproducibility, each process shall undergo risk assessment. Risk assessment
includes two criteria: (1) how the process can avoid the appearance of
rejected goods or other unsatisfactory goods in each process, and (2) how the
in-process parameters, including in-process product specification, can detect
goods to be rejected or otherwise unsatisfactory goods. Risk assessment for
medical devices is thus required to provide satisfactory goods to customers by
controlling the manufacturing process and by testing in-process product as well
as final product.
REFERENCES
1. ISO 13485. Quality Systems–Medical Devices: Particular Requirement for the Application
of ISO 9001. Switzerland (1997).
2. U.S. Food and Drug Administration. Guidance on General Principles of Process
Validation. (1987).
Copyright © 2003 Marcel Dekker, Inc.
3. ISO 9001. Quality System–Model for Quality Assurance in Design, Development,
Production, Installation and Servicing. Switzerland (1994).
4. Code of Federal Regulations (CFR), Title 21. Part 820.5: Quality Assurance Program;
Part 820.20(a): Quality Assurance Program Requirements. Washington, DC:
U.S. Government Printing Office (1996).
5. Global Harmonization Task Force. Guidance on Quality Systems for the Design
and Manufacture of Medical Devices. (1994).
6. ISO 13408-1. Aseptic Processing of Health Care Products—Part 1: General Requirements.
Switzerland (1996).
7. ISO 11134. Sterilization of Health Care Products—Requirements for Validation
and Routine Control—Industrial Moist Heat Sterilization. Switzerland (1998).
8. ISO 11138-1. Sterilization of Health Care Products—Biological Indicators. Switzerland
(1998).
9. ISO 11138-3. Sterilization of Health Care Products—Biological Indicators Part 2:
Biological Indicators for Moist Heat Sterilization. Switzerland (1998).
10. ISO 11135. Sterilization of Health Care Products—Requirements for Validation
and Routine Control of Ethylene Oxide Sterilization. Switzerland (1998).
11. ISO 11138-2. Sterilization of Health Care Products—Biological Indicators Part 2:
Biological Indicators for Ethylene Oxides Sterilization. Switzerland (1998).
12. ISO 11137. Sterilization of Health Care Products—Requirements for Validation
and Routine Control—Radiation Sterilization. Switzerland (1998).
13. ISO 11737-1. Sterilization of Medical Devices, Microbiological Methods—Part 1:
Estimation of Population of Microorganisms on Products. Switzerland (1998).
14. ISO 11737-2. Sterilization of Medical Devices. Microbiological Indicators—Part 2:
Tests of Sterility Performed in the Validation of a Sterilization Process. Switzerland
(1998).
15. Iso 11979-2. Ophthalmic Implants—Intraocular Lens—Part 2: Optical Properties
and Their Test Methods. Switzerland (1999).
16. ISO 11979-3. Ophthalmic Implants—Intraocular Lens—Part 3: Mechanical Properties
and Their Test Methods. Switzerland (1999).
Copyright © 2003 Marcel Dekker, Inc.
7
Validation of Biotechnology
Processes
Gail Sofer
BioReliance, Rockville, Maryland, U.S.A.
I. INTRODUCTION
Validation of biotechnology processes is generally more complex than validation
of more traditional synthetic or naturally occurring small molecule drugs.
The level of complexity depends on the type of biotechnology product. Biotechnology
products range from synthetic oligonucleotides and peptides to plasmids,
recombinant-DNA-derived and transgenic proteins, monoclonal antibodies, gene
therapy vectors, and some cell-based therapies. The more complex the product,
the more difficult validation becomes. The degree of difficulty is usually linked
to an inability to fully characterize the product and the manufacturing process.
For example, one of the most complex products is human cells treated with a
gene therapy vector or protein and delivered to the patient. Other factors that
contribute to the complexity are the known or unknown risks associated with
some of the sources of biotechnology products. In spite of the diverse range of
biotechnology products, however, there are some commonalities in validation
of the manufacturing processes. There are, in fact, many validation issues that
are identical to those associated with traditional pharmaceutical products, including
facility and equipment qualification, validation of water and aseptic processing
systems, and computer validation. These topics are addressed elsewhere
in this book.
Before a biotechnology process can be validated, it is essential to evaluate
the inherent risk factors associated with the product source, raw materials, and
processing operations. Furthermore, the analytical methods that allow characterization
and validation of the process, as well as characterization of raw materi-
Copyright © 2003 Marcel Dekker, Inc.
als, process intermediates, and final product, must be validated. For plasmids,
recombinant-DNA-derived proteins, monoclonal antibodies, and gene therapy
vectors, manufacturing unit operations generally start with fermentation or cell
culture, which is followed by product recovery and subsequent purification by
multiple steps to produce the purified bulk. A flow scheme for a typical biotechnology
process is shown in Figure 1, and Figure 2 illustrates the process flow
for production of a monoclonal antibody. This chapter discusses the risk factors
that must be addressed during validation, the analytical tools necessary for validation,
the validation of the unit operations employed in typical biotechnology
processes, the timing of validation-related activities, and current and future issues
in validation of biotechnology processes.
II. RISK FACTORS
Validation starts with good process design, which permits reduction of the risk
factors to an acceptable level. Once the process is well characterized it can be
validated. It is essential to know where in the process the risk factors are removed
and how much risk will be incurred if a manufacturing deviation occurs.
Process validation provides such information.
A. Product Sources and Raw Materials
Most of today’s approved biotechnology products are produced in bacteria,
yeast, or mammalian cells. Newer sources currently used to manufacture clinical
trial materials include insect cells, transgenic animals, and gene therapy vectors.
Other potential sources include transgenic plants and nonviral delivery systems
Figure 1 Flow scheme for production of a recombinant DNA-derived protein produced
in mammalian cells.
Copyright © 2003 Marcel Dekker, Inc.
Figure 2 Process flow diagram for production of a monoclonal antibody. (From Ref. 47.)
Copyright © 2003 Marcel Dekker, Inc.
for gene therapy. Each of these poses unique risks—both known and potentially
unknown. Table 1 summarizes some of the known risks associated with several
commonly used sources. In addition to the source material, raw materials used
in establishing cell banks, in fermentation or cell culture, and in processing may
add to the complexity of validation. For example, animal sera are often employed
to enable cells to grow in culture and to stabilize them in storage. Commonly
used porcine and bovine products have the potential to transmit viruses
to the cells, and bovine products may be contaminated with transmissible spongiform
encephalopathies (TSEs; e.g., bovine spongiform encephalopathy, BSE).
In some cases, the potential risk factors listed in Table 1 are associated with
raw materials.
Bacteria and yeast pose no known risks that are associated with viruses
and TSEs. Provided raw materials are free from these agents, validation can
proceed without considering viral and TSE clearance. Insect cells grow at lower
temperatures than mammalian cells, yet it has been shown that viruses known
to infect humans can be maintained in an insect culture [1]. As of this writing
there are no licensed therapeutic products produced in insect cells, so the requirements
are not yet well defined. It appears, however, that most firms perform
viral clearance studies prior to submitting a biologics licensing application
(BLA). Mammalian cells, on the other hand, have been shown to harbor viruses
known to infect humans. Transgenic animals, such as goats or cows, may harbor
infectious viruses and even TSEs that have the potential to be copurified with
the product. Gene therapy viral vectors currently in clinical trials include retroviruses
and adenoviruses, which also can infect humans. Allogeneic cellular bio-
Table 1 Potential Sources of Biotech Materials and Their Associated Risks
Gene
therapy Cellular and
Potential Insect Mammalian Transgenic viral gene therapy
risks Bacteria Yeast cells cells animals vectors combination
Virus ? ? + + + + +
TSEsa ? ? +/? +/? + +/? +/?
Endotoxin + ? ? ? ? ? ?
Nucleic acid + + + + + + +
Proteins + + + + + + +
aWith the exception of transgenic animals, the risk is generally associated with animal-derived products
used in cell culture and other processing steps.
Note: +Potential risk, ?no known associated risk, +/?risk from TSEs potentially associated with animalderived
product used in processing.
Copyright © 2003 Marcel Dekker, Inc.
technology products probably present the greatest viral risk since the donor cells
as well as the manipulation (e.g., with viral vectors) performed on them may
lead to introduction of infectious virus into the patient.
Endotoxins are found in some bacterial sources, such as E. coli. For other
products they are considered a contaminant that should not be present and can
be controlled by adherence to good manufacturing practices (GMPs). Nucleic
acids, once considered a significant risk, are now thought of as cellular impurities,
and their removal should be validated [2,3]. Proteins that pose a potential
risk (e.g., immunogenicity) include host cell proteins, aberrant protein product,
proteins used in cell culture, and those associated with the process (e.g., protein
A affinity ligands or nucleases employed to reduce viscosity).
B. Processing Risks
Variability in cell culture may lead to unexpected expression of an adventitious
agent. Proteolytic degradation and aggregation may result in aberrant product
forms that change potency or are immunogenic. During recovery and purification
operations, variability in processing materials may lead to changes in product
quality. Leachables from chromatographic resins, filters, and equipment
components may be toxic and/or immunogenic. Buildup of contaminants may
occur, with the potential for an unexpected release into the product stream. All
of these risks can be countered by putting into place raw materials’ screening
and acceptance criteria, by designing robust processes that can clear known and
potential unknown risks, by establishing realistic specifications for controlling
each unit operation, by employing suitable validated analytical methods for analyzing
processes, and by adhering to CGMPs to avoid contamination.
III. ANALYSIS AND THE CONCEPT
OF WELL-CHARACTERIZED
BIOTECHNOLOGY PRODUCTS
Before the process can be validated, it is essential to validate the analytical
methods that provide the data that enable processes to be understood and controlled.
Although the same is true for small molecules and other drugs, the
task of analyzing most biotechnology processes and products is generally more
complex [4]. The most frequently employed analytical methods are listed in
Table 2. Peptide mapping has been widely used to demonstrate a difference of
only one amino acid between a protein product and an aberrant form. The use
of mass spectrometry has increased greatly over the last few years and provides
information on molecular weight of intact product as well as identification of
impurities by mass. In combination with other techniques, such as peptide map-
Copyright © 2003 Marcel Dekker, Inc.
Table 2 Frequently Employed Analytical Methods for Process Validation
Methods Detection
Peptide mapping Impurities
Mass spectrometry Purity and impurities, molecular weight, glycosylation
HPLC Purity, impurities, carbohydrate analysis
Electrophoresis Purity, impurities, glycoforms
Bioassays Potency, tertiary structure
Western blot Protein impurities
Carbohydrate analysis Glycoforms, carbohydrate sequence
PCR DNA, viruses, mycoplasma
Nucleic acid sequencing Genetic stability
PCR, polymerase chain reaction.
ping, mass spectrometry can confirm primary structure and posttranslational
modifications, such as glycosylation. The use of tandem-mass spectrometry for
rapid identification of proteins was reviewed by Dongre et al [5]. Ion exchange
and reverse-phase high performance liquid chromatography (HPLC) are employed
for both in-process and product assays and for carbohydrate analysis.
Size-exclusion HPLC enables assessment of aggregates. Stability-indicating
assays are also essential for intermediates and final product. Further information
on stability testing is provided by the International Conference on Harmonization
(ICH), and some of the analytical methods currently employed are discussed
by Reubsaet et al. [6,7]. A 1995 review discusses the major pathways of
protein degradation [8].
Bioassays may be the most important assays since they are often the only
available tools for determining the correct tertiary structure of complex protein
products and the activity of even more complex biotechnology products. Bioassays
are also the most problematic assays, and the variability may be 50% for
animal-based bioassays. New developments in sensor technologies may improve
both the speed and accuracy of bioassays [9]. The development of hematopoietic
stem cells for in vitro assays has the potential to increase both the accuracy and
the speed of bioassays [10].
Another complex assay is the host cell protein assay, which can take more
than a year to develop and usually requires that culture conditions be established
at least at a pilot scale [11,12]. Host cell proteins may vary with the culture
conditions, including scale of operation. As a result, the panel of antibodies
generated against host cell proteins will need to be generated against host cell
proteins expressed under controlled conditions used for manufacturing of pilot
or full-scale supplies. Conditions are usually not established until phase III clinical
trials, however, and this leads to significant timing problems in many cases.
Copyright © 2003 Marcel Dekker, Inc.
The inability to pick up all host cell proteins is another problem faced in development
and implementation of these assays.
For firms that manufacture several products from one source (e.g., Chinese
hamster ovary [CHO] cells), a generic approach may suffice. Regulatory
authorities in some countries are accepting this approach [13]. There are also
some generic kits on the market that can be used to study host cell protein
clearance during development, and may be considered acceptable for licensure.
Other assays that are required include those employed for cleaning validation,
sterility, bioburden, and mycoplasma. Cleaning validation for biotechnology
processes is described in a PDA publication [14].
It has been stated that “characterization is often technology challenged”
[15]. Using a combination of orthogonal analytical methods does, however, enable
the characterization of biotechnology processes and products. In the past,
the processes used to produce them defined biological products. While this may
still be true for complex vaccines, some blood products, viral vectors, and cell
therapies, many biotechnology products are considered well characterized. It is
difficult to define exactly what well characterized means for all biotechnology
products. To allow for rapid implementation of newer analytical methods as
they are developed, the U.S. FDA dropped the term well characterized as an
official classification of biotechnology products. Instead, the term specified was
applied to therapeutic plasmids, therapeutic synthetic peptides of 40 or fewer
amino acids, therapeutic monoclonal antibodies, and therapeutic proteins produced
by recombinant DNA technology [16]. Most of the information that follows
applies to these products, particularly the latter two.
IV. UNIT OPERATIONS
Fermentation and cell culture provide the necessary quantities of starting material.
Following the growth of the cells to the requisite quantities, the product is
recovered and then purified. For each unit operation there are some specific
validation issues that may be discussed. Some common features apply to all of
these manufacturing steps, however. The processing times for each unit operation
must be defined and the process validated within established time limits.
Biological products are usually much more labile than traditional drug products
and validation of stability is essential. Often the conditions that maintain product
and intermediate stability are ideal for the growth of micro-organisms. Even if
the micro-organisms are removed, they may potentially leave behind toxins and
other harmful substances that can cause product degradation or copurify with a
protein or nucleic acid product. Temperature, pH, conductivity, product concentration,
presence of impurities (e.g., proteases in the initial feedstream), process-
Copyright © 2003 Marcel Dekker, Inc.
ing times, and product concentration may all affect stability, which must be
validated for in-process intermediates, final bulk, and final product.
Bioburden and endotoxin specifications should be established and adhered
to for each step. Holding times between steps and prior to cleaning must be kept
within predetermined specifications. Cleaning validation is another concern that
many biotechnology firms must address for each unit operation. This can be
particularly problematic for the manufacture of material made in small quantities
in facilities in which more than one product is produced. Although the biotechnology
industry now has access to equipment that is of a sanitary design for
pilot and full-scale manufacturing, this is not always the case at smaller batch
sizes, such as those often used to produce clinical supplies or even for some
high-potency, small-dosage products. For example, chromatography systems for
small-scale batches often have threaded fittings, which make both cleaning and
sanitization difficult.
During development, control parameters are optimized for each unit operation.
During the preparation of the validation batches (i.e., three to five consistency
batches at pilot or full scale, generally during phase III pivotal clinical
trials), the control parameters are tested by determining the outputs under worstcase
conditions. With biotechnology processes, the variables clearly impact one
another. For example, a change in pH may impact the required conductivity
range that enables production of the desired product. Multifactorial analysis is
often used to minimize the number of runs that must be performed during validation
of modern biotechnology processes [17]. There are many approaches to
process validation and there are some who advocate testing all parameters to
the edge of failure. This approach can be very costly. Others in the biotechnology
industry advocate only testing to the edge of failure those parameters likely
to cause variability. For example, temperature can be rigorously controlled
within a very narrow range. In designing validation studies, it is cost-effective
to maintain this control and avoid pushing the process to fail at temperatures
outside the specified range.
A. Cell Culture
Cell culture is the first production step for a typical biotechnology product made
in eucaryotes (organisms that contain a nucleus and membrane-bound organelles).
Chinese hamster ovary cell lines are one of the more commonly used
sources for production of recombinant DNA-derived proteins, and will be used
here to illustrate some of the common validation issues. The culturing process
cannot be validated without first defining raw materials and characterizing the
cells [18,19]. A master cell bank (MCB) and a working cell bank (WCB) are
prepared and characterized. In addition to testing the cell banks, cells are tested
at the end of production and the unprocessed bulk is also tested. The history of
Copyright © 2003 Marcel Dekker, Inc.
the cell line, including potential previous exposure to animal and human substances,
is documented. Depending upon what is known about the source and
the history of the cells, a testing program is designed and implemented. It should
follow the latest regulatory guidances [20]. In the case of CHO cells, cell line
characterization includes determining if the cells are truly what they are thought
to be. Isoenzyme analysis is commonly used. Banding cytogenetics provides the
most sensitive identity test, with the capability to detect an impurity of 1%
[21]. Testing also requires the use of validated assays for detecting mycoplasma,
bacteria, fungi, and viral contamination. Cells are tested for the presence of both
endogenous and adventitious virus. Cells such as CHO cells are known to have
retroviral particles. Electron microscopy has historically been used to determine
the retroviral particle load, and has the added advantage of being able to detect
other viruses. Today, polymerase chain reaction (PCR) is also being used. During
process validation the ability of the process to remove retroviral particles to
a level beyond the maximum that could be found in the unprocessed bulk material
is validated.
The optimal conditions are determined during development of the culture.
Control parameters that provide cell viability, sufficient quantity of viable product,
and an unprocessed bulk that can be purified to the requisite level are evaluated
in development. The kinetics of cell growth, product formation rate, and
total product yield are evaluated. The ability to maintain sterility during sampling
of the bioreactor is validated. Realistic ranges are set for all of the control
parameters, which include in addition to time, dissolved oxygen, temperature,
pH, and motor speed. Measurable outputs include cell density and viability,
product content and quality, and the absence of bioburden. (See Table 3.) Prior
to validation, the bioreactor scale is generally increased. In some cases, 1-L
bioreactors used in development are scaled up to tens of thousands of liters to
meet production needs. As with any scale change, this may alter the acceptable
ranges of the critical control parameters. Of all the unit operations for a biotechnology
process, cell culture is usually the most variable. Cells may be suscepti-
Table 3 Some Operating Variables and
Acceptance Criteria for Cell Culture Operations
Operating variables: Acceptance criteria:
pH Product content
Dissolved oxygen Product quality
Temperature Cell viability
Motor speed Cell density
Bioburden
Copyright © 2003 Marcel Dekker, Inc.
ble to slight variability in the operating parameters, and when the scale is changed,
the control over pH, temperature, and dissolved oxygen must be maintained.
Another factor is the ability to stir the bioreactor at a larger scale without shearing
the cells if the mechanism of stirring changes with the scale change. Furthermore,
the cells may die at different times, resulting in variable protein impurities
and product quality changes that make validation of downstream processing
even more challenging. Changes in scale as well as cell culture media quality
can result in major changes in protein products. If changes in posttranslational
modifications such as glycosylation occur, product potency and immunogenicity
may be altered. Relevant assays must be used in validation to detect changes,
and if changes are observed it may be necessary to re-evaluate product potency,
efficacy, and safety.
In spite of the potential for changes described above, varying scale and
operating conditions for a monoclonal antibody had little impact in one study
that evaluated the effects of extending population doublings, low glucose, and
harvest times outside normal manufacturing ranges. The glycosylation pattern
only changed during the early stages of the bioreactor culture [22]. Clinical
manufacturing had taken place in 20-, 40-, 100-, and 200-L bioreactors. Comparability
of purified product from the different scale cell culture operations was
demonstrated by an ELISA, high-performance size-exclusion chromatography,
oligosaccharide profile evaluation, MALDI-TOF mass spectrometry, electrophoresis,
pharmacokinetics, stability, and process residual profiles. Consistency lots
were made in 500-L bioreactors, and the same tests confirmed that the product
was again comparable. A further change was made when the manufacturing was
transferred to another facility in which the bioreactor scale was from 400 to
10,000 L. Again, no significant differences were observed when the assays described
previously were used.
For some cells, proteases are particularly problematic, causing product degradation
and considerable variability. For production sources such as CHO cells
that secrete glycosylated products, some firms use batch or fed-batch cultures.
Others use continuous cultures, which may be more productive but are generally
more difficult to control and validate. Prior to validation it is necessary to define
the size of each collected pool. It is unlikely that the secreted product can remain
viable for a long time because of proteolytic degradation, aggregation, and other
factors that may cause denaturation. Some firms have genetically engineered cell
lines to reduce protease expression. Bulk harvest pooling criteria and storage conditions
must be established and validated. If five pools are collected, for example,
each must have set acceptance criteria prior to combining them for further processing,
otherwise there is the risk that a firm might combine acceptable and nonacceptable
pools (basically, combining a good lot and a bad one to make a good
one). During validation runs, pools should be analyzed separately.
Prior to further processing of the bulk harvest, it should be tested for
sterility, mycoplasma, and viral contamination. In the case of CHO cells, an in
Copyright © 2003 Marcel Dekker, Inc.
vitro virus detection assay is employed. This testing is performed on every lot.
Electron microscopy is also used to determine the amount of retroviral particles,
but this is typically done on only three to five lots to quantify the viral load as
a starting point for validation of viral clearance [23]. These lots need to be
produced at the scale and with all conditions intended for licensure of a product.
Adamson has described some case studies for CHO cell culture validation and
process characterization [24].
B. Isolation and Recovery
If the product is secreted, recovery may involve a simple filtration step to remove
any cells and cellular debris. Other clarification techniques include centrifugation
and expanded bed adsorption [25]. For such intracellular products as
recombinant proteins produced in E. coli, the product may be denatured and
located in inclusion bodies within the cells [26]. Bacterial cells are typically
concentrated by centrifugation or crossflow filtration, washed, and then disrupted
by homogenization. Inclusion bodies are then isolated, and the protein
product extracted and refolded. Validation of recovery operations for an E. coli
product is described by Seely et al. [27].
Clarification steps must be validated to yield product with a given specification
(e.g., no viable cells and a defined particulate level, if any). The specifications
should enable production of feedstream for the purification steps. Varying
amounts of cell fragmentation during processing can lead to out-of-specification
material in the next step. A recent FDA form 483 noted that for a 3.0-µm filter
used to clarify the fermenter harvest, no study had been conducted to evaluate
the effect of operating the filter at the specified maximum pressure limit on cell
fragmentation.
For products located in inclusion bodies, product extraction and removal
of extraction solutions must be validated. The extent to which the product can be
refolded must be defined. Validation efforts are directed toward demonstrating
consistency of refolding as well as removal downstream of any improperly folded
product.
After the bulk harvest is isolated, stability must be validated for the hold
period prior to further processing. Specifications on the bulk harvest usually
include pH, conductivity, bioburden, endotoxin, and protein concentration, along
with product concentration.
C. Downstream Purification
Chromatography and filtration are the primary downstream purification steps.
In general, three to five purification steps are performed to achieve the requisite
purity for a protein product. The required degree of purity depends on product
indication, dose, patient population, and the risks associated with the impurities
Copyright © 2003 Marcel Dekker, Inc.
derived from the source material. The validation of chromatographic processes
has recently come under more regulatory scrutiny, as evidenced by a review of
recent 483s [28]. The parameters established in development and validated once
the process is characterized include resin and filter characteristics that are relevant
for the specified separation, column packing quality and consistency, product
purity and impurity profiles, and consistency of sanitization and cleaning.
1. Chromatography Resins
Chromatographic resins contain a great deal of surface area, and a clear understanding
of what is occurring on the surface in terms of carryover of risk factors
is not always possible. Cleaning and sanitization, as well as column lifetime,
are issues that must be addressed in development and validated at pilot or full
scale.
Column resins are considered as raw materials and at a minimum must be
quarantined and tested for identity prior to release. Purification processes need
to be validated in such a way that the next lot of resin will not have sufficient
variability to cause a batch failure. This is accomplished by understanding separation
mechanisms, what each step accomplishes (e.g., how much of specified
impurities is removed), and the control parameters under which the acceptance
criteria are met. Control parameters may include product concentration, total
protein concentration, feedstream volume, impurities (both profile and amount),
flow rates, ionic strength, and pH. It is always advisable to use more than one
lot of chromatography resin in development and to evaluate the range of specifications
the vendor provides. For example, it might be useful to test a process at
the limits of the available range of milliequivalents of charge groups for a given
ion exchanger. Although this is part of process design, a process is not capable
of being validated if the variables are not understood and established broadly
during the development stage and tightened as more is learned later in the process.
2. Filters
Filters are used for clarification, removal of small molecules, exchange of buffers,
and concentration of product, as well as sterilization and virus removal. A
recent review of validation of filtration describes the critical validation issues
[29]. Filter compatibility is tested with process conditions to avoid nonspecific
binding of product to the filter or addition of extractables to the process stream.
Extractables are defined and limits established based on final product safety
studies. Special considerations apply for sterilizing filters and those that are
designed for virus removal. These filters are single use, however, which simplifies
the validation effort.
Copyright © 2003 Marcel Dekker, Inc.
3. Column Packing and Storage
The amount of resin to pack in a column, column geometry, flow rates, pressure,
column hardware, and wetted materials of construction should all be evaluated
in development. Chromatography columns must be properly packed prior to
validating the purification process. From a business perspective there should be
some criteria other than purification of the product by which the quality of the
packed column can be assessed prior to applying the feedstream, which by this
time in the process is quite expensive. Height equivalent to a theoretical plate
(HETP) and asymmetry determinations can be used to evaluate the quality of
column packing, but may have limited value for some types of packed columns
[30]. For example, for on–off types of chromatography, such as affinity, the
packing quality may not be at all relevant. For gel filtration, however, asymmetry
determinations may be essential to ensure the column packing will be sufficient
to enable the necessary degree of purification to be achieved. Even when
HETP and/or asymmetry are not relevant to the separation capabilities, measuring
these parameters can sometimes give an indication of other problems associated
with the packed column (e.g., clogging or gross contamination). Most firms
include HETP measurements on a periodic basis to ensure column integrity. The
acceptable ranges of HETP and/or asymmetry values can be determined from
development data that show consistent product purity and impurity profiles with
columns packed to a specified HETP or asymmetry value. Although it may not
be necessary to set a specification for HETP and/or asymmetry, specifications
must be established for both bioburden and endotoxin.
Removal of carbon-containing storage solutions from packed columns is
most often tested by using total organic carbon (TOC) assays to evaluate the
column effluent. Gas chromatography may also be employed during validation
to ensure removal of ethanol, which is commonly used in shipping of chromatography
resins. During storage, an additional cleaning effect due to extended
contact time with the storage agent may be observed. Resin leakage is also a
possibility. Total organic carbon is sometimes useful to assess the amount of
leakage and validate removal of leakage products prior to reuse of the column
[31]. Questions from regulatory agencies related to storage have included “What
is the expected storage time based on validation studies for the regenerated
column?” and “Provide resin stability data for the proposed base storage conditions”
[32]. In a 1998 approval letter, a firm was told to “institute for every
column run bioburden monitoring of the ion exchange column storage solution
to ensure that storage conditions and storage buffer routinely maintain a bacteriostatic
effect.” In 1999, an FDA warning letter noted that there were no data to
demonstrate bacteriostatic effectiveness of the storage solution for a purification
column.
Copyright © 2003 Marcel Dekker, Inc.
4. Process Validation
Validation of each chromatographic and filtration process step requires the use
of orthogonal analytical methods, some of which may not be incorporated into
manufacturing. For each step it is important to define acceptable ranges for all
control parameters and set acceptance criteria on purity and impurities. A clear
understanding of what each step is achieving is essential. Some firms use the
term forward processing criteria to describe the values of various parameters
that must be achieved to allow the process to continue. The forward processing
criteria are defined in development and then modified as the process is further
understood. (See Table 4.)
Minor changes in some operating parameters can have major effects on
removal of specific impurities. The variability that might occur in virus clearance
is discussed below. Changes in scale also require validation. Generally,
chromatography and filtration are fairly simple to scale up, and changing scale
in these purification steps is generally not as complicated as the changes that
can occur when cell culture scales are changed.
Whereas shear is not a problem in chromatography, there is a greater
chance for it to occur during filtration. When the scale is changed in filtration,
shear can lead to degraded product. Most of the shear effects occur due to
system design at sites such as valves, elbows, and ports [29].
5. Resin and Filter Reuse
Packed columns are used repeatedly for most biotechnology processes. Regulatory
agencies have expressed concern that column performance may deteriorate
with continued use. Industry has responded by employing resin lifetime studies
at both small and production scales [33]. Validation of the ability to produce
consistent product for the lifetime of the resin is essential, but there are currently
some in industry who believe that small-scale studies extended to the end of
Table 4 Some Operating Variables and
Forward-Processing Criteria for Purification Operations
Operating variables: Forward processing criteria:
Total protein load Product purity
Sample volume Product yield
Conductivity Removal of specific impurities
pH Conductivity
Flow rates pH
Pressure
Copyright © 2003 Marcel Dekker, Inc.
resin use may not be necessary in all cases and that concurrent validation may
be sufficient. The small-scale models are validated by demonstrating that the
chromatographic performance (measured by parameters such as purity, yield,
and removal of specific impurities) is the same as that found at pilot or full
scale. In cases in which in-process monitoring tools are available it may be
feasible to consider concurrent validation.
Unlike sterilizing and virus removal filters, tangential flow filtration (TFF)
filters are often reused. Flow and integrity tests are necessary to ensure the filter
remains the same after usage and cleaning. Consistency of filtrate and retentate
streams is validated using relevant validated assays that are specific for each
process and product.
6. Cleaning and Sanitization of Columns and Filters
Cleaning validation of any component with a large surface area can be problematic.
With chromatography and TFF, the concerns are related to carryover of
product, degraded product, and impurities. These are not sterile processes, and
there is a potential for microbial organisms to be retained on column resins and
filters. Cleaning and sanitization issues have resulted in several FDA form 483s.
One of the reasons a firm was recently told to stop manufacturing a product
was that it had not validated the sanitization of a chromatography resin. A better
understanding of the effectiveness of cleaning protocols and, as a result, the
ability to validate cleaning, should result from the development of more sophisticated
analytical tools. For example, PCR may be of considerable value in
understanding removal of viruses from resins. It is often the lack of detection
tools that causes concerns related to carryover.
Most of today’s resins and filters can be cleaned and sanitized with agents
such as sodium hydroxide, which has been shown to be very effective [34]. In
some cases, however, affinity chromatography ligands, especially those that are
proteinaceous, are not resistant to the rather harsh conditions necessary to inactivate
viruses, fungi, and bacteria or to remove residual product and impurities
7. Leakage and Extractables
Leakage from chromatography resins, filters, and wetted equipment components
should be investigated. Most leakage occurs during the use of harsh solutions
employed for cleaning and sanitization, but leakage may also occur during storage
of chromatography resins. Validation of removal of leakage products from
the product may be necessary. This is particularly true when affinity chromatography
is employed. The leakage product is usually a complex of ligand and
product, which may be immunogenic. Although the amount may be very small,
it should be validated that subsequent steps will remove any potential leachables
Copyright © 2003 Marcel Dekker, Inc.
to an acceptable level, which is determined by performing a risk assessment
based on the product dose and indication as well as patient population.
Filter extractables are usually identified and tested for biological reactivity.
Weitzmann has described the use of model solvents for evaluating filter
extractables [35]. Unlike filters, most commonly used chromatography resins
are carbohydrate-based, and while data on the toxicity and biological activity of
leachables should be available, it is generally not as great a concern. On the
other hand, the same principles used for testing filter extractables may be applicable
for new polymers used in chromatography.
8. Validation of Viral Clearance
Validation of viral clearance is a major concern for products derived from mammalian
cell culture and transgenic animals, as well as for viral vectors used for
gene therapies. As we learn more and more about potential risks from newly
found viruses, the requirements for validation increase. The increased concerns
may be reflected in the number and types of viruses that are used for viral
clearance studies. Both relevant and model viruses are used. A recent review of
validation of the purification process for viral clearance evaluation provides
further information on selection of viruses and performance of the studies [36].
Several documents describe the requirements for viral clearance studies.
The ICH guidance on viral safety evaluation provides information on the design
of viral clearance studies and their interpretation [37]. Unlike most other aspects
of process validation, viral clearance cannot be performed at full scale. There
are several reasons for this. Direct testing methods may not detect low concentrations
of virus, which requires that viruses be spiked into the feedstream.
Assays may detect only known viruses, and they may also fail to detect variants.
Worker safety is another issue that necessitates the need to perform the validation
at a small scale. Scaling down is addressed in the ICH guidelines and in
the literature [38,39].
Inactivation, filtration, and chromatography are commonly used to clear
viruses. Clearance may be due to inactivation of viruses or to physical removal.
Commonly used inactivation techniques include low pH, solvent/detergent treatment
for enveloped viruses, and severe heat treatment. Removal is commonly
achieved with specially designed filters or by chromatography. Removal by
chromatography is often subject to variability in operating parameters. Inactivation
and filtration are usually considered robust (i.e., not subject to slight changes
in operating conditions). Clearance of viruses by filtration has been discussed
by Aranha-Creado [40]. Regardless of the clearance mechanism, each feedstream
must be challenged with a virus spike and the clearance analyzed at small scale
after ensuring that the small scale is validated to represent manufacturing conditions.
Copyright © 2003 Marcel Dekker, Inc.
Viral detection assays based on infectivity suffer from significant variability,
which necessitates the use of statistical evaluation. Polymerase chain reaction-
based assays are currently being developed and validated for viral clearance.
With PCR assays, there is a potential to distinguish between inactivation
and physical removal, perform mass balance studies, evaluate more than one
virus at a time for a given process step, reduce the time for completing clearance
studies, and accurately quantitate the amount of virus bound to such surfaces as
chromatography resins. Table 5 compares the assay precision between an infectivity
assay and a quantitative PCR assay.
Regardless of which assays are used, there are many variables that must be
controlled during viral clearance evaluation. Some of these are listed in Table 6.
V. WHAT TO DO WHEN
There is clearly much to do to validate a biotechnology process. Obviously not
all of it can be accomplished prior to entering clinical trials. As a process is
designed, documentation should be sufficient so that the rationale for the devel-
Table 5 A Comparison of Precision Between an Infectivity
and a PCR Assay
TCID50 QRT-PCR
(individual results) (individual results)
3.55 ? 107 4.29 ? 109
1.51 ? 107 3.83 ? 109
2.69 ? 107 3.76 ? 109
2.00 ? 108 4.21 ? 109
6.31 ? 107 3.64 ? 109
8.51 ? 107 3.60 ? 109
4.79 ? 107 3.67 ? 109
6.31 ? 107 3.94 ? 109
2.00 ? 107 3.76 ? 109
4.79 ? 107 3.70 ? 109
6.31 ? 107 3.21 ? 109
3.55 ? 107 4.06 ? 109
1.12 ? 107 3.33 ? 109
2.00 ? 107 3.62 ? 109
3.55 ? 107 4.02 ? 109
8.51 ? 107
Average = 5.34 ? 107 Average = 3.78 ? 109
Standard deviation = 4.54 ? 107 Standard deviation = 0.30 ? 109
CV = 85% CV = 7.9%
Copyright © 2003 Marcel Dekker, Inc.
Table 6 Some Variables in Virus Clearance Validation Studies
Virus selection
Virus titer
Buffer/product interference
Buffer/product cytotoxicity
Suitable spiking and sampling points
Scale-down
Effect of spiking on process step
Freeze-thaw effect on enveloped viruses
opment of a given process is clear. Understanding the risks and the process
capabilities enables a graduated approach to be taken.
At the earliest stages of clinical trials it is likely that many changes are
still being made to improve the process and resulting product. The use of suitable
analytical tools to assess process changes is essential at this stage when the
characterization of the product and process is not as complete as it will be by
phase III. It is likely that more assays will be employed early on than at later
stages when there is less variability in the process. Relevant assays are essential
to link pharmacological and toxicology batches to clinical trial batches.
Prior to phase I clinical trials, process steps and assays that relate to safety
should be validated. For example, sterility assays and sterilization processes
must be validated. Cell lines should be qualified prior to any clinical trials,
including testing for adventitious agents and identifying and quantifying indigenous
virus. Virus clearance steps should be validated, and removal of any potentially
toxic or otherwise harmful agents should be validated [41,42].
The product structure should be described in detail and there should be an
estimate of the stability based on biological activity. The assays used to determine
structure and stability will most likely be qualified, but not fully validated
at this stage. Considerable thought must go into qualification of the methods
upon which structure and stability are assessed at this early stage, however. One
of the most important activities at this early stage is putting aside retention
samples that are stored properly and can be used to evaluate the impact of
process changes.
By phase II, stability assays should be validated and a good faith effort
made to validate all in-process tests. Release assays should also be validated.
Removal of product and process-related impurities should be demonstrated. Stability
of cells during growth should be validated.
During phase III any effects of scale changes should be validated and
multiple lots placed on stability test. Extensive viral clearance studies should be
Copyright © 2003 Marcel Dekker, Inc.
performed where relevant. Host cell protein and in-process assays are typically
validated at this stage. Potency assays should be validated prior to submission
of a license application. Process validation at phase III usually results in a better
understanding of the process and frequently enables specifications to be tightened.
VI. CURRENT AND FUTURE ISSUES
Current and past FDA 483s provide insight into concerns expressed by regulatory
authorities. When reading these documents it is important to recognize that
we do not have the full picture. On the other hand, we may gain valuable information.
Validation is a common cause for issuance of 483s. Some recent 483s
are shown in Table 7.
Validation of biotechnology processes should provide assurance of consistent
product quality. Too often firms spend inordinate amounts of time on equipment
qualification and ignore some of the more important elements of process
validation. Some firms do too much; others don’t do enough. Although safe and
efficacious biotechnology products have been on the market for some time, it is
clear from recent gene therapy trials and from available knowledge of cell lines
that there are potential and sometimes significant risks. Over the last decade,
however, the biotechnology industry has learned that certain controls and validation
efforts enhance product safety. This has led some to suggest a generic
approach can be taken for some aspects of process validation for some previously
used cell lines. For example, the use of generic viral clearance studies
Table 7 Some Comments Related to Problems Associated with Validation
In-process and release testing assays not validated.
Stability data to support intermediate product hold period not adequate; did not include
three consecutive lots held for the expiry period.
No investigation regarding variability of peak cutting. Peak cutting is conducted to accommodate
capacity of vessel.
Cleaning validation of resins at end of lifetime use did not demonstrate removal of endotoxins
after sanitization and cleaning.
Cause of sudden change in output volume not determined.
No demonstration of bacteriostatic effectiveness of storage solution used for chromatography
column.
No data available to demonstrate assays used in stability testing of bulk are stability
indicating.
Process validation did not start with predetermined in-process specifications.
Copyright © 2003 Marcel Dekker, Inc.
Table 8 Currrent and Potential Trends in Validation of
Biotechnology Products
Generic validation
Concurrent validation for resin lifetime
Combined clearance studies
Increased use of comparability protocols for validated changes
Potential new risks found by increasingly sensitive assays
is discussed in the U.S. FDA’s Points to Consider in the Manufacture and
Testing of Monoclonal Antibody Products for Human Use [43]. Others have
suggested a generic approach to validation of removal of host cell proteins and
DNA from CHO cell-derived products [44]. This somewhat controversial approach
has some merits, but clearly depends on knowledge of the risk factors,
previous experiences, and the patient indication. In some cases, a generic approach
may expedite the delivery of lifesaving drugs.
A few other issues related to process validation are under discussion. One
is resin lifetime. Some firms are proposing concurrent validation rather than
generating prospective laboratory scale for the entire lifetime. The concurrent
approach would probably require more in-process testing, but the data generated
may be more reliable since they are obtained at manufacturing scale. Clearly,
eliminating the small-scale studies at this time for steps in which viral clearance
is claimed will be quite difficult if not impossible.
The specificity of PCR should make validation efforts for the clearance
of viruses, DNA, and host cell proteins more efficient by combining studies and
increasing the speed of the assays. In the case of DNA, the assay sensitivity
may enable validation to be performed at full scale and eliminate the need for
more costly and less accurate small-scale spiking studies.
Today’s analytical tools enable changes to be made and validated for comparability
so that beneficial changes can be implemented more rapidly. Comparability
protocols have already been approved for several changes, including
extension of cell culture time and scale up of chromatography [45,46]. As more
sophisticated validatable analytical tools enable the demonstration of comparability,
more validated changes will be implemented to improve product quality
and the efficiency of manufacturing (Table 8).
VII. CONCLUSIONS
Validation requires good process development. This is especially relevant in
biotechnology, in which complex biological systems are usually involved. These
biological systems have inherent risks, and validation of removal of both known
Copyright © 2003 Marcel Dekker, Inc.
and potential risk factors is essential for the continued manufacture of safe and
efficacious therapeutics [47].
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Copyright © 2003 Marcel Dekker, Inc.
8
Transdermal Process Validation
Charlie Neal, Jr.
Diosynth-RTP, Research Triangle Park, North Carolina, U.S.A.
I. INTRODUCTION
Tablets, liquids, inhalants—transdermals? What exactly are these “skin
patches?” Why are they so special? Are they considered the “in medicines” of
the last decade? How are they validated?
This chapter will provide an answer to each of these important questions.
It will begin by providing a definition of what transdermals are, citing the advantages
of these innovative drug types, and the difficulties associated with their
manufacture. It will then discuss the basic elements of transdermal validation,
breaking the program into manageable “pieces.” The focus will shift to discussing
the unit operations required in the manufacture of matrix transdermals. The
stage for the main section of this chapter will be set with a discussion of the
individual components that must be qualified in support of process validation.
Covered as parts of that discussion are the equipment and process qualification
steps. The process qualification steps are broken down into real-world activities
that support successful process qualification: process development; process
ranging studies; scale-up studies, demonstrations, and trials; and process-specific
validations. Each of these activities serves to increase confidence and familiarity
with the qualification activities. The chapter will then divert and briefly discuss
potential problems and resolutions associated with transdermal processes.
The focus then shifts to a discussion of transdermal process validation.
This particular discussion will share a method for completing this critical step.
Although the method for completing validation for transdermals is important,
there are two other items that must not be forgotten: validation documentation
and the establishment of a solid change control program. Later sections of this
chapter will discuss each area in adequate detail. As the chapter draws to a
Copyright © 2003 Marcel Dekker, Inc.
close, a brief recommendation of how to prepare for a preapproval inspection is
included.
II. TRANSDERMALS DEFINED
Before discussing transdermals, let us first acknowledge that the current good
manufacturing practices (CGMPs) are regulations established by the U.S. Food
and Drug Administration (USFDA). These regulations not only serve as the
operating “Bible” for drug manufacturers, but also provide operating directions
in the area of manufacture, processing, packing, and holding of drugs. In reality,
the GMP regulations are the conscience of reputable manufacturers as they produce
drug products.
A transdermal is one such drug. What does the term transdermal mean?
Trans means through and dermal means skin, therefore a transdermal drug is
one absorbed through the skin. The United States Pharmacopeia (USP) 24 [1],
offers the following definition/discussion of a transdermal delivery system:
Transdermal drug delivery systems are self-contained, discrete dosage
forms that, when applied to intact skin, are designed to deliver the drug(s)
through the skin to the systemic circulation. Systems typically comprise an
outer covering (barrier), a drug reservoir, which may have a rate controlling
membrane, a contact adhesive applied to some or all parts of the system
and the system/skin interface, and a protective liner that is removed before
applying the system. The activity of these systems is defined in terms of
the release rate of the drug(s) from the system. The total duration of drug
release from the system and the system surface area may also be stated.
Transdermal drug delivery systems work by diffusion: the drug diffuses
from the drug reservoir, directly or through the rate controlling membrane
and/or contact adhesive if present, and then through the skin into
the general circulation. Typically, modified-release systems are designed to
provide drug delivery at a constant rate, such that a true steady state blood
concentration is achieved and maintained until the system is removed. At
that time, blood concentration declines at a rate consistent with a patient’s
pharmacokinetics.
Transdermal drug delivery systems are applied to body areas consistent
with labeling for the product(s). As long as drug concentration at the
system/skin interface remains constant, the amount of drug released from
the dosage form does not change or influence plasma concentrations, due
primarily to steady state absorption in the blood stream. The functional
lifetime of the system is defined by the initial amount of drug in the reservoir
and the release rate from the reservoir.
In general, a typical female-oriented hormonal transdermal system will provide
approximately 20 times higher systemic availability of the hormone after administration
than that obtained after oral administration [2].
Copyright © 2003 Marcel Dekker, Inc.
The facts listed above may explain why the utilization of transdermals has
been on the increase in recent years. It would be good to note that countless
manufacturers are now in the transdermal marketplace, with drugs ranging from
nitroglycerin to hormones. In addition to the aforementioned facts, one of the
main reasons, is that transdermal medications offer several advantages over
other more common dosage forms. Some noteworthy advantages are that transdermals
Provide improved systemic bioavailability of the active ingredients
Permit slow, timed release of the active
Avoid the affect of a bolus drug dose
Provide for multiple daily doses with a single application
Provide a means to quickly terminate dosing
Provide instantaneous identification of medication in emergency
The last item may benefit from a bit of discussion. Let us take as an
example a person on hormonal therapy who is admitted into a hospital with a
sudden, life-threatening illness. Strange reactions sometimes occur if certain
drugs are mixed within the body, thus a common concern during hospital admittance
is which medications the patient is taking. If the patient cannot converse
with the medical staff but is wearing a patch, it will be obvious during physical
examination. If on the other hand this person is on oral hormonal therapy, the
attending physician would not immediately know whether or not the medications
prescribed will induce a negative reaction.
While the transdermal drugs offer the aforementioned advantages, their
development, manufacture, and eventual validation also offer perhaps a bit more
of a challenge than other dosage forms. In conjunction with the greater overall
challenge, some noteworthy disadvantages are that
Their process for manufacture is often complex and costly.
They are not a suitable dosing vehicle for certain drugs.
Their absorption profiles may vary from patient to patient due to variations
in skin absorption.
They can cause skin irritation.
They may be conducive to bacterial growth.
Their adhesion time is typically limited.
The overall system quality is often very much dependent on the quality
of the adhesive selected.
It should be noted that at least two distinctly different types of transdermal
patches or systems exist. One of these is the (liquid) reservoir system. The other
is the matrix system. These systems differ both in their manufacturing steps and
in their final product presentation. Key manufacturing steps for both systems
are illustrated in Figure 1.
Copyright © 2003 Marcel Dekker, Inc.
Figure 1 Manufacturing routes for matrix and reservoir transdermal systems.
Copyright © 2003 Marcel Dekker, Inc.
In both systems, the active is first dispersed uniformly in a solution or
gel. In the reservoir system, the homogeneous gel is dispensed onto a card that
is then die-cut to yield individual systems. These systems are then pouched. In
the matrix system, the mixed solution is uniformly coated onto the surface of a
film. The resulting laminate is then die-cut into individual systems and pouched.
From an appearance standpoint, the reservoir system resembles a large,
Band-Aid with an exaggerated “bubble” and the matrix system resembles a mere
flat piece of tape. These systems are illustrated in Figure 2.
As validation is similar for both systems, the remainder of this chapter
will concentrate on efforts to validate the matrix systems.
III. ESSENTIAL TRANSDERMAL
VALIDATION ELEMENTS
Transdermal system validation requires certain elements in order to be successful.
Some of these elements are planning, documentation, time, budget, resources,
quality, understanding, and communication. To illustrate how important
each of these elements is, they will be discussed one by one.
A. Planning
Planning is necessary for solid validations. Take, for example, an environment
in which key leaders know the importance of validation. All of a sudden responsible
parties are directed to conduct validation on the next three manufacturing
Figure 2 Diagram detailing differences between matrix and reservoir system.
Copyright © 2003 Marcel Dekker, Inc.
batches, so they simply prepare a cover document for the “validation” batches.
Is there any value in putting together a cover document that basically indicates
that the next three manufacturing batches will be dubbed validation batches?
What if one of the three has problems? Which courses of action will be taken?
Validation does not just happen; it has to be planned for. This is why planning
is a must in any successful validation program.
B. Documentation
Good documentation should capture the entire validation activity. If there is no
documentation, on what will you record your validations? Was the protocol
approved? Where are the necessary procedures? What happened in validation
event 2? How many samples were pulled in validation event 1? Each of these
questions supports the importance of documentation.
C. Time
No matter what kind of constraint is imposed, organizations must allow adequate
time for validation. At the very least, time must be allotted for some
degree of planning, for the requisite number of events planned to occur, and for
the gathering of the results. If the validating department has been given a “drop
dead” date for validation and if this date will not support the items mentioned
above, there is likely no need to begin validation.
D. Budget
What if a company has done a good job planning for validation, has put in place
adequate documentation, has sufficient time, but does not have funding to support
validation? It should be obvious that validation probably will not occur—
until funding has been provided.
E. Resources
Validation requires money, time, planning, and documentation. It also, however,
requires human resources to push the buttons, collect the data, submit the samples,
analyze the collected samples, summarize the reports, and gather the required
signatures. Most validations are very resource-intensive undertakings.
Somehow companies must assure that the requisite resources are available. Although
not recommended, these resources may be external (contracted laboratory,
consultants, etc.). With the exception of a qualified contract laboratory, the
Copyright © 2003 Marcel Dekker, Inc.
reason external resources are discouraged is that validation should always use
the validating company’s resources for execution.
F. Quality
Though CGMP validations require certain inputs from a quality department,
this is not the quality referenced here. Good validations improve quality. Good
validations result in quality. A good validation is quality. For example, a good
validation will represent a snapshot about the process or equipment. Typically
such a validation will have elements of process/product updates or historical
references for the item that has been validated, therefore the package(s) that
have been assembled have to possess a certain level of quality if the validation
is successful.
G. Understanding
Typically a validation exercise will involve representatives from multiple areas.
Those involved in a validation must possess a good understanding of the purpose
of validation; they cannot perform a thorough validation if this understanding
is lacking. Each of these representatives must have a good understanding of
why they are performing the validation and what constitutes success and failure.
They must embody the meaning and intent of validation. This understanding
will aide in assuring that a total team effort toward any common goal will be
expended.
H. Communication
The ultimate key to successful validation is communication—not just at the
development stage or the commercial stage, but throughout the entire product/
process development stage. Validation communications must occur on a plantwide
basis. Validation-related standard operating procedures (SOPs) should be
implemented, with each impacted operating department being required to approve.
This will stimulate department-to-department interest and ownership. It
is therefore very important that companies promote the importance of validation
through communication.
Consider an example in which validation (performance qualification) of a
utility system has been mandated. The responsible resources reluctantly charge
right in and begin validation. In the first week of testing, they uncover a sampling
point that is not accessible. The protocol has committed validation personnel
to collecting samples from this inaccessible point. If those responsible for
validation had communications with other plant personnel, they would have
Copyright © 2003 Marcel Dekker, Inc.
been advised that this site was not available. This is why communication is a
must for any successful validation.
IV. UNIT OPERATIONS AND MATERIALS/COMPOSITIONS
Now that we have discussed the elements of a good validation, we will pursue
one of those elements: understanding transdermal unit operations, as this will
be necessary before discussing transdermal process validations. We will start at
the beginning, with the acquisition of components and raw materials.
A. Material Ordering and Receipt
Of course requisite materials are first ordered. Upon receipt, these items are
placed in quarantine until they are tested against established specifications, meet
those specifications, and are finally released by the quality control laboratory.
A typical material/component flow diagram is presented in Figure 3. Once these
materials are released, they are usually used on a first-in first-out basis.
B. Dispensing Process
The CGMPs require that appropriate batch documentation be prepared for any
batch designated for manufacture. Following the raw material release step, specific
weights of raw materials are prepared as per batch/dispensing records.
Active drugs sometimes exhibit therapeutic actions that are typically harmful to
animals, therefore the weighing and dispensing of these actives are usually done
in an environmentally controlled chamber, which not only protects the active
Figure 3 Path of raw materials and components.
Copyright © 2003 Marcel Dekker, Inc.
from outside contaminants, but also protects the immediate surrounding environment
from the active.
C. Mixing Process
Dispensed materials are charged to a mix tank or mixer. These components are
then mixed under controlled conditions (e.g., time, agitation, temperature). Upon
completion of mixing, the resulting intermediate is sampled and then analyzed
by a quality department. While awaiting release, the intermediate is transferred
to one or more uniquely identified stainless steel transfer vessel(s) and held in
quarantine. Testing for release is against established specifications. This process
is illustrated in Figure 4.
D. Coating, Drying, and Laminating Process
The released intermediate is pumped from the stainless steel transfer vessels
through a slot (extrusion) die situated within the coater/dryer/laminater (coater).
The released intermediate, with active uniformly dispersed, is pumped through
Figure 4 Schematic of transdermal mixing processes.
Copyright © 2003 Marcel Dekker, Inc.
the slot die onto a release liner (typically of polyethylene) that is pulled through
the oven of the coater under controlled conditions (speed, temperature, and airflow).
Likewise, this coated liner is bonded to a backing film (typically of polyester
composition). The laminate resulting from this processing step is then
sliced (slit) lengthwise and wound into independent rolls appropriate for the
final system size. For example, if a square 25 cm2 system is under development,
chances are that the width of a roll would approximate 5 cm. This step is illustrated
in Figure 5.
E. Slitting/Relaminating Process
As seen in Figures 6 and 7, the final system has a tab that aides in commercial
system application. This tab is formed from the release liner by the relamination
step, which consists of placing a roll of laminate onto the slitter-relaminating
equipment. This roll is then guided through rollers where the release liner is
removed and slit (sliced) to the correct width. The slitted material is then placed
Figure 5 Schematic of transdermal coating process.
Copyright © 2003 Marcel Dekker, Inc.
Figure 6 Schematic of overlapped and slit section of laminate.
onto the adhesive surface of the coated backing film in an overlapping fashion.
The laminate with the resulting overlapped tab is then rewound.
F. Pouching Process
The rewound rolls of laminate are transferred to the pouching and die-cutting
equipment. The pouching process involves taking these slit and overlapped rolls,
cutting them into individual systems, and then finally sandwiching them between
two layers of poly pouch material.
The cut systems are placed on a conveyor and moved forward to a pickand-
place station from where they are placed on a bottom pouch layer. The
Figure 7 Typical transdermal matrix system with overlap tab.
Copyright © 2003 Marcel Dekker, Inc.
bottom pouch layer may be printed with the lot number and expiry date prior to
being cued for the cut systems. The top pouch layer is sealed to the bottom
pouch layer containing the systems. Of course the sealing occurs under controlled
conditions. Preprogrammed bar code scanning equipment may also be
used to verify the correctness of the bar code during this process. In addition,
sensors that detect the presence of the systems in the sealed pouch may also be
used.
Sealed pouches are then transported to the slitting and shear stations where
each individual pouch is cut. The systems are then conveyed through an accept/
reject station where rejected material is discarded. The systems are sampled,
tested, and released by the quality groups against preapproved product specifications.
Upon quality control release, the individually pouched systems are collected
for final packaging. This process is illustrated in Figure 8.
Figure 8 Schematic of transdermal pouching process.
Copyright © 2003 Marcel Dekker, Inc.
G. Transdermal Packaging Process
At the transdermal packaging stage, multiple pouched and released systems are
placed into the company’s specified packaging, which of course results from
marketing studies. The packaging operation is validated to demonstrate and establish
that
1. The correct number of released units are consistently placed in the
package.
2. Packages with empty pouches are rejected.
3. Only acceptable cartons are kept.
4. Only systems reflecting the correct bar code are packaged.
Finished packaging is of course subjected to the routine battery of quality control
testing.
V. WHAT DOES TRANSDERMAL PROCESS
VALIDATION INVOLVE?
Assuming that each validation element is present and possesses a better understanding
of the unit operations, we can now discuss some of the areas that
require attention as part of transdermal process validations. Most process validations
performed in a CGMP environment should involve the items listed in
Table 1.
Is transdermal process validation any different from other CGMP validations?
What measures are involved in this particular validation? What is the
objective? Let us now explore and answer each of these questions.
A good transdermal process validation will also involve the components
listed in Table 1. Transdermal process validation is therefore no different from
validation for any other product or process. All of these things must undergo
some form of validation to assure that the objective is met—that the end product
is manufactured under a stable and consistent process and is therefore fit for
Table 1 Components Included in CGMP
Process Validations
Facility Environment
People Analytical laboratory
Raw materials Equipment
Procedures Process
Copyright © 2003 Marcel Dekker, Inc.
commerce. It is typically a given that the facility has been adequately validated,
therefore our focus will be directed on the other items contained in the list.
A. People
Hopefully it is clear why the people aspect must be included in any transdermal
process validation plan. One reason is that even highly sophisticated equipment
cannot program itself, meaning a human element has to be involved. Wherever
people are involved in a validated process, therefore, appropriate measures must
be made to “validate” their roles. How is this done? Typically, people employed
in CGMP environments undergo rigorous training programs that will assure that
they do their tasks consistently. One notable program is the SOPs, which is
nothing more than a documented method by which key activities are performed.
These procedures are written and approved and must be followed to assure that
the people involved repeat their actions on a consistent basis. Of course, personnel
are trained and certified on each SOP that impacts their particular area(s).
B. Raw Materials
Raw materials—or starting materials—are crucial to the end quality of any
final product. Is it too much to ask the vendors to validate their raw materials?
Are the drug manufacturers able to pay the cost associated with vendor-validated
materials? Short of material validation, what measures are then taken to assure
that the materials used possess the desired quality? How do we assure they are
produced under robust manufacturing processes?
While it may be acceptable to expect vendors to validate their raw materials
given today’s regulatory environment, reality suggests that the cost of the
validation effort will not be borne by the vendor alone. Logic suggests that in
most cases the extra cost would be added to the product and passed directly to
the consumers. Logic also suggests that the extra cost shouldered by the consumers
will be directly dependent upon the complexity of the vendor’s validation
program.
The assessment of material quality normally starts with comparing a material’s
attributes to the specifications established by the purchasing company.
Once the material satisfies established specifications, efforts are made to assess
the stability of the product or intermediate manufactured with the material. Typically
the determination of raw material process stability is made during the
product development activities. Once a vendor or vendors have been selected,
three distinct vendor lots of a given raw material will be purchased. Development
batches of the product are then produced using these lots, and samples
from the three batches are placed on stability. The thought is that if the materials
from the three lots result in product with suitable stability profiles, the raw
Copyright © 2003 Marcel Dekker, Inc.
material(s) and the manufacturing process(es) are valid. Although not the perfect
method of “validating” raw materials, this has been satisfactory in the past.
C. Procedures
The CGMPs require that production procedures be written for any support activity
that is repeated within a CGMP environment (21 CFR Subpart F-Production
and Process Controls, “Written procedures; deviations”). Why is this true? Simply
because validation is about proving that something performs the same task
in a consistent manner. Validation requires consistency. Likewise, procedures
that are followed assure consistency. It should therefore be no surprise that
operational procedures are written and executed repeatedly. The ultimate test
for the validity of written procedures is the acceptability of the final, validated
product.
D. Environment
Environmental validation entails proving and documenting that each room in
which a CGMP activity occurs has the appropriate conditions. This entails monitoring
and evaluating room pressure, temperature, humidity, viable organisms,
and nonviable particulate counts. No in-depth discussions are planned around
this particular topic, as it has been addressed numerous times in other publications.
E. Analytical Laboratory
In the case of the laboratory, what is its function relative to the transdermals
manufactured under CGMP? Generally the laboratory is where the various
methods used to evaluate the attributes of a given transdermal or intermediate
are developed, qualified, and validated. Many of these methods can often be
adapted directly from the USP. If a special non-USP-derived method is required
to evaluate a transdermal product, then the company is obligated to demonstrate
and document that the method selected is valid. The validity of the method is
determined by a thorough evaluation of the following parameters [3]:
Precision
Accuracy
Specificity
Limits of detection and quantitation
Linearity and range
Ruggedness
Robustness
Copyright © 2003 Marcel Dekker, Inc.
Often the equipment used to run the analytical methods must also undergo
some type of qualification. It is suggested that installation qualification activities
be performed at the very least. Many laboratory methods must undergo a “calibration”
before each use, which can serve to eliminate the need for operational
and performance qualifications. Again, all of the related analytical calibration/
qualification/validation activities performed must be documented.
F. Equipment
Equipment qualification typically entails installation qualification (IQ), to demonstrate
that the equipment is indeed what was specified; operational qualification
(OQ), to demonstrate that the equipment performs acceptably over its design
range; and performance qualification (PQ), which demonstrates that the
equipment renders consistent performance. No time will be spent providing formal
definitions for these terms.
Why perform IQ? Why perform OQ? What about PQ? In upholding the
intent of validation, it is very important that companies understand the roles of
IQ and OQ. Examples will be used to convey the importance of these three
qualification phases.
Assume that a very successful company produces 1000 transdermals per
day. Due to market demand, its manufacturing department is instrumental in
purchasing a new piece of equipment that will reportedly yield 1500 transdermal
systems per day. Manufacturing requests facilities to remove the old piece of
equipment and install this new piece of equipment. Upon installation, manufacturing
attempts to use this new piece of equipment and finds that it won’t run
continuously—it only runs for 1 hr and then shuts down. In addition, manufacturing
has also found that the equipment is only capable of running at 75% of
its reported production rate.
After spending weeks performing an intensive investigation, technical services
finds that the equipment manual for the piece of equipment (which was
still with the vendor) has a disclaimer that plainly states that the equipment must
undergo a 3-month break-in period during which the rate of production is 60–
80% of the final production rate. Further, this manual also states that the equipment
must be lubricated once an hr for the first month. If not lubricated, the
equipment will shut down.
How would performing an IQ have prevented this from happening? One
of the purposes of the IQ is to acquaint the purchaser with the newly purchased
equipment. It is a mechanism for establishing and documenting that the equipment
ordered is what was desired. It should have required that the equipment
manual be received and on file within the company. A good IQ program would
have also required that certain maintenance activities be performed on the equip-
Copyright © 2003 Marcel Dekker, Inc.
ment and that the necessary preventative maintenance activities be entered in
the company’s PM program.
How would performing the OQ have helped avoid some of the problems
encountered with the new piece of equipment? Well, for one thing, the OQ
would have uncovered the true rate of production (although this should have
been uncovered in the IQ by reviewing the equipment manual), which sometimes
differs from the claimed rate.
Assume that the new piece of production equipment is operating without
incident for a year or more. The vendor used brand name parts for the piece of
equipment but went bankrupt. All of a sudden, a key part on the equipment
breaks. For some strange reason, facilities cannot figure out the part number.
Unfortunately, there is no documentation because there was no IQ performed,
which would normally detail the spare parts and of course part numbers and
drawings.
The PQ phase is as important as the IQ and OQ phases, as it serves to
establish that the equipment is capable of performing its activity on a consistent
basis. This phase may be viewed as a transition phase to the actual validation
phase.
G. Process
The transdermal manufacturing process is typically validated after the equipment
qualification steps have been successfully completed. A good process validation
requires each of the preceding validation steps be done successfully.
Given that they are successfully completed, the full-scale process for manufacturing
the transdermal is run three consecutive times. All formal SOPs (production,
laboratory, warehouse, etc.) that affect the transdermal product must therefore
be effective and referenced throughout process-validation activities.
VI. MATRIX TRANSDERMAL SYSTEM
EQUIPMENT QUALIFICATION
As with other forms of regulated drug products, transdermal manufacture requires
that all major equipment be qualified. Major equipment may be defined
as equipment having adjustable features or controls that makes direct contact
with the product during the production process. The qualification activities performed
for major pieces of equipment associated with the manufacture of matrix
transdermals will be discussed in this section. Major pieces are captured in
Table 2.
As an example of the types of activities that constitute qualification, we
will take the slot dies and detail IQ and OQ requirements.
Copyright © 2003 Marcel Dekker, Inc.
Table 2 Major Equipment Used in Matrix Transdermal
Manufacture and the Normal Qualifications Required
Equipment IQ OQ PQ
Glove box x x N/A
Mixer x x x
Transfer pumps x x x
Transfer vessels x x N/A
Coater/dryer/laminator x x x
Slot dies x x N/A
Slitter/relaminator x x x
Poucher x x x
Packaging equipment x x x
Note: All equipment to be included in process validation.
A. Slot Die IQ
Of course the first item that should be documented for this equipment is the
vendor. Other key items will be the dimensions, materials of construction, and
any identifying numbers contained thereon. All of this information should be
documented in the IQ protocol.
B. Slot Die OQ
Here, if any mechanical function can be performed with the subject item, its
range should be evaluated if that range is important to the equipment owner.
For example, if the slot die has two removable pieces, the fact that they can be
disassembled and reassembled should be challenged, if it has an adjustable
opening, this should be challenged, and so on. All findings or protocol results
should of course be documented.
Although the IQ and OQ are typically not repetitive steps, they are very
important because they provide the foundation for the subsequent validation
steps. They then require good documentation and also establish a certain level
of trust and confidence with the equipment. The documentation serves as a
snapshot or record of the equipment as it is received from the vendor.
It is extremely important if timing and budget permit to perform a trial
study on any test condition referenced in the OQ or PQ documents. This is
especially true for major pieces of equipment, such as a mixer or coater. The
reasoning is that if a test condition cannot be achieved during formal qualification,
a deviation and an explanation will be required, thereby increasing the
documentation requirements.
Copyright © 2003 Marcel Dekker, Inc.
These trials also increase familiarity with the equipment, but in addition
to these benefits, the work done in advance of the formal program will typically
eliminate the need for some of the work on the tail end of the activities. This is
illustrated in Table 3.
VII. MATRIX TRANSDERMAL SYSTEM
PROCESS QUALIFICATION
Assuming that the equipment qualifications have been successfully completed, the
focus can now shift to the transdermal PQ, which consists of multiple pieces.
These necessary processing pieces are illustrated in their proper order in Figure 9.
Of course these pieces or steps begin in development with initial processdevelopment
activities and conclude with product commercialization. All preprocess
validation activities—from the initial ranging studies to the processspecific
validations—can be dubbed as PQ activities, since they create a certain
level of comfort with the process. These activities typically involve more than
three full-scale runs—the number usually associated with validation. How exactly
does this work? How can a qualification require more runs than a validation?
The answer is very simple; validation includes qualification, which means
Table 3 Benefits of Prequalification Activities
Prevalidation activities Postvalidation activities
Phase recommended potentially eliminated
Installation Review purchase orders, design Need to write deviation reports,
qualification specifications, equipment man- protocol, amendments, etc.
uals, familiarization with subject
equipment
Operational Perform “trial” OQ to confirm Need to write deviation reports,
qualification ranges protocol amendments, etc.
Performance Perform abbreviated PQ “trials” Need to abort/revise/reissue protoqualification
to confirm equipment perfor- col or write deviation reports,
mance protocol amendments, etc.
Cleaning Perform abbreviated cleaning “tri- Need to revisit/revise cleaning
validation als” to confirm ability to clean procedure, abort/revise/reissue
acceptably protocol or write deviation reports,
protocol amendments,
etc.
Process Preceding activities Preceding activities
validation
Copyright © 2003 Marcel Dekker, Inc.
Figure9 Order and responsibilities for process activities supporting transdermal process
validation.
that all of these steps support the actual validation. All of these steps are required
to provide the needed level of comfort mandated by the regulatory environment.
Again, these activities may be more or less than those conducted by
other firms.
Figure 10 lists certain notable equipment and process activities used to
assure a sound transdermal process validation and the recommended sequential
order of execution. Let us review the listing of these activities and then examine
in some detail the process functions that should be conducted.
A. Maxtrix Transdermal System Process-Ranging Studies
Assume that a basic process has been identified to produce a newly developed
product on a small scale. As this process is in its infancy, operating ranges are
unknown. Looking back at Figure 9, we see that process-ranging studies are
conducted in development. What exactly are these studies? Before discussing
what these studies entail, we must first define the critical process parameters.
Critical process parameters are those controllable parameters that if left uncontrolled
may have a negative impact on product quality. Some examples of
critical process parameters are temperature, mix speed, and mix time for mixing;
oven temperature, airflow rate, and web speed during the transdermal coating
process; and heat seal temperature and heat seal pressure during the product
pouching process. There are of course others that will be discussed later in this
chapter.
Copyright © 2003 Marcel Dekker, Inc.
Figure 10 Related activities for transdermal process and equipment validation.
Copyright © 2003 Marcel Dekker, Inc.
It is extremely important to understand that these parameters have an effect
on the physical and chemical quality of the product. This effect is simulated
in Figure 11.
Figure 11 is symbolic of the relationship between parameters and product
attributes. For example, if the temperature is varied during product manufacture,
the viscosity, assay, and homogeneity may be affected. The same is true for
agitation speed and agitation time.
The best place for the determination of critical process parameters for any
new transdermal process is during product/process development. Why is this?
One reason is that this will minimize the time spent trying to validate the fullscale
commercial process. In thinking about validation and assuming that the
approach will be held to the widely accepted three-run rule, a common question
should be how to accomplish true validation of a variable process with only
three repetitions. Most manufacturing processes have not only a defined operating
target value, but also a range of operation. For example, many manufacturing
processes have a target mix temperature of t degrees, with a range of t ? x
to t + x. Realistically, it should require a minimum of nine events to gather
validation data for a process with only a single variable. How can an organization
“validate” the true process range in only three successive events? This is
where process-ranging studies often fill the void left by most process validations.
Process-ranging studies involve operating the process at the extremities of
its parameter ranges. For example, if you have a process that is operated at a
temperature of 60–70°C, process ranging would entail data gathering at these
points and the target, which should be 65°C. The same is done for each critical
parameter.
As mentioned above, special studies such as range-finding studies are typically
conducted during the development process. These ranging studies establish
the limits for the critical parameters [4]. A statistical tool called design of
experiments [5] (DOE or factorial design) is invaluable during such studies.
Figure 11 Typical relationship between process parameters and product attributes.
Copyright © 2003 Marcel Dekker, Inc.
The objective of such experiments is to identify acceptable process parameter
ranges that result in the product meeting established specifications. If designed
and used properly, these studies usually decrease the number of runs required
to thoroughly evaluate the critical parameter limits. What must first be established
is that the target identified will actually produce good product. Briefly,
assuming there are three critical parameters, a DOE would involve 8 (23) runs.
These eight runs will involve the extremes of each of the critical parameters
and will actually mix these extremes. For example, high (+) temperature will be
mixed with low (?) mix speed and low (?) mix time, high (+) temperature will
be mixed with high (+) mix speed and low (?) mix time, and so forth. This is
illustrated in Table 4, with the + indicating the upper range limit for a particular
parameter and the ? indicating the lower range limit.
This same pattern would be repeated for each of the other unit operations—
coating, pouching, and packaging. If the resulting product does not meet
the specifications, then additional experiments should be done until the point is
reached for each parameter that delivers acceptable product. In all cases, the
operating range must be narrowed to reflect the point at which acceptable product
results. Figure 12 summarizes the decisions that should be made following
a given development experiment.
Although this exacting statistical mode of evaluation could conceivably
involve more than eight total runs for each unit operation, it is a much more
desirable starting place than the trial and error method used in the past.
Product attributes, which should also be identified early on in the product
development phase, come into play during the assessment of the parameter values.
What exactly are product attributes? In simple terms, these are those specifications
that must be satisfied in order for the product or intermediate to be
Table 4 Typical Design of Experiments for Transdermal
Process with Three Critical Parameters
Run Mixer Mixer Mixer
numbers temperature agitation rate agitation speed
1 + + +
2 + + ?
3 + ? +
4 + ? ?
5 ? + +
6 ? + ?
7 ? ? +
8 ? ? ?
Copyright © 2003 Marcel Dekker, Inc.
Figure 12 Decisions resulting from developmental transdermal ranging experiment.
acceptable for release to the next phase. For example, if a mix solution has a
final attribute of viscosity, then it should be assessed during each of the planned
runs. If any one of these runs results in an out of spec viscosity, then this is a
signal that some or all of the parameter limits require adjustment. In a welldesigned
and -executed DOE, any combination of parameter limits resulting
from the study will yield acceptable product attributes. If the opposite is true,
this is a clear indication that some of the limits require adjusting.
If properly documented, the results of these studies can be summarized
and made available to auditing bodies. Such studies serve to complement the
full-scale validation work that is done. In the absence of such studies, companies
may find it necessary to explore range extremities during full-scale process validation.
Given the fact that the ranging studies have been successfully completed,
attention is focused on the next process qualification step—Scale-up studies,
demonstrations, and Trials.
B. Scale-Up Studies, Demonstrations, and Trials for Matrix
Transdermal Systems
As we know, a critical step within the development cycle of any new product
or process is the scale-up step. At this particular point, it is very important that
adequate communications have occurred between the group responsible for the
product development and the group charged with process validation. Actually,
in many organizations, the process/product development department shoulders
the responsibility for product scale-up and then “transfers” the technology to
manufacturing for product commercialization [6].
Copyright © 2003 Marcel Dekker, Inc.
In some environments, scale-up is handled jointly by development and
departments proficient in full-scale manufacture, such as technical services and
process engineering and in some cases manufacturing. If a process has been
well developed in development on subcommercial-scale development equipment,
how does one assure that this same process is delivered on full-scale
commercial equipment? What affect does equipment scale have on the process?
Is it safe to assume that since developmental-scale equipment delivered acceptable
performance it will perform likewise at commercial scale? Probably not.
This is the reason most progressive companies perform what is termed demonstrations
on full-scale equipment.
Typically, the first full-scale events are demonstrations. Some scale-up
studies may be performed at full scale just before the formal demonstrations are
initiated, however. This would be true in those cases in which the results of the
development-ranging studies do not provide sufficient confidence or assurance.
In addition to providing assurance that the process can be duplicated at full
scale, demonstrations provide a platform for operator training, SOP development,
laboratory method fine-tuning, equipment cleaning, and most important,
site experience with the demonstrated process. It should be noted that most
companies are constrained by a budget for product development, which means
that they cannot afford doing a battery of demonstrations.
1. Why Trials?
It is recommended that firms conduct trials on commercial-scale equipment during
process scale-up. Think back to the very first day an airliner went commercial;
in other words, the very first time an airliner loaded up customers and flew
them from point A to Z. It is reasonable to think that this maiden flight was
made without any trials? Absolutely not. Without being intimately familiar with
the airline industry’s practices, it would probably be safe to assume that the
very first commercial flight with passengers was preceded by a minimum of
three trials—trials to assure that the plane would ascend and descend at the
pilot’s commands, trials to assure that the craft would stay in flight with a full
load, trials to assure that cabin pressure would be maintained, and so on. It
would also be safe to assume that each of these challenges was designed to
represent worst-case or stress testing. For example, if an airliner was designed
to carry a 2-ton load of comfortably, it is very likely it was tested with 2000 lb
plus some safety factor. These same principles apply to validation.
2. The Benefit of Trials
Let us now examine the role of trials in a CGMP environment. Cleaning validation
will be the model used to illustrate the need for trials. In accordance with
subpart D of 21 CFR, Section 211.67, equipment used in manufacturing trans-
Copyright © 2003 Marcel Dekker, Inc.
dermals must undergo routine cleaning. Cleaning validations are done to demonstrate
and document that residues of drug(s) and/or excipients or cleaning agents
remaining on the equipment used to manufacture transdermals have been reduced
to acceptable levels. During process scale-up activities and before cleaning
validation, equipment cleaning trials are recommended [7]. Why? Simply
because these trials provide an unofficial arena to firm up full-scale equipment
cleaning, to test the cleaning limits, and to provide preliminary training to the
operators, the samplers, and the analytical laboratory. Cleaning trials are a
means of providing assurance that the cleaning procedure is ready for validation.
They also serve to identify areas in which the heaviest residues are found. This
is done by “stress” sampling, or sampling in every potential point that may
represent the worst case. During stress sampling or cleaning trials, the sample
points identified will typically exceed the validation sample points, which will
of course typically exceed routine commercial sample points. This is illustrated
in Figure 13.
Trials beg the validator to become creative. During the cleaning trials for
the casting solution, one batch of scale-up solution is used to simulate three
successive mix tank cleaning trials. The solution is charged in, agitated at maximum
mix speed (to induce splashing) for a specified amount of time, and discharged
from the tank. The tank is then allowed to sit for a specified amount of
time (equal to the anticipated maximum window between tank use and cleaning).
Once the time limit is reached, tank cleaning is initiated. The previously
Figure 13 Simulation of sample point reduction from transdermal trial to validation
to commercialization.
Copyright © 2003 Marcel Dekker, Inc.
used batch of casting solution is then charged back into the tank and the cycle
is repeated.
It is important that the stability of the active be assured over the preliminary
trials, therefore efforts are made to ascertain that the potency of the casting
solution is unchanged throughout the planned trials. This is true because if the
casting solution loses its potency over the course of the trials the analytical
results may be skewed.
Trials typically use worst-case or stress sampling to determine the highest
residue. It is suggested that once residue loading has been identified over the
course of at least two cleaning trials, validation sampling be such that the highest
residual load be sampled (Fig. 14). Once the validations have been completed,
it is typically acceptable to further reduce the number of sampling locations
as shown in Figure 14. In Figure 14, cleaning trials started out with nine
sample points. In validation, these sites were narrowed down to five. Finally, in
commercial mode the sample sites have been reduced to one. Again, these are
only examples. Oftentimes the laboratory supporting cleaning validation can
only analyze a limited number of samples, meaning that true stress sampling
may not be done. In any event, sound logic should be used to pinpoint sampling
locations.
Another good reason for cleaning trials is that during cleaning validation,
every event should be performed in the absence of problems. Any failures encountered
with the validation will have to be investigated and explained away,
meaning that time must be expended by people to identify, review, and docu-
Figure 14 Simulation of sample results from transdermal trials to validation to commercialization.
Copyright © 2003 Marcel Dekker, Inc.
ment the reason(s) why the failure occurred. These trials provide a way to flush
out and eliminate any potential problems with the cleaning procedure before it
is subjected to validation. Finally, perhaps the main reason for performing these
trials, is that the risk of losing multiple full-scale batches as a result of batch
contamination is very much reduced.
3. Recommended Documentation for Trials
The same reasoning applies to other processes pending validation. During any
trial, a “draft” protocol very close to the final validation protocol to be used
should be assembled. This draft document—or any trial or draft document—is
not intended for FDA review. It is simply a means for data gathering and employee
training. Any trial document should be created independently and kept
separate from documents supporting other activities, meaning that separate activity-
driven documentation needs to be prepared and maintained. Separation is
recommended because if FDA, for example, wants to dig deeper into the “process
demonstration” documents, data supporting cleaning validations (specifically
cleaning trials) will not be revealed unless asked for.
C. Process-Specific Validation for Transdermals
Developmental activities that include ranging studies, scale-up studies, demonstrations,
and trials certainly aid in establishing ranges of operation for critical
transdermal process-control parameters. Is it safe to assume that just because
measures have been taken to gather this information on the critical processing
parameters formal process validation will be a success? One of the very first
steps toward process validation is to plan for the activities. First of all, there
must be a supporting structure in place for any validations performed; a validation
cannot exist in a void or vacuum. Are adequate validations procedures in
place? Has the existence of a solid internal document maintenance program
been assured? What about validation change control? Is it set up to track all
changes to equipment that has been installed? What about training in general—
are there formal procedures? Equipment maintenance? Instrument calibration?
Is the equipment to be used newly acquired? If so, has it undergone requisite
IQ, OQ, and PQ activities? If so, how good are the completed packages?
Before the equipment was received from the vendors, were vendor equipment
qualifications (also known as factory acceptance tests—FAT) conducted and
were the results satisfactory? Are there any outstanding issues requiring resolution?
Some assumptions will of course be made. These assumptions are listed
in Table 5.
All activities identified in Table 5 should occur prior to beginning process
validation. The economic environment of most drug companies is such that no
Copyright © 2003 Marcel Dekker, Inc.
Table5 Prevalidation Assumptions for Transdermals
Sound development package in place
Ranging studies completed and documented
Facility qualification completed and documented
Equipment qualification completed and accepted
Appropriate analytical methodology implemented and validated
Personnel training completed and documented
Process trials and demonstrations executed and documented
Change control in place and effective
All supporting documentation (validation SOPs, demonstration documents, etc.) in place
Appropriate operating procedures (manufacturing, maintenance/preventative maintenance,
cleaning, etc.) in place
Document maintenance (number, filing, retrieval) in place
more than three full-scale events are conducted. A progressive process validation
program that will involve each major unit operation and end with the formal
process validations is recommended for firms that can afford such endeavors,
however. Such studies build progressive confidence in the processes. These
studies typically prove to be an invaluable insurance policy for firms as they
undergo regulatory audits.
Individual process validations or process-specific validations—mixing,
coating, pouching—performed prior to formal transdermal process validations
are a way to build this confidence and are strongly recommended. True to the
term, these validations should be done on three successive events in each major
unit operation. Formal validation etiquette is used (preapproved protocols, trainings
confirmed, operating procedures in place, etc.). As an example, during the
mixing operation the mix time and mix RPMs should be monitored periodically
(kept under control) to assure consistency of the operation. Sufficient samples
of the casting solution should be collected upon completion of each batch and
used to establish uniformity. It is recommended that sampling be done in duplicate.
The secondary or duplicate samples serve as backup samples and are invaluable
in case something happens to the primary sets.
Parameters tracked during the mixing validations are detailed in Table 6.
Of course the equipment must operate within the acceptable ranges during the
validation event.
The product or intermediate resulting from the mixing step must satisfy
established specifications that represent the step’s product attributes. Some
mock attributes are shown in Table 7.
The coated product (the cast-film laminate) is treated as an intermediate.
In reality, significant efforts should be expended during the product’s develop-
Copyright © 2003 Marcel Dekker, Inc.
Table6 Mixing Parameter Targets and Ranges
for Transdermals
Parameter Target Acceptable range
Mix time (min) x x +/? y
Mix speed (RPM) x x +/? y
ment to show correlation between the coating weights and final product attributes.
It is recommended that during developmental work for the coating process
each lane be identified and each laminated roll be labeled. As these rolls
are formed during a given shift, labels should be placed strategically on the roll
to indicate the time of day the laminate is coated. A sampling pattern to gather
uniformity information is recommended involving beginning, middle, and end
of shift sampling, and left side, center, and right side of coating oven. Any
samples collected should be analyzed against pouched product specifications.
The results of this study can then be used to justify eliminating formal coating
product specifications at this coating stage in favor of a straightforward, periodic
in-process coating-weight test.
During the coating process, controlled conditions and coating weight
should be monitored periodically by the operators to assure that the environment
is appropriate to reduce the content of residual solvents and to attain proper
curing. The thickness of the casting solution layer should be controlled and used
to assess the final quality of the systems manufactured.
Of course, equipment parameters should be tracked during the process.
Mock parameters that can be tracked during the transdermal coating process are
listed in Table 8.
During the pouching process, operators should perform routine monitoring
of heat seal temperature, heat seal dwell time, and heat seal pressure, and at the
same time check the integrity of the sealant layers. It is recommended that
Table 7 Mixing Mock Specifications for Transdermals
Attributes Specifications
Appearance Brown viscous solution
Identity Matches retention time of reference standard
Assay x mg/g (x +/? y mg/g)
Percentage nonvolatiles ?x%
Copyright © 2003 Marcel Dekker, Inc.
Table8 Coating Parameter Targets and Ranges
for Transdermals
Parameter Target Acceptable ranges
Web speed (FPM) x x +/? y
Oven temperature (°C) x x +/? y
pouched systems be analyzed from the beginning, middle, and end of the batch
to demonstrate process consistency. Recommended pouching process parameters
to be monitored are listed in Table 9, with mock specifications listed in
Table 10.
Additionally, in-process pouch integrity testing should be performed periodically
during each pouching event to assure that the pouching process is consistent.
Maintaining any of these individual unit operations within the stated process
parameter ranges of course, demonstrates adequate process control. As with
any validation, any deviation outside the acceptable range requires investigation
and documentation.
D. Potential Problems and Recommended Resolutions
with the Matrix Transdermal
Problems exist for established processes, so is there any surprise that they are
encountered during the early stages of process development? Surely not. It
should be noted that all problems identified must be eliminated or resolved prior
to transdermal validation. Validation is not just an exercise done to satisfy FDA
or others in the auditing environment; it should be done with the goal of proving
that a process is under control. If there is sufficient evidence that a process is
Table 9 Pouching Parameter Targets and Ranges for
Transdermals
Parameter Target Acceptable ranges
Heat seal dwell time (sec) x x +/? y
Heat seal pressure (psi) x x +/? y
Heat seal temperature (°F) x x +/? y
Copyright © 2003 Marcel Dekker, Inc.
Table 10 Pouching Mock Specifications for Transdermals
Attributes Specifications
Drug release ?x% @ y time
Drug assay x mg/g (x +/? y mg/g)
Release liner peel force x g
Residual solvents Solvent X, ?x ppm: Solvent Y, ?y ppm
Area dimensions (system) x mm L: y mm W
Percentage nonvolatiles ?x %
not yet under control, there is no reason to strain or drain a company’s operating
budget. It is recommended therefore that all issues be addressed during product
scale-up. Actually, development is where the product/process cause-and-effect
relationships are learned, which means that not only are problems realized, but
also potential solutions.
Some examples of typical problems encountered with the matrix transdermal
systems and the corresponding potential solutions used for these problems
are identified in the following table.
Potential Matrix Defects
Stage Problem Potential solution(s)
Mixing Poor solution uniformity/solution Increase agitation time
not homogeneous. Increase agitation rate
Coating Poor laminate (product) uniformity. Adjust coating rate
Adjust mixing (parameters)
Product weights too high/low. Adjust slot die gap
Adjust coating (oven) temperature
Residual solvents too high. Increase coating (oven) temperature
Increase airflow
Decrease coating weight
Decrease coating rate (web speed)
Drug content too low/high. Adjust coating weight
Improper coating weight. Adjust metering pump
Adjust slot die gap
Cross-web coating is inconsistent. Adjust slot die angle
Adjust slot die gap
Casting solution flow to the slot Increase nitrogen head pressure
die inconsistent.
Copyright © 2003 Marcel Dekker, Inc.
Potential Matrix Defects (Continued)
Stage Problem Potential solution(s)
Laminate not dried uniformly. Adjust configuration of supply air
flow nozzles
Pouching Poor pouch seal. Adjust heat sealing temperature
Adjust heat sealing pressure
Adjust heat sealing dwell time
Systems in seal. Adjust pick and place mechanism
Systems not picked up. Increase vacuum to pick and place
mechanism
Systems not placed in proper Adjust vacuum mechanism
pouch position.
VIII. TRANSDERMAL PROCESS VALIDATION
As established earlier, transdermal process validation is proving the way a transdermal
product or end result is made is legitimate. This proof should be established
before a product is marketed or put into commerce. What does this term
require? Actually, this section, though very important, will be very short.
Discussions thus far have established that product commercialization
should be preceded by a host of developmental runs (to include ranging studies),
a minimum of two process demonstrations on which cleaning trials are conducted
(cleaning trials are performed on both equipment and manufacturing
rooms utilized), three individual unit operation (specific) validations within
which formal cleaning validation is completed, and, three successive process
validation events, in which all factors affecting the process (applicable manufacturing
operating procedures, personnel, equipment, etc.) are challenged and documented.
How are these successive process validations conducted? This activity is
basically achieved by combining each unit operation in a singular protocol and
therein addressing every procedure and activity used to manufacture the end
product. This is illustrated in Figure 15.
To summarize, the number of runs actually supporting the validation of a
transdermal process with three unit operations—mixing, coating, and pouching—
should exceed 24, as can be seen in Table 11. If the developmental ranging
studies are performed on a process that has three parameters, this number
quickly jumps to a minimum of 42, assuming that all of the ranging runs were
a success. This of course does not include cleaning validation.
Why perform all of these batches during the scale-up and validation of a
transdermal process or of any process? One of the main reasons is the resulting
Copyright © 2003 Marcel Dekker, Inc.
Figure 15 Depiction of how process validation builds. UO = unit operation.
Copyright © 2003 Marcel Dekker, Inc.
Table 11 Sampling of Runs Required to Support Transdermal Process Validation
Full, commercial scalea
Process specific Development
Demonstrations unit operation Process Total runs
Event Ranging studies and/or trials validations validation (minimum)
Mixing 2n 2, minimum 3, minimum
Coating 2n 2, minimum 3, minimum 3, minimum 24
Pouching 2n 2, minimum 3, minimum
Total runs 6 (where n = 1) 6, minimum 9, minimum 3, minimum
Note: n-number of process parameters.
aIn certain cases, “development” ranging studies were completed on commercial scale.
progressive confidence in the process. Of course, one of the downfalls with this
approach is the drain on the validation budget. What must be understood is that
the route chosen by a company must be adequately justified and budgeted.
IX. VALIDATION DOCUMENTATION FOR THE MATRIX
TRANSDERMAL SYSTEM
A. The Protocol
Now that all of the activities that support process validation are in place or have
been performed, will the work and effort be appreciated by auditing bodies?
What measures can be taken to assure that they are? There is one other aspect
of transdermal validation that will increase the potential for the effort to be
appreciated. This element is the protocol. What exactly is a protocol? Who
should approve this document?
Planning is key in any significant undertaking—whether it is a family
vacation or a critical project within a Fortune 500 company. Transdermal validation
likewise requires extensive planning, but in the form of a protocol. For
the sake of clarity, the protocol is a bit more than a planning tool for validation;
it is actually the vehicle for achieving validation. It tells the audience “By the
way, planning has occurred for this transdermal activity, and we will validate
as follows—.” A validation protocol generally accomplishes the following:
1. It details the item or items (“subject”) undergoing validation.
2. It provides an objective and an overview of what is being done and why.
3. It will typically reveal how many successful batches must be performed.
Copyright © 2003 Marcel Dekker, Inc.
4. It discusses equipment used to process the “subject.”
5. It details critical process parameters, acceptance criteria, sample
points, and the test methods to be used.
Let us examine what a protocol should accomplish. During an inspection
of a given product or process, FDA will more times than not conduct a review
of the process validation protocol. As mentioned earlier, the process entails
everything used to manufacture the transdermal—procedures, personnel, methods,
documents, and so on. Given the fact that the protocol will likely fall under
FDA scrutiny at some point and that other documents used to complete the
validation may as well, it should be easy to understand that the process validation
protocol should be used to reference as many of these other supporting
documents as possible.
For example, most companies would rather reference their supporting documents
than have FDA ask whether or not a particular document exists. Further,
this practice will assure that the company has actually taken sufficient time and
prepared the document referenced. There are those companies that prefer to
voluntarily attach the documents rather than just reference them. This may not
be in the best interest of CGMP manufacturers for two clear reasons. First,
attaching every development report, every batch record, every analytical
method, every support protocol/report and so forth will make a process validation
document—a hefty document to begin with—too big to read. Second, volunteering
any information is considered very dangerous, as it is very rare for a
company to have no dirty laundry. Why hang it out for FDA or any audience
to see?
Therefore, the recommendation is that the process validation document be
used as a guide document, referencing support documents as appropriate, as
illustrated in Figure 16.
It should therefore be clear that the protocol is a key communication tool
not only for the owner, but also for internal and external auditing parties. As a
communication tool, the protocol should be capable of completely informing
the reader of every critical thing that happened—from beginning to end—within
the activity.
What, then, are the specifics that should be reflected in a protocol designed
for transdermal process validation? Perhaps a better question is what is
the basic format of a protocol to be used in transdermal process validation. Let
us start with the second question and establish the vehicle to be used for validating
a transdermal process.
1. Format: Basics
As mentioned above, the protocol should reflect the item on which validation
will be performed. It should have an identifying code for easy retrieval. Pages
of the protocol should reflect the protocol title and the identifying code in the
Copyright © 2003 Marcel Dekker, Inc.
Figure 16 Schematic detailing how process validation document references other support
documents.
header or the footer; likewise it is recommended that the page number be in the
format of “Page x of y” and not “Page x,” as the former will give information
as to the total number of pages included. Some of the major parts are detailed
below.
2. Cover Sheet
A sample cover page is shown in Figure 17. This page is very important, as it
will identify what will be validated and provide the objective of the validation
activity. The objective is actually lifted from the body of the protocol. The cover
page briefly describes the major equipment required to perform the process and
the rooms in which the equipment is located. It will also list the identifying
document code and the persons (departments) who will be expected to approve
the document. In all cases, a quality representative must approve a protocol
constructed for validation. It is also recommended that a representative of the
department owning the validation subject be an approver, as should any lab or
support departments obligated to perform a task within the validation. Finally,
experience has shown that it is wise to have an executed protocol review box
resident on the cover page. (See Fig. 17.) The intent is that once the protocol
has been executed, someone who was not involved with execution must review
the document to ensure that all the I’s have been dotted and the T’s have been
crossed. This “reviewer” must be technically sound and familiar with the CGMPs.
In actuality, this review is simply to assure that everything that has been committed
to in the protocol has indeed been done, all of the comments are logical,
all of the conclusions are sound, there are no blank spaces, and so forth.
Copyright © 2003 Marcel Dekker, Inc.
PROCESS-VALIDATION PROTOCOL
DOCUMENT XYZ
Process Validation for Manufacturing of_ Transdermal Systems
Date (mm/dd/yy)
OBJECTIVE: To validate the manufacturing process for __ transdermal delivery systems by
verifying and documenting that the Mixing, Coating, Slitting, and Pouching processes
consistently yield product that meet commercial specifications. Three consecutive commercialscale
batches (theoretical yield: __ systems) will be manufactured. For each batch, final product
quality will be determined by comparing the analytical results to the established commercial
product specifications. Approval of the validation document summarizing this activity will
indicate that Technology Transfer was both successful and complete for this process.
EQUIPMENT IDENTIFICATION: Mixer manufactured by (vendor), with an approximate
volume of 20 Gallons; Coater/Dryer/Laminator manufactured by (vendor); Slitter/Rewinder
manufactured by (vendor); and, Pouching Machine (with Die Cutter) manufactured by (vendor).
Equipment numbers are identified in the appropriate section of this document.
ROOM IDENTIFICATION: ____ Mixing (Room #___), Coating (Room # ___), Slitting
(Room #___), and Pouching rooms (Room #___), all located in the manufacturing core at ___.
PREPARED BY
APPROVED BY
DEPARTMENT
DEPARTMENT
DEPARTMENT
DATE
DATE
DATE
(Preparer)
(Owner)
(Support Lab)
(Quality Group)
REVIEWED BY
Postexecution Review:
Figure 17 Recommended protocol cover page.
Copyright © 2003 Marcel Dekker, Inc.
3. Table of Contents
The table of contents is nothing more than a map of the document listing every
major section of the protocol and detailing page numbers.
It is recommended that the protocol be divided into three major sections:
Section I, which discusses the background and validation methodology; Section
II, which contains areas in which data collected during validation can be documented;
and Section III, a section for the various attachments that will be involved.
It should be understood that the contents of these sections may reside
in validation-specific SOPs. Even if appropriate SOPs have been created, however,
there is no assurance that the statements will be reflected in the execution
of the validation. Contents of each of these three sections are discussed in the
following sections of this chapter.
Section I: Background/Methodology. This section is the communication
part of the document. It is strictly instructional, providing history, how the validation
will be accomplished, and so on. There is no requirement for data entries
in this first section.
Objective. The objective states what the intent of the activity is. The
objective should be straightforward, yet touch on the underlying goal of the
activity. If the plan is to prove that a piece of equipment can be powered on,
this is the objective. If the intent is to demonstrate and document that something
is and does what it purports to be and do—to validate—then that is the objective.
One other suggestion is that the method of achieving the objective be
touched upon briefly. For example, if three events will be executed to prove the
objective, this fact should also be mentioned.
Scope. The scope section establishes the boundaries or limits of the validation
event. It identifies every major thing to be included by identification and
therefore excludes everything that is not a part of the event. An example would
be, “Validation will be done on the XYZ coater using matrix components xyz.”
This statement therefore excludes all coaters outside the XYZ unit and all matrix
components outside xyz.
Responsibilities. This section captures the responsibilities of the approving
departments prior to document approval. This way there will be no confusion
when a responsibility arises during or after the document execution.
Background. The background provides the reader with a bit of history
regarding not only what is being validated, but also why and how it is being
validated. Typically very little detail is provided in this section.
Process Descriptions. The process descriptions break down and define
every major process step. It should also discuss the processing sequence. For
Copyright © 2003 Marcel Dekker, Inc.
example, “the process entails dispensing, milling, blending, and tableting. The
mixing step involves taking the ingredients and agitating until—.”
Critical Process Control Parameters. The critical process control parameters
are those contollable parameters that have impact on the final product quality.
Parameter operating limits and the methods of assuring control of these
parameters within these limits are discussed in this section.
Validation Procedure. This section is devoted to telling the audience
how this particular validation will be achieved. This is actually where the validating
party conveys to the audience its interpretation of FDA’s expectations of
process validation. How many successful runs will be required? Three? Seven?
What if a failure is encountered? Hopefully, it is obvious how important this
particular section is.
Validation Methodology. The methodology section speaks to the areas
of documentation, protocol execution, and postexecution.
Documentation. Documentation addresses how the entries should be
made, the timeliness of those entries, and how to correct an incorrect entry.
Samples of items that should be addressed in this subsection are
This protocol provides spaces to record entries. All entries required should
be made and dated at the time they are performed. Questions that do not
apply should be marked “NA,” initialed and dated; all blank spaces should
be marked “NA”; large areas consisting of multiple blank lines should be
lined through and marked “NA.” Results generated in or related to this
activity should be properly documented and/or attached to this protocol.
Where testing is performed by a third party, the test report should be
attached to the applicable section of this protocol or included in the Validation
Report.
Even though most of this is obvious or is covered by an internal operating
procedure, it doesn’t hurt to communicate the expectations to the readers of the
document.
Execution. The execution section addresses courses of action during actual
execution. It mentions obvious facts about the items(s) to undergo validation.
An example would be: “The process for x transdermal systems has been
designed to consistently deliver satisfactory product. Challenges will therefore
be made to confirm that the equipment functions properly and yields product
meeting established commercial specifications.”
Postexecution. The postexecution subsection deals with the document
flow upon completion of the activity. An example is
Upon completion of the execution of this protocol, this document and all
related third party testing reports and engineering documentation are to be
Copyright © 2003 Marcel Dekker, Inc.
submitted to the validation project manager. A validation report summarizing
the results and including an explanation of all deviations from the procedures,
specifications, or acceptance criteria will be prepared. This report,
which will include a copy of the executed protocol, will be submitted to the
approvers of the protocol. Upon report approval, the original executed protocol
will be attached and submitted for internal maintenance.
Validation Sampling Plan. Any process undergoing validation must be
sampled. This section will tell the reader the logic that went into the sample
plan, the frequency of collecting the samples, the sampling locations, and so on.
Acceptance Criteria/Rationale. The acceptance criteria for each measurable
attribute (which can be lifted from the specification document) is important
and should always be shared. Likewise, it is recommended that a rationale be
provided for each criteria. For example, why must the final product moisture
content be 70–80%? What if it is 83%? The reasoning is that it is better to
consider this question before being asked by FDA during an audit, thereby
avoiding a situation in which the answer provided may not be the best.
Speaking of acceptance criteria, it is recommended that acceptance criteria
be provided not only for the final product, but also for the equipment used to
manufacture the product. The reason for this is that typically the equipment has
not undergone full process validation and therefore its performance must also
be evaluated.
Labeling. The labeling section simply discusses how labels will be prepared
and with what information. Typically the batch number, the validation
document number, the validation sequence or event number (run x of y), the
sample number (or other descriptive information; e.g., sample type and/or time),
and of course the date that sampling occurred are recorded on a validation label.
Conditions. The conditions subsection addresses the requirements for
timely approval of the document. A sampling is
If any subsection of the data documentation (Section 2) is incomplete or if
any deviation from the listed acceptance criteria is deemed unacceptable by
the signatories, then this document cannot be approved. If it cannot be approved,
timely activity closure is recommended and will require that all
outstanding issues are resolved to the satisfaction of the quality representative
or document termination with a cover note explaining the reasons for
the termination. In either case, the parties who approved the unexecuted
protocol must approve the resolution and/or the termination. Approval of all
protocol explanations is required prior to the approval of a revised protocol
generated to accomplish similar objectives.
Method of Analysis. In this particular section, some time is devoted to
addressing the methods to be employed in analyzing the samples collected. Typ-
Copyright © 2003 Marcel Dekker, Inc.
ically the actual validated method numbers—excluding, of course, the version
numbers—are identified. For example, if chemical residue analysis will be performed
using HPLC during validation, it should be identified by method name
and number (e.g., HPLC method xyz).
Qualification Verification. Again, the process validation protocol should
reference all items that support the validation: the procedures, personnel, methods,
and equipment. This section therefore lists and summarizes the various
installation, operational, and performance/process qualifications completed for
the equipment used in the process validation. These qualifications should list
each by equipment name and number and qualification and type. A typical verification
section is illustrated below.
Equipment qualification Performance/process qualification
Equipment Installation Operational Cleaning Ranging PLC Process
Equipment number qualification qualification validation studies qualification validation
Environmental
chamber ### ### ### ### N/A N/A ###
Mixer ### ### ### ### ### N/A ###
Transfer pump X ### ### ### ### N/A N/A ###
Section II: Data Documentation. Section II deals with the data documentation
aspect of the protocol. It is interactive and therefore requires entries on
the part of the executor(s). It captures critical variables of the validation activity,
such as lot numbers of raw materials used, equipment used, and batches produced.
It also captures process set points and observations as dictated by the
protocol. It is suggested that each page within the data documentation section
have a section devoted to the executor’s comments. Recommended sections are
detailed below.
Safety Awareness. Safety is critical for everyone involved with a validation
activity. This subsection addresses this issue, forcing the executors to acknowledge
their familiarity (via signature and by date) with all of the safety
aspects of the validation activity.
Required Determinations.
Training. To comply with CGMP guidelines, all persons involved with
the execution of an activity covered by the protocol must have been
trained on general CGMP and applicable internal procedures. This section
should require all persons involved to sign and date the protocol,
thereby indicating they have undergone appropriate training.
Copyright © 2003 Marcel Dekker, Inc.
Availability of standard operating procedures. This section requires the
executors to verify and list applicable operational, preventative maintenance,
calibration, and equipment cleaning procedures that are available.
Materials. This section documents each component (raw materials, laminates,
pouch stock, applicable lot/identifying numbers, etc.) used and
the identifying numbers for each batch manufactured under the protocol.
Sample Execution. This interactive section documents activity sampling,
and therefore provides proof that sampling did occur. Minimally, this section
will record the sample number (if appropriate), the sample type, the sample
time, and of course the individual who collected the sample. The value of this
section is often overlooked.
Results. The results section is where findings are documented for each
analysis. Although the acceptance criteria or specifications are listed in Section
I, it is a good idea to capture the acceptance criteria in the area(s) in which the
results will be listed, as shown in the next table. It is recommended that the
original data be kept within the responsible or analyzing department and that
the results be transcribed by the reporting laboratory to the protocol data sheets.
If the need arises to compare these two sources, they could be retrieved from
the data files of the responsible department.
Results: Event I
Resdual X Residual Y
Sample numbers acceptance criterion (?10 ppm) acceptance criterion (?30 ppm)
1
2
Conclusions. The conclusions section simply captures the overall results
of the activity. This section is typically completed by the executor or by someone
who is technically capable of reviewing the effort and rendering conclusions.
It should be concise and to the point, since the data are attached. What
exactly do the data tell the audience? Was the activity a success? If not, why
not? These are some of the questions that should be answered in the conclusions.
Section III: Data Attachments. This third and final section captures any
documents that lend support to the validation effort; for example, a report that
summarizes why a like-for-like substitution of a crucial piece of equipment
occurred during event 2.
Copyright © 2003 Marcel Dekker, Inc.
B. The Validation Summary
Although it might not be a very popular opinion within the industry, it is
strongly recommended that a second document be prepared that summarizes the
validation event. Why prepare the summary? It simply captures the overall outcome
of the validation and prevents the auditing body from having to thumb
through the protocol in search of the conclusions.
As does the protocol, the summary also has a cover page that lists the
protocol objectives and the conclusions—all on the front page. This document
should be approved by the same departments that approved the protocol. It
should also share the same identifying numbers as the protocol. A sample of a
summary cover sheet is shown in Figure 18.
Some other recommendations for the contents of the summary are addressed
in the following sections.
1. Summary
This section summarizes the validation activity, citing the fact that validation
occurred and for what purpose.
2. Discussion of Results and Deviations
This section discusses significant results and any deviations that occurred during
the validation. For example, if control of a critical parameter was momentarily
lost, a justification must be prepared explaining why it was lost and why this
lack of control is acceptable. If a sizeable justification is prepared, then it may
be wise to reference it in the summary and attach it to the validation report. The
same is true of any significant results.
3. Conclusions
As stated earlier, the conclusions capture the overall results of the activity. The
conclusions section should be concise. This section is lifted from the body of
validation summary and copied onto the cover page.
4. Future Activities
This section makes a statement about the revalidation activities for the process
and also states that any changes will be captured under the existing (validation)
change control system.
C. Validation Report
What constitutes a validation report? While it has been fairly well established
that the protocol is the planning tool and in some cases a communication tool,
it is recommended that the summary be used to communicate the outcome of the
Copyright © 2003 Marcel Dekker, Inc.
PROCESS-VALIDATION PROTOCOL
DOCUMENT XYZ
Process Validation for Manufacturing of_ Transdermal Systems
Date (mm/dd/yy)
OBJECTIVE: To validate the manufacturing process for __ transdermal delivery systems by
verifying and documenting that the Mixing, Coating, Slitting, and Pouching processes
consistently yield product that meet commercial specifications. Three consecutive commercialscale
batches (theoretical yield: __ systems) will be manufactured. For each batch, final product
quality will be determined by comparing the analytical results to the established commercial
product specifications. Approval of the validation document summarizing this activity will
indicate that Technology Transfer was both successful and complete for this process.
PREPARED BY
APPROVED BY
DEPARTMENT
DEPARTMENT
DATE
DATE
(Preparer)
(Owner)
(Support Lab)
(Quality Group)
CONCLUSIONS: The process for manufacturing __ transdermal delivery systems has been
validated by executing three successful, consecutive commercial-scale events. Results for each
event were compared to the commercial product specifications. The success of this activity
demonstrates that Technology Transfer was both successful and complete.
Figure 18 Recommended summary cover page.
Copyright © 2003 Marcel Dekker, Inc.
protocol. It is also recommended that these approved documents be combined to
yield the report, which should then serve both the planning and communication
purposes. This is shown in Figure 19.
X. CHANGE CONTROL AND SUPAC
Assuming that a validation program has been successfully executed, the focus
should now be on the maintenance of the validated state. A good validation
program requires periodic maintenance and upkeep. Any change to a validated
process likewise requires thorough evaluation and documentation. A typical decision
tree for changes (requiring document preparation) to validated items is
presented in Figure 20. Further, in keeping with the spirit of validation, all
changes to validated processes require a certain measure of control. With a
validated process, one should always have a good indication of what changes
caused what affects. Proper change documentation will enable or permit correlation
between changes made and the resulting process or product impact. Proper
evaluation will often filter out or magnify changes that will prove detrimental
to product quality.
Changes to validated processes/equipment are tracked by validation
change control procedures (or simply change control procedures within some
organizations). One of the tools born out of these procedures is a form for
documenting such changes that highlights the level of validation required and
the validation timing. A general form is illustrated in Figure 21. These forms
typically require completion by the party desiring the change and typically describe
the changes in enough detail so that the evaluating and approving depart-
Figure 19 Validation documents.
Copyright © 2003 Marcel Dekker, Inc.
Figure 20 Validation and validation change control decision tree.
Copyright © 2003 Marcel Dekker, Inc.
Figure 21 Example of validation change control form.
Copyright © 2003 Marcel Dekker, Inc.
ments can render a decision as to whether or not this particular change can be
implemented. It is then circulated to validation and quality assurance, minimally.
Often these forms are circulated to other departments, such as the department
in which the change will occur, and regulatory, for information, evaluation,
and approval. Regulatory involvement is advisable at this stage as changes
affecting processes filed with FDA will require notification.
Reputable manufacturers have been known to notify the FDA of practically
any and all changes of significance to an approved process. In the past,
great difficulty and confusion often resulted within the drug companies due to
the fact that the severity of the changes made was very hard to classify. Additionally,
the appropriate time to notify FDA of changes was always an issue.
The scale-up and postapproval changes (SUPAC) guidelines came into existence
to reduce the difficulty encountered with changes to approved product. These
guidelines, which were developed in the mid-1990s were developed jointly by
FDA and key pharmaceutical industry representatives. They in essence provide
submission guidelines specific to the types of products (immediate release, control
release, solid dosage, transdermal, etc.) under manufacture. They address
the types of changes and the resulting submission timing—immediate notification
versus end of the year reporting.
In actuality, transdermals are very similar to other pharmaceutical products.
Similar to most ethical pharmaceuticals, they have attributes that must
meet specifications at the end of product manufacture. In addition, various
pieces of equipment are used in their manufacture. Changes to these pieces of
equipment can and often do impact these key quality attributes, so what is the
impact of SUPAC on transdermals? Although the guidelines for transdermals
are not yet finalized, it is envisioned that the existing SUPAC guidelines will
prove beneficial to transdermal manufacturers, as potential process changes can
be grouped into various classes and the appropriate reporting actions taken. At
this point, it matters very little that the product type is different. Using the
guidelines will offer a bit more of a challenge, but hopefully the process of
when to notify FDA about changes and the content of the notifications will
become more and more streamlined.
XI. PREAPPROVAL INSPECTION ETIQUETTE
Provided that all transdermal process validations have been successfully completed,
the focus shifts to the preapproval inspection (PAI). A target date for the
PAI is typically known months in advance of the actual FDA visit. It is a good
idea to finalize as many of the supporting protocols as possible during this time.
If a company is fortunate enough to actually execute protocols and complete the
summaries before the PAI, it is recommended that representative copies of the
Copyright © 2003 Marcel Dekker, Inc.
approved validation reports be sent to the officiating FDA office prior to their
actual visit. If the reports are not complete (i.e., summaries not approved), the
possibility of supplying unexecuted protocols should be explored. Again, this
will provide FDA with an opportunity to become familiar with the firm’s documentation,
thereby permitting questions to be formulated in advance. While this
may not seem beneficial to the industry, it may actually serve to decrease the
amount of time that FDA spends in a given facility, potentially lessening the
likelihood of an unwanted discovery.
It is also important that these producing companies understand that any
data and reports submitted to FDA are pictorial representations of the submitting
company. If a company puts together a sloppy submission package with sloppy
development data, sloppy validation data, and so on, then that company should
not be surprised if approval is not granted. Industry must therefore make every
effort to assemble the very best package possible for submission to FDA.
XII. CONCLUSIONS
Companies that fall under the CGMP umbrella must understand what FDA
wants. First, its primary concern is to assure that drugs and devices made by
these companies are fit for consumption. These products must exhibit proper
quality and efficacy (CFR 21), thus the many years of clinical trials entailing in
vitro and/or in vivo challenges, bioavailability determinations, extensive development
data including the generation of stability profiles, the assessment of
impurities in the drug product, the numerous files containing these development
data, and finally, the documentation that the equipment and process have been
acceptably qualified and validated. This is also true of transdermals.
One of the lessons learned is that validation is not cheap; there is no way
industry can gain assurance that a process will always be under control with
just a single event. Validation, by definition, requires multiple events to fully
deliver the confidence that the validated item will perform as expected. Equally
important are the preliminary trials leading up to the validation activity.
Many validation personnel understand the need for and the benefits of
performing trials and stress testing, but do their companies share their understanding?
While many may have a solid understanding, they seldom share the
desire to fund prevalidation trials. This is true because many of these trials
cannot be simulated and therefore performed with actual product.
To summarize, process validation is a requirement imposed by the FDA.
It is referenced in 21 Code of Federal Regulations, Part 210 and 211 [8]. It
is extremely important that each organization have a good understanding and
interpretation of the regulations and do everything it can justify in the pursuit
of process validation. This justification should consider the resources (human,
Copyright © 2003 Marcel Dekker, Inc.
dollar, time) required and of course be weighed against the potential benefits to
be derived from the often strenuous undertaking. It is equally important that the
need for validation be communicated throughout each operating department
within the organization.
Documentation is critical in the validation framework. Simply going
through the motions and not doing a thorough job of documenting may void the
validation effort, no matter how good the execution may have been. If you
cannot produce a document upon request, FDA’s attitude is that the work has
not been done.
Just how do drug and device manufacturers assure that their validations
are compliant with the CGMP regulations? One approach would be that a firm
should first do an adequate job of interpreting the termvalidation. Next it should
logically plan and document its interpretation (in a protocol), along with any
justifications. The next step should be to assure that all equipment and facility
components have been adequately qualified and that those qualifications have
been documented and filed in a retrievable location. This same approach pertains
to process validations. Finally, the recommendations shared in this chapter—
though not for the entire reading audience—may be of use to a majority
of the readers. Using these recommendations should put the manufacturers in a
better regulatory position with respect to their validations.
REFERENCES
1. United States Pharmacopeia (USP). vol. 24. General Discussion/Pharmaceutical
Dosage Forms, p. 2116.
2. RxList Monographs (Transdermals); http://www.rxlist.com/cgi/generic2/estradtd_
cp.htm, p. 3.
3. Brittain, H. G. Validation of analytical methodology. J Val Tech (May 1997).
4. Nash, R. A. Introduction. In: Pharmaceutical Process Validation (1993).
5. Doty, L. A. Statistical Process Control. p. 240 (1991).
6. Neal, C. Technology transfers in the pharmaceutical industry. cGMP Comp (April
1998).
7. Neal, C. Equipment cleaning validations for transdermals. J Val Tech (Nov. 1997).
8. Guideline on the General Principles of Process Validation (May 1987).
Copyright © 2003 Marcel Dekker, Inc.
9
Validation of Lyophilization
Edward H. Trappler
Lyophilization Technology, Inc., Warwick, Pennsylvania, U.S.A.
I. INTRODUCTION
In an ideal world, validation would begin with and parallel product research and
development activities. Validation for lyophilized products occurs more often
during scale-up to manufacturing. Under growing regulatory pressure and the
realization of the greater benefits, however, validation activities are being undertaken
while the product is along the developmental pathway. There are also
circumstances for which validation is required for existing commercial products,
either because of changes requiring additional study, or to meet current regulatory
standards. This presentation will approach validation as an integral part of
developing a new product. Appropriate application of the principles discussed
may be applied for either a change-control procedure or for revalidation, based
on specific needs.
II. ORGANIZING FOR THE VALIDATION
Components of a comprehensive validation program include equipment qualification,
together with product and process validation. Utility, flexibility, and ease
of management are advantages of assembling each validation activity, study, or
test as a distinct, independent entity. The equipment qualification portion focuses
on the equipment and is valid for the processing of any number of products.
Conversely, the process for each product is unique and applies to only one
product. Therefore, process validation id specific for that product.
A validation protocol can effectively be arranged as individual sections.
Organizing the validation project into discrete activities can be advantageous
Copyright © 2003 Marcel Dekker, Inc.
for ease of developing and executing the studies. This is of particular benefit
when validating a sophisticated, complex process such as lyophilization. In this
manner, validation activities are also more manageable. Responsibility for each
individual part is clearly defined and more effectively implemented by individuals
best suited for each part of the validation. For example, a member of the
engineering staff would be more qualified to implement an installation qualification,
rather than validate the process. Just as a research scientist would be best
suited to validate that process, rather than complete an installation qualification.
The validation studies could also be easily scheduled and completed at appropriate
times during either installation of a new lyophilizer or during development
and scale-up of a lyophilized product. Managing a change-control program
as discrete sections is much easier and more effective than in a massive documentation
package.
Development of a new lyophilized product with attention to validation
requirements is easier to integrate into a production environment compared with
undertaking further developmental studies at the time validation is attempted in
manufacturing. For example, in designing the lyophilization process, completing
process studies at the boundaries of a process parameter range would be appropriate
at the time stability studies are prepared. Such an approach results in
greater safety and efficiency in the parameter selection and results in a more
robust process. This notion of establishing a proven acceptable range was first
introduced by Chapman as the proven acceptable range (PAR) approach to process
validation, and is suitably applied to lyophilization [1].
Validation for an existing product requires constructing a development
history profile. This profile should start with preformulation data, span product
and process development, and include commercial product manufacturing. In
reconstructing the development history, the most challenging undertaking is justifying
the product formulation and process design. This is particularly difficult
in circumstances with commercial products that have been developed before the
awareness of the benefits of validation.
When a new product is in the development phase, a comprehensive report
needs to be assembled before scale-up as part of the technology transfer to
manufacturing. This report addresses the starting raw materials, including drug
substance, excipients, and packaging components, along with formulation and
process design. Each facet of the product manufacturing needs to be included,
from formulating procedures through final packaging requirements. In-process
and finished product quality attributes must also be defined. The report needs
to clearly explain the scientific rational and justification for the formulation and
manufacturing procedures.
This development report is a crucial reference for integrating a new product
into a manufacturing operation. Acceptance criteria for any validation study
would be based on product and process requirements outlined in the develop-
Copyright © 2003 Marcel Dekker, Inc.
ment report. The report provides an invaluable reference for change-control program
management and troubleshooting.
Equipment qualification is best considered at the time of equipment specification
and selection. The advantages include more effective project management,
ease of completing the validation package, and speed of bringing the
equipment on-line. Equipment requirements and performance are based on the
needs of the product, as characterized during product development.
As with specifying and purchasing any new piece of equipment, wellwritten
equipment specifications include validation activities for qualifying the
equipment and assuring it meets the requirements for producing the intended
products. Defining testing and documentation needed for factory acceptance
testing (FAT) at the vendor’s facility is also a useful contractual agreement.
A. Sources of Information
Sources for information include research and development (R&D), engineering,
clinical supplies manufacturing, quality control, and regulatory affairs
groups. Technical information such as the physicochemical character of the active
substance and product information, stability data, along with process development
data, and finished product criteria should be available within the development
report generated by the R&D group. Specific information on the
equipment design and performance for the Installation and Operational Qualification
(OQ) portion of a validation protocol should be available from the engineering
department. Other engineering references include maintenance and
calibration procedures. Operating procedures covering product loading and operation
of the lyophilizer may be available within manufacturing documentation.
These would include loading procedures and arrangement of product trays
within the lyophilizer. Finished product-testing methods for the active ingredient,
reconstitution, and residual moisture should be available from the development
scientists, analytical development group, or may already exist as standard
testing methods within quality control. The regulatory affairs staff should be
consulted for commitments made in regulatory filings and communications to
regulatory agencies.
B. Recommendations For a Validation Protocol
The differing circumstances under which a validation study is prompted often
dictate the best approach to be used. Agreeably, prospective validation, for
which the validation studies are all completed and approved before shipment of
any product, is preferred. There are however, opportunities to complete certain
validation studies when producing product intended to be administered to patients.
Such circumstances may arise during clinical manufacturing, when exten-
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sive testing is completed. In such a circumstance, validation is concurrent with
producing these materials. In addition, when implementing validation studies on
an existing marketed product to bring the operation up to current regulatory
expectations, concurrent validation would also be appropriate. Retrospective
validation would be applied to a review of historical data of an existing process
and product. Examples would be the review of the lyophilization processing
data, finished product batch release test data, and stability data from the commercial
stability testing program.
The design of the validation testing and the composition of the protocol
reflect the circumstances under which the study is conducted. For retrospective
validation the “test” may be statistical analysis of batch release data, such as
assay, pH, physical appearance, residual moisture, reconstitution time, and constituted
solution appearance. This retrospective process validation would be intended
to demonstrate that the product is of consistent quality. A critical review
of the processing conditions in a retrospective validation may consist of a “test”
comparing actual processing conditions during lyophilization with ideal parameters.
This not only shows adherence to the defined processing conditions, but
also demonstrates process reproducibility.
Concurrent validation studies may be used during clinical manufacturing
and scale-up activities. Additional testing or an increased number of samples,
as when demonstrating batch uniformity for a large production lyophilizer, may
be conducted as a concurrent validation study. In addition to finished product
testing, short-term accelerated stability may be appropriate before actually releasing
the batch for distribution. Long-term stability studies at the recommended
storage conditions, up to the length of the clinical study or the intended
shelf life of the product would also be appropriate.
Although there are circumstances when retrospective or concurrent validation
may be warranted, prospective validation is certainly preferred. This entails
the testing, review of the data, and approval of the validation package before
releasing product for distribution and use. Identifying the target process parameters
and a proven acceptable parameter range, along with demonstrating consistent
product quality and stability, would be valuable before introducing the product
into a manufacturing environment. It could also decrease the amount of time
that often seems necessary for getting a new product from development through
manufacturing, because alterations during scale-up may be minimized.
Conceptually, there is a logical progression for the various validation studies.
In purchasing a new piece of equipment to produce a lyophilized product,
specifications, verification of the design during the engineering phase, in addition
to simply conducting a factory acceptance testing, would be part of the first
phase of validation. This combination of Design Qualification (DQ) and Factory
Acceptance Tests (FAT) is particularly appropriate for more sophisticated systems,
such as for a large-scale manufacturing equipment. The Installation Quali-
Copyright © 2003 Marcel Dekker, Inc.
fication (IQ) would be implemented during the installation and start-up of the
lyophilizer to assure that the lyophilizer is installed properly and all necessary
support “systems” are in place. These range from basic utility requirements to
standard operating procedures (SOPs). Operational Qualification (OQ) studies,
conducted on successful completion of the IQ, assure that the equipment is
capable of implementing the processing parameters to successfully produce the
product, as defined during development.
For a process validation, all studies may be completed during the development
phase. These studies would correlate the product formulation, presentation,
and lyophilization-processing parameters with finished product attributes. In addition,
the reproducibility of the process would be demonstrated along with the
consistency of finished product attributes. Batch uniformity studies during the
first batches being integrated into manufacturing are often the last leg in the
sequence of validation protocols for bringing a product to market. Depending
on the supporting data available from earlier studies, limited or short-term accelerated
stability may be sufficient.
III. COMPOSING THE VALIDATION PROTOCOL
The design of the validation studies and the format used for the actual protocols
can have a substantial influence on both implementing the protocols and maintaining
a change-control program. Breaking the validation project into small,
discrete tasks makes both managing and implementing the studies easier.
The use of format in which each activity, function, or test is a complete,
stand-alone task and document yields numerous advantages. These advantages
are evident during the writing, reviewing, and implementation activities. Having
discrete documents also allows specific and focused testing that may be appropriate
under a change-control program.
A. Preparation of the Protocol and SOPs
Each activity to be performed as part of the equipment qualification (EQ) and
the entire process for the IQ and OQ can be organized into discrete functions
and documents. For an EQ, whether being simply a FAT or including a DQ for
a more complex system, it is useful to have a stand-alone document that focuses
on equipment design and construction aspects. During the IQ, the reviewing and
verification of utility connections, piping of the refrigeration and heat transfer
system, reconnecting the vacuum system, rewiring of the control system, startup
and testing may be organized into distinct documents for each activity. This
“modular” approach becomes more effective and efficient as the complexity of
the procedures and equipment increases. Each aspect of bring a lyophilizer on-
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line or integrating a new product into a manufacturing environment often involves
several individuals or departments. Correlating distinct activities of the
protocol into small sections makes communication between individuals and departments
more manageable. For example, the project engineer responsible for
installation of a new lyophilizer may use a mechanical contractor to reconnect
the piping and connect the utilities, and use an electrical contractor to connect
the control system wiring. In such a case, a documentation package covering
each activity may be issued and completed for each part of the project involving
each contractor. A documentation package organized in such a manner is also a
useful tool for project management.
Such an approach is also applicable for product and process validation.
Considering the ranges of formulation aspects, such as the acceptable pH range,
a focused study to correlate the pH, phase transition temperature, and finished
product aspects on processing, would be well suited as a distinct protocol. This
specific protocol may parallel studies already conducted during development.
Another example is establishing the proven acceptable range for the processing
parameters. Identifying such ranges is accomplished by processing the product
at extreme shelf temperatures, chamber pressures, and times, following the PAR
approach as described earlier.
Whether during the development of a new process or product, or in designing
an appropriate protocol for a new piece of equipment, organizing the
protocol and identifying the studies to be conducted is the first strategic step.
During product development, there are often many unknowns that exist when
the protocols are written. These can span the testing methods for release of the
drug substance to finished release specifications. The same applies to developing
the qualification protocols for a new piece of equipment at the time the specifications
are written. There may be design changes that will influence the EQ
documentation. In the real world, alterations, ranging from slight refinements,
to major changes frequently occur.
B. Establishing Acceptance Criteria
The selection of acceptance criteria is dependent on the circumstances under
which validation is being undertaken and requires judicious consideration. Challenges
to the equipment, for example, may depend on whether the equipment is
first being installed or whether qualification is being completed for an existing
lyophilizer currently in use. If the equipment is new, the acceptance criteria
based on the performance requirements that are identified within the equipment
specifications would be warranted. The advantage of acceptance criteria based
on stated equipment capabilities is that any process that is within the performance
capabilities of the equipment could be used for processing product. For
testing an existing unit in production, however, the most rigorous processing
conditions would be a justifiable test challenge. The limitation of test challenges,
Copyright © 2003 Marcel Dekker, Inc.
based on the most current processing conditions, although rigorous, is that if a
process for a new product is outside of the parameters tested, then additional
testing or qualification at the new parameters would be necessary.
Details of constructing validation protocols, designing studies, and establishing
acceptance criteria will be presented in each section of this chapter. In
considering the approaches discussed in this presentation, it is important to consider
what would be appropriate and useful in achieving a high level of control
for the project at hand. The validation needs to encompass testing and documenting
of what is critical for gaining a high degree of assurance that the process
is well defined and reproducible, the procedures are adequate and appropriate,
and that the equipment is suitable for completing the process. In addition,
it is a valuable opportunity to collect useful information for implementing a
change-control program. Validating for the sake of simply documenting information
in a protocol, not having a clear understanding of what is necessary, or
creating a voluminous collection of information because more is better should
be avoided. As a general rule, do what is necessary and do it well.
For some studies, as in the OQ, references will be made to common performance
capabilities of equipment. These are intended to be examples, rather
than standards. A few general notes are appropriate. Most importantly, acceptance
criteria needs to be based on a justifiable scientific rationale. This is applicable
whether qualifying an existing piece of equipment for commercial product
manufacture or validating a product and process during clinical manufacturing.
Selecting appropriate processing ranges to be encompassed within the validation
has a major long-term effect in manufacturing. For example, when the range of
residual moisture is adequately determined and correlated with long-term stability
during development, then any batch in manufacturing exhibiting moisture
within the boundaries of that range would be acceptable. If the residual moisture
was beyond the boundary, then there would be concern about adequate stability,
and the batch may not be released. Adoption of such a philosophy provides
clear and reasonable ranges for product manufacture. There is also little question
of what should be done when a batch is outside the proven acceptable range.
This eliminates a scenario of doing additional testing, perhaps even stability
testing, when there is a question of what a suitable envelope of processing conditions
or product quality aspects would be for a manufactured batch. This notion
of establishing a proven acceptable range, or PAR approach, becomes a
valuable asset in a manufacturing environment.
IV. EQUIPMENT QUALIFICATION
Equipment Qualification (EQ) is a useful endeavor when the lyophilizer is a
complex and sophisticated system. Large-scale manufacturing units commonly
include multiple automated support operations. These may include steam-in-
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place (SIP), clean-in-place (CIP), in situ filter integrity testing, and automatedor
robotic-loading systems. The lyophilizer may also be designed for unique
product-processing requirements, as in processing mixed solvents, or unique
dosage forms, such as quick-dissolving tablets. An EQ may include both the
design qualification (DQ) and the factory acceptance testing (FAT). The DQ
encompasses a review of the product and processing requirements and justification
of the equipment design, construction, and performance capabilities. It is
also useful as a structured guide for reviewing the engineering documentation
from the vendor. This includes not only equipment blueprints, but also control
logic and program structure for an automation system. Completing such a review
during the engineering phase of the project provides an excellent opportunity
to verify that the specifications are suitable. The FAT is a series of tests at
the supplier’s factory before shipment of a new lyophilizer. The FAT includes
verification that the equipment’s final design, construction, and performance are
as anticipated when compared with the equipment specifications. This assumes
that the specifications are based upon current or anticipated needs for processing
a product. In the absence of specific processing needs, the reference would be
the specifications agreed to between the vendor and purchaser.
Activities within the FAT are complementary to that of the IQ and OQ
implemented at the final installation site. This would include verification of the
engineering documentation, construction, and assembly of the lyophilizer, along
with demonstration of the equipment performance.
A. Scope and Objectives
For the acquisition of a new lyophilizer, the FAT comprises a series of tests to
ensure that the lyophilizer meets the performance expectations identified within
the purchase specifications and are necessary for its intended use. The intent is
to measure and verify the performance capabilities of the lyophilizer before
shipment to the end user.
B. Early Project Activities
As part of a comprehensive specification package, incorporating the qualification
requirements in the equipment specifications package to the vendor assures
that proper attention is given by both the vendor and purchaser. These validation
requirements include the FATs along with control system validation, and perhaps
even extending to the Installation and Operational Qualification. Identification
of the testing to be done at the factory to complete the FAT protocol allows
sufficient planning for both manpower resources and time at the vendor’s facility.
Validation of the automated system controlling the lyophilization process,
along with the complementary processes, such as SIP and CIP, needs to be
Copyright © 2003 Marcel Dekker, Inc.
started at the control system design and software development stage of the project.
This follows the life cycle [2] approach that has become common industry
practice for validation of computer automation systems.
Part of the FAT that comes before any actual performance testing is the
review and verification of the equipment design. This is sometimes completed
as a separate task and is often referred to as a Design Qualification (DQ). This
step, whether as a separate DQ or as part of the FAT entails a review of the
engineering documentation to verify that the equipment will meet the requirements
of the specification before construction and assembly of the lyophilizer.
Such a review includes the general layout of the equipment, piping arrangements
for the CIP and SIP systems, refrigeration and heat transfer fluid system drawings,
electrical elementary schematics, and P&ID drawings. This review of the
engineering drawings should be documented and become part of the validation
package.
C. Preshipment Testing
Equipment performance tests completed during the FAT involves testing to
demonstrate that the equipment functions and performs as specified. The tests
may mimic those planned as part of the OQ to be conducted at the final installation
site. These tests are useful both in assuring that the equipment is constructed
according to the specifications and also that the performance is adequate. It is
important to acknowledge that utility supplies may affect the equipment performance;
therefore, the acceptance criteria may be different than in the OQ that
will be conducted after the equipment is installed.
Often duplicating the testing for an OQ, test encompass function, control
capability, and performance for freeze-drying and support processes, such as
SIP and CIP processes. The testing regimen should include specific tests as
listed in Table 1. Complementary functions such as sterilization and, if supplied,
Table 1 Equipment Qualification Testing
Shelf heating rate
Shelf cooling rate
Shelf temperature control
Condenser cooling
System evacuation rate
Pressure control
Leak test
Sublimation rate
Condenser capacity
Copyright © 2003 Marcel Dekker, Inc.
cleaning should also be included with equipment having SIP and CIP capabilities.
Testing of the loading and unloading would be appropriate with systems
where an automated-loading system is provided by the lyophilizer manufacturer.
This testing program is useful as part of the validation package, along
with being part of the equipment acceptance. Circumventing the testing at the
vendor’s facility should be avoided, no matter how complex or unique the final
installation. Frequently, correcting a problem or making adjustments to meet
the specifications is easier, less expensive, and faster if completed at the vendors
facility, rather than in the field during installation, or correcting during validation.
In addition, successfully completing the FAT does not negate the need to
complete a comprehensive IQ/OQ at the final installation site. Factors, such as
assembly of the lyophilizer at the final installation site and differences in utility
supplies, warrant testing before bringing the unit on-line for manufacturing product.
The more complex and unique the equipment design and final configuration,
the more such efforts are necessary to assure the success of the project. Some
parts of the IQ could be completed at the factory and not repeated after installation.
Such items may include instrument and hardware documents, testing of the
control system, and verification of as-built drawings, to cite a few examples.
V. INSTALLATION QUALIFICATION
The IQ is often the first validation activity completed when the lyophilizer arrives
at the final installation site. Implementation of the protocol may begin as
the lyophilizer is being installed. For example, verification of the electrical wiring
and piping may be accomplished as part of the assembly activities. The
appropriate approach to completing the IQ is dependent on the specific circumstances
of the project.
A. Scope and Objectives
The Installation Qualification consists of a description of the lyophilization
equipment, a system hardware and component list, the documentation of the
installation procedures, and the equipment start-up and operator training. The
IQ also includes references to the purchase specifications, engineering review,
and SOPs. The objectives are to assure that the equipment design and construction
are appropriate for the intended use, it is installed properly, the utilities are
suitable and adequate, and that procedures are in place for proper maintenance
and operation.
B. Equipment Description
The description of the lyophilization equipment provides a general overview of
the lyophilizer, the installation site, operation, and functions. The description
also identifies the major components of the system. From the listing of the major
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components, a more specific description of each item provides greater detail. Such
information is highlighted in Table 2. This data becomes an integral part of the
change-control system for the equipment hardware. The major components of the
lyophilizer that should be included are the refrigeration units, heat transfer fluid,
heat transfer circulation pumps, heater elements, primary vacuum pumps, secondary
vacuum pumps, system valves, and the control instrumentation.
C. Installation Activities
Documentation of the installation can also be included within the IQ section of
the validation package. Part of this documentation may take the form of an
installation checklist. This checklist would include each specific activity necessary
for the installation of the lyophilizer, who completed and checked the work,
and the date the work was completed. These activities would include assembly
of the various lyophilizer parts (if dismantled at the factory for shipment) and
the connection to utility supplies. In some circumstances, these activities and
the associated documentation may have been completed during the commissioning
of the equipment.
In addition to the early project activities of the engineering review and
factory testing completed as part of the FAT, certain parts of the Installation
Qualification should also be planned well in advance of receiving the equipment.
These include the utility verification, physical installation of the lyophilizer,
start-up, and training. The utility verification, identifying the quantity,
quality, and source of the utilities, is best completed during the initial phase of
the project and before operation of any of the lyophilizer systems. These encompass
electricity, cooling water, process gases, sterilant, and discharges for the
lyophilizer. The listing in Table 3 is of common utility supplies.
Physical installation of the lyophilizer includes the rigging into place and
connection of the subsystems. With large-sized units and those with external
condensers, such connections are fairly involved projects in themselves that in-
Table 2 Hardware Description Data
Manufacturer
Model number
Serial number
Part number
(assigned by lyophilizer vendor)
Utility requirements
Capacities
Reference
(equipment drawings)
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Table 3 Common Utility Supplies
Electric
Voltage, phase cycle, amps
(control circuit power)
Cooling water
Temperature, pressure, flow rate
Compressed air
Presssure, flow rate, quality
Compressed gas (nitrogen)
Pressure, flow rate, quality
clude mechanical, electrical, and refrigeration mechanics. After installation is
complete, most vendors provide a service technician to start up the system and
provide training as part of commissioning the equipment. Such activities need
to be documented and may be included within the IQ portion of the protocol.
VI. OPERATIONAL QUALIFICATION
The Operational Qualification (OQ) focuses on the equipment, rather than the
process. Although not associated with any specific process, the OQ is a series
of tests that measure performance capabilities and demonstrate the ability of the
lyophilizer to complete critical processing steps. Functions of the lyophilizer,
such as cooling and pressure control, are process related. They are, however,
focused on measuring the performance capabilities of the equipment, rather than
demonstrating any processing capabilities relating to producing a particular
product.
A. Scope and Objectives
The OQ demonstrates the equipment performance for the range of processing
functions at the installation site. The tests performed may be expanded to compare
with those completed as part of the FAT at the vendor’s facility. Additional
activities, such as CIP and SIP process development and validation, are also
performed after the IQ has been successfully completed.
1. Measuring Equipment Performance
Although the testing at the factory may have demonstrated the performance
capabilities of the equipment, such tests need to be performed at the final installation
site. Different utility supply capacities, such as cooling water and stream,
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influence the equipment performance. These tests also verify that the utility
supplies are adequate and meet the demands of the operating system. This testing
is particularly valuable for large systems disassembled and shipped as
smaller packages, when the unit is reconstructed at the installation site. Testing
is necessary to demonstrate that installation was completed properly, and that
the equipment still meets the performance levels previously demonstrated.
2. Verification of System Capabilities
The OQ evaluates each equipment function and the capacity to meet the performance
standards. Reducing the lyophilization process into each function also
has advantages for managing a change-control program. For example, one test
would focus on cooling rates used for the freezing step, while a separate test
would be implemented to evaluate the heating function used during primary and
secondary drying. The advantage of having a separate and distinct testing protocol
for each process step is that there is a specific testing protocol for each
discrete equipment function used to complete a step in the process. Constructing
the protocol using such a format later becomes an advantage when a significant
change is made to the shelf-cooling equipment or there is a question about
performance capabilities. A detailed and specific protocol could be implemented
to demonstrate that there is no significant change to the system-operating performance.
Considering each function of the equipment for each step in the process
allows segregation of each equipment function, with a respective test that demonstrates
a specific performance capability.
B. Equipment Performance Tests
Performance capabilities and capacities can be evaluated using a separate test
for each function of the lyophilizer. These tests focus on the operation of selected
subsystems and the capacity for the specific functions during lyophilization.
These subsystems include the heat transfer system, condenser, and vacuum
system. An overview for testing of each major subsystem is presented in the
following sections. Also included are examples and illustrations for performance
ranges. These examples, however, do not, reflect the capabilities of a specific
lyophilizer, nor are they intended to suggest any industry standard.
1. Heat Transfer System
The heat transfer system provides cooling required for freezing the product and
the subsequent heat needed to establish rate of sublimation. Temperature control
is required over the entire process, from the time the product is loaded onto the
lyophilizer shelves until it is removed after stoppering. Therefore, cooling and
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heating rates, along with control at set point, and temperature uniformity, must
be tested.
Maximum cooling and heating rate tests are intended to demonstrate the
optimal performance of the equipment. The cooling rates, defined as an average
of the change in temperature per unit time, are measured from room temperature
to the ultimate achievable freezing temperature. Heating rates are measured from
the lowest to the highest operating temperature for the lyophilizer. For a lyophilizer
currently in use, the acceptance criteria may be the average rate across a
temperature range that exceeds the current process requirements by a few degrees.
Test results are expressed as an average rate of change, as measured at
the shelf inlet. Because the performance of the lyophilizer is strongly dependent
on the specific design, acceptance criteria vary. It is common, however, to be
able to achieve average cooling and heating rates in the range of 0.5°–10°C/
min.
Shelf temperature uniformity across any one shelf and all of the shelves
of the lyophilizer needs to be within an acceptable range to assure batch uniformity
of the dried product. The temperature at any location is compared with
either the mean of the measured values or the temperature indicated on the
controlling instrument. The allowable range is dictated by the reference used,
with tighter tolerances used when comparing the actual with the mean of the
measurements. The stated capability for shelf temperature uniformity by many
of the lyophilizer vendors is ±1°C at steady-state conditions. Appropriately completed
under no-load conditions, these functions may again be demonstrated
under load conditions during the sublimation–condensation test.
2. Condenser
Measuring the cooling rate and ultimate lowest temperature of the condenser is
useful in generating baseline data for future reference, such as monitoring the
condition of the refrigeration system. As with the shelf cooling, the rates will
vary based on the size, type and number of refrigeration units on the system.
The ultimate condenser temperature necessary is dependent on the solvent system
used to solubilize the material to be dried. For a completely aqueous solvent
system, a maximum allowable temperature is commonly ?50°C. For processing
some organic solvents, the necessary condenser temperature is dependent on the
solvent being processed. For example, ethanol vapors must be chilled to below
?115°C before condensation and solidification will occur, whereas tertiary butyl
alcohol requires to be only slightly colder than room temperature.
In the sublimation-condensation test, the condensation rate, and ice load
capacity are demonstrated. In these tests, the actual performance is more critical
than the baseline test of cooling rate and ultimate temperature. The rate of condensation,
expressed as kilograms of ice per hour, becomes a limit to the pro-
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cessing parameters that may be used in design of the lyophilization cycle. The
results of the ice capacity test become a limit to the product batch size.
3. Vacuum System
Similar to the cooling rate and ultimate temperature tests for the condenser,
evacuation rates and lowest achievable pressure are baseline tests that indicate
the performance of the vacuum-pumping system. Typical evacuation rates permit
reaching 10µm Hg within 20–30 min. The lowest achievable pressure is
commonly 20µm Hg or less.
Associated tests to include are leak rate and vacuum integrity tests. Both
tests are based on the pressure rise of a sealed chamber and condenser that are
isolated from the vacuum pumping system. A detailed presentation on the subject
is covered in various technical publications on vacuum technology [3,4].
Each of these tests, briefly described in the following paragraphs, is well suited
to be stand-alone protocols.
The leak rate test is a baseline measurement that is intended to determine
the presence of leaks in the freeze-dryer chamber and condenser. The test is
implemented with the chambers being clean and dry, and with low levels of
outgasing. Eliminating any vapors that may outgas and contribute to a pressure
rise requires that the test should be done only after the system has been maintained
at a low pressure for several hours. Acceptance criteria often used are the
specifications agreed to by the equipment vendor and end user. The values for
this test most often quoted by equipment vendors is 6 ? 10?4 Pa-L/min (6 ? 10?4
Pa-L min?1), equivalent to 4.5 ? 10?6 mmHg-L/min (4.5 ? 10?6 mmHg-L min?1)
for a completely assembled system. These values, however, are arbitrary and
have little technical significance other than illustrating the relative tightness of
the lyophilizer at the time the test is conducted. The standard may be expressed
as units of pressure per unit time for a system of given volume or units of
pressure and volume per unit time that would apply to any size system.
The vacuum integrity test is an in-process method used in manufacturing
after the completion of sterilization and before loading product. Results of this
test compare with a different standard than the baseline leak test because there
is significant outgasing present from prior sterilization. Because every system
and sterilization procedure may be different, a study to establish an acceptable
value that accommodates outgasing of water vapor is necessary. Justifying an
acceptable number is accomplished by correlating a rate of pressure rise that
includes any contribution of outgasing of vapors from residuals left over after
the sterilization process. Therefore, this requires that a test study is conducted
after the sterilization process has been validated, because sterilization conditions
may influence the amount of outgasing that occurs. Results of this study yield
a value expressed as a pressure increase per unit time, such as Pascal, millime-
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ters, or microns per minute. Although there have been discussions on the topic
published, there is no industry standard established that is based on either empirical
data or a justifiable scientific rationale [5,6].
C. Control Functions
Whether a control system comprises distinct instruments for nominal control
functions and process monitoring, or an integrated control system, a nominal
set of control function tests are necessary. The tests described encompass both
controller capability and equipment performance. These tests may be completed
during the FAT as part of a separate computer system validation.
1. Shelf Temperature Control
Different from the achievable heating and cooling rate capabilities, shelf temperature
control tests combine the system capabilities in implementing a range of
cooling and heating rates and control at a specific set point across the operating
range of the system.
For cooling and heating, minimum and maximum rates are challenged.
These rates may be based on either anticipated processing conditions or the
vendor’s stated equipment performance over the operating range of the system.
Rates for both cooling and warming may range from a minimum of 0.1°C/min
to maximum of 1.0°C/min.
Shelf temperature control tests demonstrate the system’s ability to maintain
steadystate shelf temperature used for the freezing and drying process and
should be within an acceptable range near a target set-point. If the acceptance
criterion is other than the vendor’s stated operating range, then control points
used for the test must envelop the temperature ranges to be used for processing.
Equipment capabilities range form ±1° to ±5°C from the target set point, as
measured at the control point. Typical manufacturing units range within ±3°C.
2. Pressure Control
The pressure control capability, critical as a process parameter, needs to demonstrate
the accuracy and precision of pressure control across the range anticipated
for the lyophilization cycles. This range can be a pressure as low as 20µm Hg
(0.026 mbar) or as high as 1600 µm Hg (2.08 mbar). The results of the test are
compared with the target values at low, intermediate, and high pressures. Acceptance
criterion is stated as an acceptable range near the three target set points. An
acceptance criterion of ±10 µm Hg (±0.013 mbar) is readily achievable.
3. Process Monitoring
Defining the process as critical parameters of shelf temperature, chamber pressure,
and time dictates that monitoring these conditions is performed with suitable
accuracy and precision. Product temperatures, being less critical because of
Copyright © 2003 Marcel Dekker, Inc.
intrinsic limitations, are also commonly monitored. The ability of the monitoring
system to reflect the actual process status is assured by an appropriate calibration
program. It is appropriate to complete a comparison of values measured if
multiple instruments are used for monitoring the same conditions or if data is
transferred from a recording instrument or PLC to a computer workstation. This
activity is normally conducted as part of the control system validation and needs
to be completed before starting the OQ testing, because those instruments will
be used for control and data collection.
4. Sequencing Functions
With an automated control system, verifying the sequencing functions may be
appropriate during the OQ testing. The first step is verifying the interfaces to
the field devices, such as pumps, motors, and valves, and their proper operation.
This should include operation of proportional control valves.
This verification may have been completed separately as part of the control
system qualification and, therefore, would not be necessary during the OQ
studies. In verifying the control sequence functions, the hardware engaged for
each step and the successful progression through the process, are compared with
that identified from the control system flowchart. Whether completed during the
OQ, or separately during control system validation, is of little importance. However,
it is preferred that the control system be qualified before implementing
any of the OQ testing, especially any integrated control functions, such as the
lyophilization process tests. As noted in the introduction, computer control system
validation has unique requirements for validation and would best be accomplished
as a separate study. The PDA Technical Report No. 18, Validation of
Computer-Related Systems, provides a useful reference for control system validation
[2].
5. Integrated Process Control Functions
Integrated control functions encompass the lyophilization process itself, along
with alarm functions and fail-safe responses to out-of-range process conditions.
Critical parameters of shelf temperature, chamber pressure, and time, and the
success in controlling these parameters within an acceptable range, are demonstrated
during the actual lyophilization of material. For ease in completing the
testing and as a precursor to implementing a process with test material, the
lyophilization cycle may be run using an empty chamber with alarm function
tests and fail-safe responses challenged. During this “dry run” the logical responses
of the control system, along with the behavior of the physical equipment
components, are demonstrated. Response to alarm conditions, such as the shelf
temperature and chamber pressure, may be altered by physically forcing such
conditions. For example, directly engaging the heaters would cause the shelf
temperature to warm above the allowable target set point range. Engaging the
Copyright © 2003 Marcel Dekker, Inc.
refrigeration compressor when the shelves are at the target set point would cause
the shelf temperature to fall below the range, also instituting an alarm condition.
Fail-safe responses wold also be tested in a similar manner. Table 4 highlights
some of the critical parameters that wold be appropriate to test during such a
simulation.
D. Process Testing
The basic functions are demonstrated and performances measured in the collection
of tests described in the preceding sections. The principle elements of the
system functions are complete; the next step is to demonstrate that the discrete
functions can be combined as an integrated process. Process testing combines
functions tested separately in the preceding steps of the OQ studies using a
model product. Such a study challenges the integrated control capabilities, orchestrating
the functions and capabilities of each component of the system to
implement actual processing parameters for a complete lyophilization cycle.
This combines the equipment performance and control capabilities, implementing
variable processing conditions that encompass the dynamics of the process.
In concept, the test bridges functions of the individual system components and
the control instrumentation to the system successfully manipulating the environmental
conditions to within reasonable processing parameters. This testing also
provides an opportunity to demonstrate batch uniformity capabilities. It is important
to note that this process testing is independent of any particular processing
parameters and any specific product presentation. Rather, it is a series of
tests designed to demonstrate the capability of the equipment to reproducibly
implement the lyophilization process and yield consistent product qualities, independent
of the location of the product within the lyophilizer. Identification
of suitable locations for product monitoring and sampling during performance
qualification studies that are product specific may be derived from these studies.
1. Product Uniformity
As in any pharmaceutical batch operation, batch uniformity is paramount. Studies
by Greiff [7] have shown that when lyophilizing a 3-ml volume of a 2%
serum albumin solution in a 10-ml–tubing vial there is a measurable effect of
Table 4 Process Fail-Safe and Alarm Tests
High shelf temperature
Low shelf temperature
High chamber pressure
Low chamber pressure
Copyright © 2003 Marcel Dekker, Inc.
location within the lyophilizer on the amount of ice sublimed and the residual
moisture. His studies also quantified the patterns of distribution for vials with
low, intermediate, and high residual moistures varied with the shelf temperature,
the shelf position, and elapsed processing time. In this specific example, the
effect of processing conditions, time, location of the vial on the lyophilizer
shelf, and the influence of heat transfer through a clear Plexiglass door, are well
demonstrated. This study illustrates how such factors as location of the product
on the shelf warrants demonstrating that such influences can be controlled
within acceptable levels.
Mapping of the chamber is an effective method of quantifying any effects
of location and surrounding environmental influences, such as differences in
heat transfer. The result of such a study can be used to identify appropriate
locations for monitoring and product sampling during actual product validation
studies, as well as to demonstrate sufficient batch uniformity.
These trial runs also verify adequate process parameter control of shelf
temperature and chamber pressure under load conditions. The batch size and
process parameters do not necessarily need to duplicate those for any actual
product. Rather, it provides the opportunity to design an appropriate model to
challenge the equipment capabilities. Several models have been proposed, ranging
from a placebo of a specific product formulation to a combination of mannitol
and arginine, in vial sizes from 10 ml to 100 ml [8].
Lyophilizing multiple batches of a model product provide a challenge to
demonstrate the equipment’s performance capabilities under load conditions.
Process parameters of shelf temperature, chamber pressure, and time are compared
with target values. In addition, product response in the areas expected to
impart the greatest variation, such as the perimeter of the shelf, can also be
assessed. The range of product temperatures and the distribution of times when
monitored vials achieve the end point of drying can also be compared. Variation
in the time when there are sudden increases in product temperature, referred to
as a “break” in the product temperature, can also be influenced by the vial type
and location of the thermocouple placement [9]. This can be effected by differences
in mass transfer of the water vapor through the dried product [10]. Figure
1 illustrates the variation in product temperature for a formulation containing
protein, mannitol, and glycine at various concentrations. Therefore, the significance
placed on any variation in product temperature and time the temperature
breaks along with conclusions drawn from such data, needs to account for such
inherent influences.
Finished product attributes, such as physical appearance, reconstitution
times, and residual moisture, are more effective in quantifying the magnitude of
any variation owing to product location inside the lyophilizer. Differences in
vial content of the active ingredient, assuming that filling of the vials started as
a true solution that is inherently homogeneous, would not be affected by loca-
Copyright © 2003 Marcel Dekker, Inc.
Figure 1 Temperature variation during drying for a 2-ml–tubing vial with combinations
of a protein-mannitol-glycine formulation.
tion. Any differences in purity, presence of degradation products, and changes
to the active ingredient content from the beginning to the end of the filling
operation would be monitored during the initial scale-up batches. Any differences
can also be monitored as a matter of routine by sampling the first and last
vials placed in the lyophilizer.
An advantage in utilizing a model formulation is that excipients that are
not significantly influenced by rate of freezing may be selected, but will indicate
subtle differences in measurable in-process characteristics, such as temperature,
and attributes of dried product, such as residual moisture. The excipient, concentration,
and fill volume all influence the variation in physical structure and density
and, therefore, affect the rate of mass transfer of water vapor during sublimation
[11]. For example, dilute solutions of excipients, such as mannitol,
polyvinylpyrrolidone and simple ionic salts in the range of 5–12% w/v, solidify
with a dense, uniform structure, regardless of the rate at which the material is
cooled during freezing. Significant differences in structure can be observed with
excipients, such as dextran, sucrose, and lactose, when solidified at different
rates of cooling during freezing [12]. These differences may be improperly interpreted,
thereby providing false indications of any variation caused by position
Copyright © 2003 Marcel Dekker, Inc.
because of variations in both product temperature and residual moisture. These
materials, therefore, should be avoided.
VII. LYOPHILIZATION PRODUCT QUALIFICATION AND
PROCESS VALIDATION
Lyophilization is a method of preservation in which the conditions necessary
for the process are dependent on the characteristics of the starting material. The
finished material is dependent on the processing conditions used for freezing
and freeze-drying. This requires that the physiochemcial character of the material
be well defined and understood to develop a suitable process. For routine
processing, the consistency of the starting material may dictate the level of
success during processing. Such data is a prerequisite to designing an appropriate
process. There may also be characteristics of the material that allow quantifying
the level of success of processing. As an example, x-ray diffraction may
be used for a material that may crystallize under certain processing conditions.
Therefore, the morphology may be monitored to assess the level of success in
achieving the desired processing conditions and resulting product characteristics.
In addition, the quality and adequate characterization of the starting material
must be considered when undertaking a validation study, and are discussed
within the following sections.
Definitions for validation published in the Federal Register in May, 1996
emphasize the distinctions between process and validation [13]. Process suitability
is described as “ . . . established capacity of the manufacturing process to
produce effective and reproducible results consistently.” Process validation is
defined as “ . . . establishing, through documented evidence, a high degree of
assurance that a specific process will consistently produce a product that meets
its predetermined specifications and quality characteristics.” Section 211.220,
describing process validation again, includes demonstrating reproducibility of
the process as a requirement.
The application of lyophilization is employed for the preservation of materials
that are normally chemically unstable in solution. Demonstrating that a
process produces product of suitable quality characteristics implies that such
minimum product quality level is inherent at the time of release and throughout
the shelf life of the product. Preservation of quality characteristics is then an
inherent result of the process as well as a requirement of the product. This places
a greater emphasis on correlating product stability to processing conditions. This
emphasis is carried through the portion of this chapter relating to process development.
Applying these validation concepts to lyophilized processes and products,
the significance of development activities and the suitability of validation
during development becomes apparent.
Copyright © 2003 Marcel Dekker, Inc.
A. Preformulation Data
As part of the preformulation activities, investigations include physiochemical
character, purity, solubility, stability, and optimal pH studies. In preparation for
clinical studies, potential product formulations considering route of administration
and solution stability are also studied. Unique to dosage form development studies
for lyophilized products, thermal analysis of the drug substance and product formulations
are also necessary. Data generated during this phase of product development
is useful for future development activities, along with validation.
For lyophilized drug products, the active substance purity and morphology,
formulation procedures, excipients used, and initial concentration may affect
behavior during processing and dried material stability, with a wide variety
of examples in the literature. For example, certain ?-lactam antibiotics may
solidify to an amorphous or crystalline morphology. Each different form exhibits
different physiochemcial properties, such as solubility and stability [14]. In
addition, pH may be an influencing factor in the phase transition of the substance
[15]. The presence of certain excipients may also alter the morphology
of the active substance [16]. Degradation pathways involving hydrolysis, common
for products that require lyophilization, are also significant. For biopharmaceuticals,
numerous biochemical reactions such as hydrolysis, oxidation, deamidation,
?-elimination, and racemization play an important role in the stability of
the final product [17]. It has also been reported that residual levels of an impurity
in mannitol as low as 0.1% w/w was responsible for the degradation of a
polypeptide during storage [18]. There are often a significant number of critical
characteristics that need to be considered in the manufacturing of lyophilized
products. These include the inherent variability in quality and purity of the active
ingredient and product formulation along with the robustness of processing
methods developed and subsequently validated.
Development studies, summarized within a distinct report on the physiochemical
aspects, drug substance attributes, and finished product characteristics,
become critical parts of the validation package. Such data is also valuable for
future integration into a manufacturing operation. This includes the scientific
rationale for formulating and bulk-handling procedures, lyophilization processing
parameters, finished product analysis, and stability requirements.
B. Development Activities
Development activities encompass drug substance characterization, formulation
design, packaging selection, and process development for manufacturing. Each
of these aspects influence the lyophilization process. For a drug substance, upstream
processing and quality aspects of the starting material need to be quantified.
These quality aspects include both assay and purity. In particular, levels of
Copyright © 2003 Marcel Dekker, Inc.
residual solvents, intermediates, as well as degradation products are of interest.
In development of drug products, formulation design, and procedures, a suitable
container and closure, and the lyophilization process need to be studied during
product development. Stability of the bulk solution and constituted product,
along with stability in the dried state, and effects on processing all need to be
considered in the formulation design. Once the quality of the drug substance,
optimal formulation, and product presentation have been identified, design of
the lyophilization process can be completed.
Acknowledging that validation is an intimate part of development, considerations
for each major phase of the development activities will be reviewed.
This review starts with studies of the drug substance and progresses through
finished product testing.
1. Drug Substance
The physicochemical character of the active ingredient directs the formulation
design and selection of excipients for the finished product. If, for example, the
drug substance has a propensity to form either an amorphous or crystalline
phase, the method of freezing and the character of the material need to be assessed
during development. From a theoretical basis, a crystalline form is more
thermodynamically stable than a material solidified during freezing in the amorphous
form. For example, the solid-state decomposition of cefoxitin sodium can
occur at different rates. The amorphous form yields a 50% loss of the active
ingredient within 1 week at accelerated storage conditions of 60°C. The crystalline
form exhibits less than a 10% loss in 8 weeks under the same conditions
[19]. Investigating the physicochemical character of the active material, therefore,
needs to be studied during development. In such circumstances where there
may be different morphological forms of the active ingredient or excipients used
in the formulation, the influence of processing conditions is critical, as discussed
later in this chapter.
The specific physicochemical character of the material may be a useful
means for verifying reproducibility during the validation studies. Materials that
will form a crystalline structure and have good bioavailability and stability may
be formulated with mannitol as an excipient, where both the active compound
and mannitol readily crystallize. However, some substances will alter the morphology
of other excipients or the drug substance. These differences may be
quantified with analysis by x-ray diffraction. Peptides and globular proteins tend
to inhibit the crystallization of some excipients that would otherwise crystallize.
An example of this is the affect of human growth hormone (hGH) on the morphology
of glycine and mannitol [20]. In such circumstances, monitoring the
physicochemical characteristics of the substance can be useful in qualifying the
formulation design of the finished product. It may also be a useful tool in assessing
process reproducibility and product consistency.
Copyright © 2003 Marcel Dekker, Inc.
Another factor that needs to be considered is the purity profile of the
active substance. For example, a synthesized drug substance precipitated out of
an organic solvent may contain trace amounts of the crystallizing solvent. Even
minute levels of residual solvent or other impurities can affect the measured
phase transition of the material [21]. Therefore, the amount of allowable trace
solvents or impurities and their effect on product behavior during processing
need to be evaluated in early development studies. This may also be appropriate
as a monitoring concern during validation.
For biological preparations, upstream purification of peptides and proteins
may use combinations of organic solvents and acids to elute the substance from
the chromatography column. A peptide may orient itself in either an ?-helical
or ?-pleated sheet configuration, depending on the presence and concentration
of an organic solvent. As a consequence, the behavior in solution or during the
freezing process may differ substantially for each conformation. Trace amounts
of solvents and acids may also affect the behavior of the substance in solution
and during freezing. Such details of the requirements, sensitivities, and behavior
of the active substance need to be defined in the scheme of development and
evaluated during validation activities. An appropriate purity profile should be
established and monitored to provide control over the starting raw material.
Specification for residual substances, including processing solvents, chemical
intermediates, precursor fragments, along with microbiological quality are also
necessary. Acceptable levels of degradation products from upstream processing
and bulk solution stability also need to be established during development and
may be used during scale-up and full-scale validation studies to demonstrate an
adequate level of control during processing.
When given the active substance characteristics determined during development
acceptance criteria for the validation studies can be established. These
criteria will demonstrate the consistency of the dried material processed within
a proven acceptable range in the development phase and adequacy of the scaleup
to manufacturing. To be comprehensive in this presentation, numerous aspects,
although not necessarily applicable to all products, are presented as illustrations
in the following sections.
In circumstances during which the active ingredient or any excipient may
crystallize, monitoring of the morphology in evaluating the dried product may
be warranted. If differences in solubility, reconstitution rate, or stability are
imparted by the morphology, then a quantitative method should be included for
assessing finished product attributes. Methods of analysis for dry powder include
infrared spectroscopy, nuclear magnetic resonance, particle morphology,
thermal analysis, and x-ray diffraction [22].
Degradation products that may form through hydrolysis, oxidation, or specific
biochemical reactions should be monitored by an appropriate analytical
method. Polymerization, aggregation, and denaturation levels may be included
in the finished product and stability-monitoring protocols if warranted.
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2. Finished Product Formulation
The solubility and stability based on pH are important in identifying the acceptable
pH range for the product formulation. In some instances there is a compromise
between solubility and stability, either for the bulk solution or dried product.
For example, a 1 pH unit shift from pH 5 to pH 4 for penicillin increases
the solubility along with opportunistic degradation reactions by 1 log [23].
The effect of bulking agents and their interactions should be studied and
understood during development. Along with measuring the degree of crystallization,
this may provide a quantitative measurement that may be useful for demonstrating
process reproducibility and product consistency. Formulations containing
excipients that tend to crystallize, such as mannitol or glycine, may be more
useful.
The effects of the variations in pH or the influence of any buffering system
also needs to be studied. Any influence on the behavior of the active ingredient
or excipients during the freezing and the phase transition on warming
should be considered. As an example, in a biopharmaceutical formulation containing
glycine, adjusting the pH with sodium hydroxide forms sodium glycinate.
The behavior of sodium glycinate in the formulation may be different from
that expected of glycine in the free acid form. Such differences in physicochemical
nature and phase transition temperature have been evaluated [24].
Unless there is a specific and critical function of an excipient, an assay is
not normally considered to be necessary during validation. There are, however,
formulations for which an excipient is critical to the function of the active ingredient.
For example, for some in vivo imaging agents, the reduction of stannous
chloride is necessary in the coupling of a radiolabeled compound. For amphotericin
B, deoxycholate sodium is used as a solubilizing agent and needs to be
at a minimum concentration to assure that the drug is completely soluble on
reconstitution. The concentration of the excipient in these two examples is critical
and an assay would be appropriate.
3. Determining Thermal Characteristics
To establish the shelf temperature necessary to completely solidify the product
during freezing, the required temperature necessary to achieve complete solidification
is determined by thermal analysis early in product development. In addition,
if the formulation undergoes crystallization, such behavior during freezing
and the optimal processing parameters used for cooling the product are critical
and need to be well defined.
With low-temperature thermal analysis, the phase transitions during cooling
and warming are critical data necessary to justify the scientific rationale for
the process and identify appropriate processing levels. This is not only necessary
for determining the ultimate temperature for cooling the product during freezing,
but also for determining the maximum safe threshold temperature during pri-
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mary drying. In certain instances, the temperature during primary drying is critical
for the product in the presence of ice and early in secondary drying. For
example, the solid-liquid phase diagram for sucrose, presented by MacKenzie,
indicates that there is a glass transition at ?32° to ?34°C when the sucrose is in
the presence of ice and before any significant desorption [25].
Commonly used methods for low-temperature thermal analysis needed for
lyophilized products are highlighted in Table 5. Each of the methods available
for low-temperature thermal analysis has particular advantages. Although the
nature of the material sometimes dictates the most applicable method, confirming
analysis by a second method is a valuable tool in fully understanding the
behavior of the material under freezing and freeze-drying conditions. Differences
in measurements and observations and the effect on the drying conditions
designed for processing warrant the use of confirming methods.
4. Assessing Bulk Solution Stability
Assay methods for monitoring any degradation products may be used to justify
the time limits for bulk storage. This time would include the period from when
the product is formulated to the end of the filling operation. Because most lyophilized
formulations do not contain a biological preservative, microbiological
quality before sterilization by filtration must also be monitored. The unfiltered
solution bioburden would include microorganisms and endotoxin levels.
Besides monitoring bulk solution qualities by conventional analytical
methods, measurement of the phase transition may also be warranted. Slight
differences in the nature of the formulation owing to aging, undetected by typical
analytical methods, may influence the phase transition of the product formulation.
For example, absorption of carbon dioxide from the air over an extended
time period may cause a pH shift, consume one component of a buffering system,
or promote degradation. For a peptide or protein with both a hydrophilic
and hydrophobic nature, alterations to desired secondary, tertiary, or quaternary
Table 5 Methods of Low Temperature Thermal Analysis
Method Principle Indication
Differential scanning calorimetry Change in molecular heat Glass transition and eutectic melt
(DSC) capacity
Electrical resistance (ER) Change in electrical Glass transition or eutectic melt
conductivity
Freeze-drying microscope Direct microscopic obser- Fluid flow and structural collapse
vation
Copyright © 2003 Marcel Dekker, Inc.
structure may develop. As a result, polymerization, aggregation, or denaturation
may occur. Any one of these may change the phase transition and alter the
solidification temperature or finished product characteristics. If such an opportunity
exists, then the conformational changes need to be monitored to justify and
validate the allowable bulk storage conditions, such as temperature or atmospheric
conditions, including a suitable time.
5. Justification of Processing Parameters
During the process development phase, ideal processing conditions should be
devised as target parameters to yield desired finished product qualities and acceptable
stability. Those target processing parameters (shelf temperature, chamber
pressure, and time) that are safe, effective, and efficient are selected and
studied during the development phase. A temperature for completely solidifying
the product during freezing is established based on results of thermal analysis
studies.
Thermal analysis data also dictate the maximum product temperature allowable
during primary drying. Shelf temperatures and chamber pressures are
then selected to assure that the product remains below this critical threshold
temperature during primary drying. Secondary drying conditions necessary to
achieve the desired residual moisture content are also identified. Determination
of these processing parameters requires numerous process studies and corresponding
stability studies to define optimal conditions.
The result of such process development studies would be a definition of
target-processing parameters for shelf temperature, chamber pressure, and time.
These parameters encompass the time from when the product is loaded onto the
shelves of the lyophilizer until the product is stoppered and removed. In addition,
the rates of change from one shelf temperature to another also need to be
defined. These rates of change, referred to as ramps, include cooling rates during
freezing, warming of the shelf at the beginning of primary drying, and the transition
from primary to secondary drying.
As an example, the complete process description for methylphenidate hydrochloride,
a product containing mannitol in which the active ingredient has a
phase transition of ?11.7°C, may be described as outlined in Table 6 [26]. Material
processed according to the predetermined conditions would be expected to
yield product of acceptable quality, purity, efficacy, and stability. Reproducibility
of these parameters is demonstrated by comparing the actual processing parameters
for any one batch with the ideal target parameters identified as a result
of development studies. Evaluation of the finished product qualities and assessment
of the stability over the desired shelf life demonstrate that the processing
conditions are suitable and appropriate. Implementing the same process conditions
and achieving the same finished product qualities and stability confirms
that the process is reproducible and the product qualities are consistent.
Copyright © 2003 Marcel Dekker, Inc.
Table 6 Definition of Target Process Parameters
Process step Shelf temperature (°C) Rate (°C/hr) Chamber pressure Time (hr)
Product loading 5° Atmosphere 2
Cooling rate 0.5
Freezing ?20° Atmosphere 4
Ramp to primary
drying 0.5 80 µm Hga
Primary drying 65° 80 µm Hg
Ramp to secondary
drying 0.5 80 µm Hg
Secondary drying 40° 80 µm Hg 8
aThe pressure reported ranged from 210 to 15 µm Hg; 80 µm Hg was selected as a reasonable level
for discussion.
It is also appropriate that the range of processing conditions deemed to be
acceptable produce product of adequate quality and sufficient stability. These
include a range for the shelf temperature during freezing and drying, the chamber
pressure for drying, and time at secondary drying conditions. Selection of
the suitable ranges for the processing conditions must be based on empirical
data from developmental studies or capabilities in a manufacturing environment,
rather than simple arbitrary selection.
Following an experimental design approach for developing a matrix of
variables is undoubtedly a preferable method for conducting experimental studies.
This type of an approach to process validation may be suitable for experimental
design, but becomes extremely cumbersome when reproducibility of the
process and consistent product quality is to be demonstrated. In the absence of
the many studies required to fulfill a complex matrix, a simpler matrix based
on the edges of a defined range would be reasonable and scientifically valid.
Process conditions that affect both the product temperature and rate of
drying are shelf temperature and chamber pressure. For these process conditions,
target parameters, along with suitable ranges above and below the target parameters,
need to be studied and defined during development. Therefore, validating
the process requires demonstrating that if conditions existed during which the
process was completed at the extremes of the range for these conditions, the
finished product would have the same qualities as if the batch were processed
at the target parameters. Because both the shelf temperature and chamber pressure
are independent parameters, the various combinations of both conditions at
the extremes and at the target would establish a PAR [1]. The goal of the process
validation studies for a PAR is to verify that if the process was completed within
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any combination of the two variables, then the finished material would be of
consistent quality and stability.
The design of a series of studies based on the variables of shelf temperature
and chamber pressure would encompass, minimally, permutations of high
and low conditions for each. Demonstration of reproducibility is also an objective
during validation, such that three batches processed at the target conditions
would also be necessary. This, therefore, would require a minimum of seven
batches: three at the target parameters to demonstrate reproducibility and four
for the combinations of high and low conditions.
In addition to the shelf temperature and chamber pressure, the time to
complete secondary drying will influence the residual moisture content of the
dried material. If we assume that a target residual moisture content is known,
the validation studies should also encompass a range of time at the secondary
drying conditions necessary to achieve the desired residual moisture. The range
of time could be incorporated within the three batches at the target shelf temperature
and chamber pressure. As an illustration, and using the cycle defined for
methylphenidate described in Table 6, the variations in shelf temperature, chamber
pressure, and time in secondary drying are presented in Table 7.
The parameters outlined in Table 7, consisting of high shelf temperature
and high chamber pressure would provide the upper level of processing conditions.
During freezing, the shelf would be controlled at the maximum or warmest
temperature at which solidification would occur. During primary drying, the
warmest shelf temperature and highest chamber pressure would result in the
greatest amount of heat supplied to the product. This increased amount of heat
Table 7 Varied Process Parameters for a Proven Acceptable Range
Ramp to Ramp to
Product Cooling primary Primary secondary
Process condition loading rate Freezing drying drying drying Secondary drying
Shelf temperature
High 10°C 0.5°C/hr ?15°C 0.5°C/hr 60°C 0.5°C/hr 35°C
Target 5°C 0.5°C/hr ?20°C 0.5°C/hr 65°C 0.5 °C/hr 40°C
Low 0°C 0.5°C/hr ?25°C 0.5°C/hr 70°C 0.5°C/hr 45°C
Chamber pressure
High 100 µm 100 µm 100 µm 100 µm
Target Atmo- Atmo- Atmo- 80 µm 80µm 80µm 80 µm
spere sphere sphere
Low 60 µm 60µm 60µm 60 µm
Time 2 hr 2.5 hr 7 hr 6 hr 8 hr 10hr
Copyright © 2003 Marcel Dekker, Inc.
would be expected to result in a greater rate of sublimation, warmest product
temperature, and possibly the shortest processing time. In considering the effect
during secondary drying, the high levels would provide potentially higher rates
of desorption and, therefore, the lowest residual moisture content. The end result
should be the slowest freezing rate, fastest drying rate, warmest product temperature
during the process, and lowest residual moisture.
The matrix of varied processing conditions outlined in Table 7 encompasses
the coldest shelf temperature and highest chamber pressure. In this study,
a decrease in the rate of sublimation, compared with the foregoing cycle conditions
is anticipated because the shelf temperature is lower and a resulting decrease
in the amount of heat energy to support sublimation would occur. However,
there would be a contribution in heat transfer by the increased chamber
pressure, compared with the target-processing conditions. Although the rate of
sublimation and desorption would be lower than that of the first study, they may
be greater than those expected for the target parameters.
A higher chamber pressure would provide greater efficiency in heat transfer
from the shelf. Any increase in the overall amount of heat transfer relative
to the parameters outlined in Table 7 would depend on the specific parameters
selected. The greatest anticipated effect would be on the product temperature
owing to the increase in chamber pressure. This effect would be strongly dependent
on the specific processing pressure. For example, the effect of a 20-µm
increase is greater at a target pressure of 80 µm than it would be at a target
pressure of 400 µm. For these sets of processing conditions, product temperatures
during each process phase, rates of drying, and residual moisture content
would be intermediate compared with the other studies.
As compared with a higher pressure and lower shelf temperature outlined
in Table 7, drying rates with the reversed conditions of lower pressure and
higher shelf temperature would be expected to be slower than the conditions at
target shelf temperature and chamber pressure. Compared with those conditions,
freezing would be expected to require more time. Primary drying rates would
also be reduced because heat transfer rates would be less, product temperatures
lower, and residual moisture higher.
The longest times for the product to reach completion for each cycle phase
would result from the combination of a lower shelf temperature and chamber
pressure. In this study, the principal objective is to demonstrate adequate times
allocated for each portion of the process, even under the conditions where the
heat transfer was low and times were longest compared with the target parameters.
Here the heat transfer would be lowest and, therefore, the freezing and
drying require the longest time. The product temperature would also be expected
to be the lowest compared with the other processing conditions. Processing under
these conditions of the least heat supplied to the product demonstrates that
there is sufficient time designed within the cycle parameters to accommodate
such variations in rates of drying.
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Proven acceptable ranges of processing parameters during primary and
secondary drying would be expected to yield some range of residual moisture.
This range would result from different variables of shelf temperature, chamber
pressure, as well as the conditions for desorption in secondary drying. The least
significant influence is often variations in time. However, depending on the
characteristics of the formulation and the association of residual moisture in the
product, the allowable range of time in secondary drying needs to be correlated
with the resulting residual moisture contents. This should be accomplished
during the developmental phase. Sequential stoppering or use of a sample extraction
device to determine the change in residual moisture content over time
is a convenient method for measuring the extent of moisture decrease. Another
method used during development activity to justify the time necessary in secondary
drying is generating a desorption isotherm. Examples, such as the
sorption isotherms for polyvinylpyrrolidone (PVP) have been presented [27].
Methods for conducting such studies have also been more recently described
[28].
6. Finished Product Attributes
There are unique dried material quality attributes associated with lyophilized
materials. The term dried material is used loosely here and meant to encompass
both lyophilized drug substances and intermediates, as well as drug products
intended for administration. Quality attributes are nearly identical for each type
of material, whether drug substances or finished drug products. Stringent microbiological
quality is also a requirement for sterile drug products, whereas an
acceptable level of bioburden might be appropriate for a bulk drug substance.
In addition to chemical or biological assay and specific requirements for
a finished product, such as those for parenteral administration, the condition of
the dried cake also needs to be identified. These include the physical appearance
of the dried cake and the ease with which the dried material goes back into
solution.
The results of a successful and effective freeze-drying process is the retention
of the physiochemcial attributes of the starting solution and, preferably,
retention of the structure established during freezing. Assay of the constituted
solution assures the preservation of the desired activity present in the starting
material. Assay of multiple samples of dried material is used to demonstrate
content uniformity.
Physical Appearances. The appearance of the dried material should be
uniform in structure, color, and texture. A material having ideal pharmaceutical
elegance would be a dense, white cake, with fine, uniformstructure as illustrated
in Figure 2. As described earlier, successful freeze drying results in the retention
of the structure established during the freezing step. If the material forms the
desired appearance upon freezing and that structure is retained throughout the
Copyright © 2003 Marcel Dekker, Inc.
Figure2 A cake that is uniform in appearance, texture, and color, occupying the original
volume of the liquid fill epitomizes a “pharmaceutical elegance” for a lyophilized
product.
drying, then the process should yield a finished product with an appealing appearance.
For some formulations, particularly those with low solids content, the
dried cake may shrink from the original volume on drying, as evidenced in
the sample in Figure 3. Such shrinkage is dependent on the concentration of the
starting solution, nature of the active ingredient, and the amount and type of
excipients used. However, the shrinkage is often uniform throughout the batch.
Although not always achievable, the design of an ideal formulation would lead
to a dense cake, uniform in color and texture, with good physical strength and
friability [29].
A decrease in total volume or localized loss of structure can also be associated
with a condition referred to as collapse [30]. This condition occurs when
the frozen or partially dried material exceeds the phase transition at which the
material may again become fluid. Samples of dried product in Figure 4 illustrate
the appearance of the cake structure caused by extensive collapse.
With the material becoming fluid, there is a loss of desired structure established
during freezing, often coincident with entrapment of water. This entrapment
of water into relatively larger masses may also prevent adequate desorp-
Copyright © 2003 Marcel Dekker, Inc.
Figure 3 The slight gap between the dried cake and the side wall of the vial exemplifies
shrinkage that may occur with some formulations. This shrinkage may be attributed
to either low concentrations or be characteristic of the materials in the formulation.
tion, resulting in a high residual moisture content. Reconstitution times may also
be lengthened because of a “case hardening” of the dried material.
Because the objective of this process is the preservation of the lyophilized
material, the presence of collapsed material is suspect. Collapse may simply be
considered a cosmetic defect. When the collapsed material exhibits an increased
reconstitution time or poor solubility, the presence of collapse becomes more
than just a cosmetic defect. If, however, the collapsed material retains a higher
amount of residual water, where this water becomes involved in degradation of
the product through hydrolysis, then there is a more serious concern. The presence
of a significant amount of residual water may promote degradation of the
product, such that the assay falls outside of the compendial limits. There would
also be a concern for the toxicity or an influence on the therapeutic effectiveness
of the product. Both potential results should be considered during product development.
Residual Moisture. For virtually all materials lyophilized, the primary
objective is removal of any water that would be chemically active during longterm
storage of the product. Any readily available water may become involved
in hydrolysis reactions, the common cause of degradation for lyophilized prod-
Copyright © 2003 Marcel Dekker, Inc.
Figure4 Loss of the initial structure during drying due to the product being warmer
than the phase transition temperature yields a varying amount of collapse. (a) A significant
change in the cake shape and structure is illustrated. (b) Extensive collapse with
minimal similarity of color and a dimensional proportion to the original cake. (c) Extensive
collapse to form granular masses at the vial bottom with a residue on the side wall
of the vial but without any recognizable similarity to the original cake.
Copyright © 2003 Marcel Dekker, Inc.
ucts. Therefore, this requires that a sufficiently low residual moisture content be
achieved. An acceptable level of moisture content, identified during development,
is the primary indication that the lyophilization process was successfully
completed.
The defined range suitable for acceptable stability may approach the variability
of the moisture determination method or may be as great as a few percent.
For example, many lyophilized products with the USP have a finished
product residual moisture specification of less than 2% of dry weight. Other
products, such as amphotericin B, have a residual moisture limit of 8.0% [31].
Whether the allowable residual moisture specification is small or large, a range
of acceptable residual moisture needs to be identified and correlated to suitable
long-term stability.
The analytical method for moisture determination must be validated before
use during process validation studies. There are numerous techniques for
moisture analysis that range from physical methods, such as loss on drying, to
chemical methods, such as Karl Fisher titration. A comparative review of the
conventional techniques are presented in an overview [32]. The measurement of
residual moisture is lyophilized pharmaceuticals by near-infrared (NIR) spectroscopy
has recently been expanded [33].
Reconstitution. Times required for reconstitution and the appearance of
the constituted solution are also of importance. The nature of the dried material
as a result of lyophilization often yields a product that is highly hygroscopic.
Reconstitution is often instantaneous on addition of the diluent. For ease of use
in a clinical setting, reconstitution times are often less than 2 min. Whatever
time is required to resolubilize that material, the constituted solution should be
clear and free of any visible particulates or insoluble materials, meeting the
compendial requirements such as those outlined within the USP [31].
The method of reconstitution is also important. For example, the package
insert for lyophilized somatropin indicates that during aspiration the diluent stream
should be aimed against the side of the vial. In addition, the constituted solution
should be gently swirled and not shaken [34]. Vigorous motion could result in
aggregation of the protein to form insoluble particles. For amphotericin B, vigorous
shaking is indicated until all of the crystalline material dissolves, forming a
clear, yellow colloidal dispersion [34]. Whether the solution solubilizes instantaneously
or requires special handling, forming a colorless solution or a colored colloidal
dispersion, the expected appearance of the constituted solution needs to be a
quality attribute established and supported by development data.
Assay. Analysis of the active ingredient, whether by chemical or biological
methods, would be the same for the constituted product as that necessary
for any ready-to-use preparation. Constituted solution, however, have a limited
shelf life after addition to the diluent. Depending on the solution stability, the
Copyright © 2003 Marcel Dekker, Inc.
package insert may indicate that the constituted solution be used immediately
after reconstitution, or it may be stored at selected conditions, often 2–8°C, for
a specified length of time. The stability of the constituted solution needs to be
established during development and measured as part of the stability testing.
The potency and purity must also be measured at the end of the indicated shelf
life. This includes not only the solution after initial reconstitution, but also after
storage at the conditions indicated for the constituted solution in the package
insert. Analysis should also include assay of any degradation product.
VIII. SUMMARY
Lyophilization is a complex unit operation, integrating multiple processing steps
with varied conditions for completing the preservation of the drug material. This
same process is applied to processing a relatively simple preparation for a drug
substance and a compound formulation for a finished drug product.
Lyophilization processes consist of the manipulation of environmental
conditions of subambient temperatures and subatmospheric pressures. These extraordinary
conditions are created by the lyophilization equipment. The success
of the process, therefore, relies heavily on the operating performance of the
lyophilizer. Confidence in the ability of the equipment to create these necessary
environmental conditions is achieved through the successful completion of a
comprehensive IQ and OQ. Without the proper performance of the equipment,
there is limited opportunity for successful processing of materials.
Throughout this presentation, emphasis is placed on the need to develop
an appropriate and adequate process. This includes challenging the process to
develop a proven acceptable range. The result of such an approach is a rugged
and robust process, yielding cycle conditions that are safe, effective, and preferably,
efficient. These processing conditions are demonstrated to be adequate and
appropriate, ultimately through finished product testing. Of equal importance,
this process is applied to preserve the quality of the material through processing
and throughout the shelf life. Demonstrating the process suitability also requires
correlating the process with product stability.
The behavior of the material during the processes is strongly dependent
on the characteristics of the starting materials. Their characteristics must also
then be measured and quantified. This includes not only the quality of the starting
raw materials and excipients, but also in the preparation and packaging
before placing the product into the lyophilizer.
Finally, how the characteristics and quality of the finished product are
quantified is of equal importance. This includes the physical attributes of the
dried material as well as the quality on reconstitution. The level of quality must
Copyright © 2003 Marcel Dekker, Inc.
extend beyond the time of initial testing for release of the batch to the final
expiration date.
When choosing constituents for lyophilization, select constituents based
upon their interactions during freezing, the primary drying processing and possible
reactions during secondary drying [35]. In addition, to remain properly lyophilized,
the product must be sealed within its container prior to removal from
the ultradry atmosphere that exists at the completion of the lyophilization cycle
[36]. The freezing method used during lyophilization can substantially affect the
structure of the ice formed, the water vapor flow during primary drying as well
as the quality of the final dried product. Controlling how a solution freezes
can shorten lyophilization cycles and produce more stable formulations [37].
Analytical tools for assessing the quality of freeze-dried pharmaceuticals have
been developed separately by Daukas and Trappler [38] and Nail et al. [39].
Finally, improvements in the design and construction of production size freeze
dryers, together with close attention to operating procedures have yielded dramatic
improvements in achieving a sterility assurance level (SAL) of 10?6 when
clean-in-place (CIP) and steam-in-place (SIP) methods have been employed
[40].
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(1984).
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McGraw-Hill, (1986).
5. Jennings, T. A. A model for the effect of real leaks on the transport of microorganisms
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6. The Parenteral Society (PS). Technical Monograph No. 7, Leak Testing of Freeze
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7. Greiff, D. Factors affecting the statistical parameters and patterns of distribution of
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8. Scheaffer, G., Sum, L., Trappler, E. Techniques in demonstrating batch uniformity
for lyophilized products. Presented at the Annual Meeting of the PDA, Boston,
Nov. (1995).
9. Day, L. Influence of vial construction and material on uniformity of product temperature
during freezing and freeze drying of model product formulations. Presented
at the Annual Meeting of the PDA, Boston (1995).
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10. Pikal, M. J., Shah, S., Senior, D., Lang, J. E. Physical chemistry of freeze drying:
measurement of sublimation rates by a microbalance technique. J Pharm Sci 72:
635–650 (1983).
11. Pikal, M. J., Roy, M. L., Shah, S. Mass and heat transfer in vial freeze-drying of
pharmaceuticals: role of the vial. J Pharm Sci 77:1224–1237 (1984).
12. Trappler, E. Scale-up Strategy for a lyophilized process. American Pharmaceutical
Review Fall 2001.
13. FDA. Proposed rules, Fed Regi, 61: 87 (1996).
14. Pikal, M. J., Lukes, A. L., Lang, L. E., Gains, K. Quantative cystallinity determinations
for beta-lactam antibiotics by solution calorimetery: correlation with stability.
J Pharm Sci 67:767 (1978).
15. Penner, G. Trappler, E. Effect of pH on the phase transition temperature of model
excipients. Presented at the Annual Meeting of the PDA. Philadelphia, Nov. (1990).
16. Korey, D. J., Schwartz J. B. Effects of Excipients on the crystallization of pharmaceutical
compounds during lyophilization. J Parenter Sci Technol 43:80–83 (1989).
17. Manning, M., Patel, K., Bochardt, R. T. Stability of protein pharmaceuticals. Pharm
Res 6:903–918 (1989).
18. Dubost, D., Kaufman, M., Zimmerman, J., Bogusky, M. J., Coddington, A. B.,
Pitzenberger, S. M. Characterization of a solid state reaction product from a lyophilized
formulation of a cyclic heptapeptide. A novel example of an excipient induced
oxidation. Pharm Res 13:1811–1814 (1996).
19. Orberholtzer, E. R., Brenner, G. S. Cefoxitin sodium; solution and solid-state chemical
stability studies. J Pharm Sci 68:863–866 (1979).
20. Pikal, M. J., Dillerman, K. M., Roy, M. L., Riggin, R. M. The effects of formulation
variables on the stability of freeze dried human growth hormone. Pharm Res
8:427–436 (1991).
21. Her, L., Deras, M., Nail, S. Electrolyte-induced changes in glass transition temperatures
of freeze-concentrated solutes. Pharm Res 12:768–772 (1995).
22. Brittain, H. G., Bogdanowhich, S. J., Bugay, D.E., DeVincentis, J., Lewen, G.,
Mewman, A. W. Physical characterization of pharmaceutical solids. Pharm Res 8:
963–973 (1991).
23. DeLuca, P.P., Boylan, J. C. Formulations of small volume parenterals. In: Avis,
K. E., Lachman, L., Liberman, H. A. eds. Pharmaceutical Dosage Forms: Parenterial
Medications, Vol. 1. New York: Marcel Dekker, 1984, p. 195.
24. Akers, M. J., Milton, N., Bryn, S. R., Nail, S. L. Glycine crystallization during
freezing: the effects of salt form, pH, and ionic strength. Pharm Res 12:1457–1461
(1995).
25. MacKenzie, A. P. Non-equilibrium freezing behavior of aqueous systems. Philos
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26. DeLuca, P. P., Lachman, L. Lyophilization of pharmaceuticals I, effect of certain
physical-chemical properties. J Pharm Sci 54:617–624 (1965).
27. MacKenzie, A. P., Rasmussen, D. H. Interactions in the water-polyvinylpyrrolidone
system at low temperatures, In: Jellinek, H. H. G. ed. Water Structure at the Water-
Polymer Interface. New York: Plenum Publishing, 1972, pp. 146–172.
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29. Bashir, J. A., Avis, K. E. Evaluation of excipients in freeze-dried products for
injection. Bull Parenter Drug Assoc.
30. MacKenzie, A. P. Collapse during freeze drying—qualitative and quantative aspects.
In: Goldblith, W.A., Rey, L., Rothmayer, W. W. eds. Freeze Drying and
Advanced Food Technology. New York: Academic Press, 1975, pp. 278–307.
31. USP 23 / NF 18, Rockville, MD: United States Pharmacopeial Convention, 1995.
32. May, J. C., Grimm, E., Wheeler, R. M., West, J. Determination of residual moisture
in freeze-dried viral vaccines: Karl Fischer, gravometric and thermogravimetric
methodologies. J Biol Stand 10:249–259 (1982).
33. Root, D. E., Leasure, R. M. Measurement of Residual Water by Near-Infrared
(NIR) Spectroscopic Analysis. PMPS Sept 2001.
34. Trissel, L. A., Handbook of Injectable Drugs. 8th ed. Amer. Soc. Hospital Pharm.
1994.
35. Jennings, T. A. Effect of Formulation on Lyophilization. IVD Technology Mar/Apr
1997.
36. Pearcy, T. E. Lyophilization Processing. IVD Technology May/June 2000.
37. Patapoff, T. W., Overcashier, D. E. Importance of freezing on lyophilization cycle
development Biopharm March 2002.
38. Daukas, L. A., Trappler, E. H. Assessing the quality of lyophilized parenterals.
Pharm Cosmetic Quality Sept/Oct 1998.
39. Nail, S. L., Schwegmani, J. J., Kamp, V. analytical tools for characterization of
frozen systems in the development of freeze-dried pharmaceuticals. Amer Pharm
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40. Stewart, P., Snowman, J. W. Recent advances in the cleaning and sterilization of
industrial freeze dryers. PMPS Dec 2000.
Copyright © 2003 Marcel Dekker, Inc.
10
Validation of Inhalation Aerosols
Christopher J. Sciarra and John J. Sciarra
Sciarra Laboratories Inc., Hicksville, New York, U.S.A.
I. INTRODUCTION
Inhalation aerosols have been used for the delivery of drugs to the respiratory
system since the mid-1950s. The most common dosage form for inhalation is the
metered-dose inhaler (MDI), by which the drug is delivered from a pressurized
container using a liquefied gas propellant. Medication delivered via this dosage
form has allowed for a quick therapeutic response to the symptoms of asthma,
emphysema, and chronic obstructive pulmonary disease (COPD), and has resulted
in an improvement in the quality of life for millions of asthma sufferers.
The metered-dose aerosol is considered to be a unique pharmaceutical
dosage form since the drug is delivered directly to the lungs [1,2]. It should not
be classified as either an oral dosage form, which generally is delivered through
the gastrointestinal tract, or a parenteral dosage form, which is administered
directly into body fluids or tissues. Metered-dose inhalers are classified as nonsterile
products but should exhibit lower bioburdens than are found in oral or
topical dosage forms. Since MDIs are nonaqueous systems they generally do
not support microbiological growth. This system is pressurized using chlorofluorocarbons
(CFCs) or hydrofluorocarbons (HFAs), thereby creating a selfpropelling
dosage form. As a result, different manufacturing and testing requirements
are involved during the validation phase of new product introduction.
A. Types of Metered-Dose Aerosols
Nearly all MDI products are intended for delivery through the oral cavity [3].
There are a few products that are intended for administration via the nasal cavity,
however. There is also a metered-dose aerosol for administration sublin-
Copyright © 2003 Marcel Dekker, Inc.
gually. The site of administration will determine the type of actuator or adapter
used in combination with the aerosol canister. Metered-dose inhalers are unique
in that in addition to drug formulation, the entire packaging is critical for the
correct administration of the medication. Figure 1 shows the basic components
of an MDI system.
The medical use of metered-dose aerosols is usually for bronchial asthma
or COPD. The drugs used represent different classes of therapeutic agents. Betaadrenergic
agents and the more selective beta2-adrenergic agents are the commonly
used bronchodilators for the rapid relief of asthmatic symptoms. Corticosteroids
help reduce edema and inflammation and are usually prophylactic in
activity. Anticholinergic compounds and a mast cell inhibitor are also available
in MDI form for the symptomatic treatment of asthma. Other therapeutic uses
for MDIs include systemic activity, such as vasodilatation (nitroglycerin) and
antimigraine (ergotamine).
There are two general types of formulations. First, the micronized active
ingredient may be suspended in liquefied propellants (CFCs or HFAs). This group
makes up the most common type of MDI. Second, the drug may be dissolved in
a mixture of CFCs or HFAs and ethanol, forming a solution. Less than 25% of
MDI products are formulated as solutions developed over 50 years ago.
Fewer than 12 different excipients in MDI products have been formulated
into metered aerosols. The availability of established FDA-approved excipients
limits the formulator to a select few such ingredients. Table 1 lists excipients
and the approximate amounts of some of these excipients that are currently used
in MDIs. Metered-dose inhalers formulated with CFCs contain propellant 12,
propellant 12/11, propellant 12/114, or propellant 12/114/11. These propellant
Figure 1 Typical metered-dose aerosol delivery system.
Copyright © 2003 Marcel Dekker, Inc.
Table 1 MDI Inactive Ingredients
Type Ingredient Amount (%)a
Propellants CFCs 11, 12, 114 60–99
HFAs 134a, 227ea
Dispersing agents Sorbitan trioleate 0.01–0.8
Sorbitan sesquioleate 0.01–0.8
Oleic acid 0.01–0.8
Soya lecithin 0.01–0.1
Cosolvent Ethyl alcohol 2–38
Water 5–10
Antioxidants and flavors Ascorbic acid 0.1
Saccharin N/A
Menthol N/A
Antimicrobial Cetylpyridiniurn chloride N/A
aApproximate amounts derived from package inserts and literature; N/A = not available.
systems are required for proper dispensing of the MDI. Metered-dose inhalers
formulated with HFAs contain either propellant 134a or 227 or mixtures of
these two propellants.
1. Solution MDIs
Older drugs such as isoproterenol hydrochloride or epinephrine hydrochloride
were formulated as aerosol solutions, with the drug solubilized in a chlorofluorocarbon–
ethanol–water system. These aerosol solutions contain 30–38% (w/
w) ethanol as a cosolvent and other additives to mask the poor aftertaste of the
ethanol. Menthol, saccharin, and flavors are all currently used in some of these
marketed products. Newer MDIs using HFA propellants are being formulated
as ethanolic solutions. These MDIs contain 5–20% (w/w) ethanol as a cosolvent.
These HFA-formulated solutions are unique in that the drug dissolved in the
volume of ethanol is much more concentrated (10–50% w/w) than the CFC
formulations containing ethanol, and a low concentrate (drug plus ethanol) is
added to the container. Antioxidants such as ascorbic acid are also used to enhance
the drug’s stability in solution form.
2. Suspensions
The active ingredients in MDIs are usually water-soluble and chlorofluorocarbon-
or hydrofluorocarbon-insoluble. Some CFC and HFA formulations use ethanol
as a suspending agent by using an ethanol-insoluble salt form of the drug.
Since the vehicle in MDIs must be propellant-based, a product with the drug
suspended in the propellant may be the most stable dosage form.
Copyright © 2003 Marcel Dekker, Inc.
Nearly all suspension products contain a dispersing or suspending agent
to facilitate wetting of the drug during manufacture of the suspension. All MDI
suspensions with two exceptions contain sorbitan trioleate, oleic acid, or soya
lecithin, all of which have surface-active properties. An MDI containing triamcinolone
acetonide does not contain a typical dispersing agent but does contain
a small amount of ethanol. These ingredients also have a lubricating action on
valve components, although experimental studies have shown that they may be
unnecessary for their proper functioning [4].
Suspensions contain micronized drug for proper delivery to and absorption
in the respiratory system. Typical particle size of the micronized drug is from
2 to 5 microns [5]. Aerodynamic mean particle size as measured by cascade
impactor or direct method of microscopic analysis is usually from 0.5 to 4
microns [5]. Additional particle-sizing techniques such as light scattering can
be used [6].
The amount of drug in marketed products varies from 10 micrograms to
800 micrograms per actuation, as delivered from the actuator or mouthpiece.
The amount of drug administered to the patient is small relative to that delivered
in other dosage forms. Potent drugs are thus utilized and should have special
care during raw material handling and manufacturing.
Most of the contents are delivered in the proper dosage in a filled aerosol
canister. It is important to recognize, however, that some nonsprayable formulation
remains in each filled unit. Each filled canister will deliver at least the
labeled number of doses, and the actual can contains an overage to ensure delivery
of the labeled number of doses. As an example, Figure 2 shows the approximate
doses found in a 20-g filled unit.
In this example, if the average of the metered spray weighs 70 mg, then
an average of 250 metered doses per canister will be obtained (sprayable 17.5
g). The nonsprayable contents (2.5 g) are derived from (1) propellant vapors in
the can when empty of the liquefied portion, (2) allowance for filling variation
leading to slight underfilling of contents during manufacture, (3) leakage of
Figure 2 Approximate disposition of a 20-g filled unit.
Copyright © 2003 Marcel Dekker, Inc.
propellant during the life of the unit, and (4) partial sprays (tail-off) due to
incomplete filling of the valve chamber when the can is nearly empty. Any
residual drug remaining in the unit is a negligible amount on a weight basis—
less than 0.01 g—compared to the other items. The losses indicate why larger
overages are used for this type of dosage form compared to an injectable drug.
B. Manufacturing
Two methods for filling aerosol MDIs are used today—cold filling and pressure
filling [5,7]. These methods describe the manner in which the propellant is
added to the can or plastic-coated glass bottle. Solution or suspension formulations
may be filled by either method.
In cold filling, the ingredients (including drug, suspending agents, excipients,
and all propellants) are mixed and chilled to about ?30 to ?60°F prior to
adding to the empty container. Filling occurs at temperatures well below the
mixture’s boiling point and before the valve is inserted onto the canister.
In pressure filling, only concentrate-containing drug, high boiling propellant,
ethanol, and other excipients are filled before valve crimping. The low
boiling propellant (CFC 12, HFA 134a, or HFA 227ea) is added after the valve
is crimped onto the container. The propellant, usually at room temperature, is
added through the valve stem under high pressure (300 to 600 pounds/square
inch gauge [psig]).
Typically CFC products utilize both the cold-fill and the pressure-fill processes.
Whether a product is filled by pressure or cold, is determined by the
manufacturing equipment available at a particular company and by the nature
of the active drug. For example, since Albuterol is moisture-sensitive, it cannot
be filled by the cold process. Hydrofluorocarbon products are typically filled
using the pressure-filling method. Figure 3 depicts the process flow, indicating
both types of fillings.
Since metered-dose aerosols are not claimed to be sterile products, filling
of the product does not require rated clean room standards as described in U.S.
federal standard 209C. Frequently, however, high-efficiency particulate air
(class 100,000) is employed above any open tanks and filling lines. This practice
is used to reduce the likelihood of particulate and microbial contamination in
the product.
II. RAW MATERIALS
A. Ingredients
In aerosol dosage forms, the micronized active ingredient, suspending agent,
CFC, and HFA propellants are usually the most crucial raw materials. Other
additives such as antioxidants or flavors may also be crucial.
Copyright © 2003 Marcel Dekker, Inc.
Figure 3 Types of aerosol filling.
1. The Active Pharmaceutical Ingredient
The important characteristics of the active pharmaceutical ingredient (API) are
impurities, degradation products, water content (if hygroscopic), particle size
[8], static charge, crystallinity, polymorphism, and microbial content. The milling
or micronization process parameters should be recorded with micronized
APIs. The finished product characteristics of the MDI may be related to the API
(e.g., particle size). A reproducible drug particle size distribution [9], along with
a validated manufacturing process, ensure lot-to-lot consistency of the final
product. In addition, an acceptable water content of the drug substance prevents
changes in agglomeration, crystallinity, or stability. Any additional tests performed
on the active ingredient that are nonroutine release tests (e.g., X ray,
diffraction, differential thermal analysis [DTA], or particle size) may be carried
out for information purposes. Any specific test method used that was not part
of the bulk drug testing specifications needs to be documented. For example,
particle size or moisture content determined by a second method should be
added to the validation report, along with the specific methods used. Reference
samples of bulk drug should also be established. This may be of benefit in
evaluating any future test methods.
Copyright © 2003 Marcel Dekker, Inc.
2. Propellants
The propellants used in MDIs are trichloromonofluoromethane NF (CFC 11),
dichlorodifluoromethane NF (CFC 12), dichlorotetrafluoroethane NF (CFC 114),
tetrachloromonofluoroethane (HFA 134a), and heptafluoropentane (227). Currently
marketed MDIs containing a CFC can continue to be marketed. The use
of CFCs in new MDIs is prohibited except in certain essential uses in which an
HFA propellant cannot be used. At a minimum they should meet compendial
grade specifications. A single supplier should be preferred and used in the validation
lots. Handling and storage techniques, such as temperatures, tank type,
size, and headspace, should be noted for the propellants. Any blends of CFCs
or HFAs used as a raw material for MDI manufacturing, whether purchased
or prepared in-house, must meet assay specifications of each CFC or HFA.
Specifications of a mixture such as water content or other compendial tests may
also apply [10]. Assays and tests similar to compendial methods are needed
until a satisfactory history of that supplier can be established. Table 2 lists key
physical properties [11] of the five MDI propellants. The propellants used in
MDIs are usually shipped in steel cylinders or drums and are under pressure.
They may be stored outdoors before or during aerosol manufacture, provided
temperature effects are controlled. It is industry practice to filter propellants
before compounding or filling to ensure against particulates. The 0.22- or 0.45-
µm (nominal) “solvent-grade” Teflon, Nylon, mixed cellulose acetate, or polyvinylidene
difluoride (PVDF) filters are reported to be compatible with CFCs and
HFAs. These filters are used to remove particulates of micrometer or submicrometer
size. Pharmaceutical sanitary housings and setups are preferred, and all
contact parts such as O rings must be nonreactive to fluorocarbons. Cartridgetype
filters are more common because of their ease of use and desirable flow
rate. Fractionation of propellant mixtures inside a storage tank or cylinder must
be monitored [12]. This occurs when the propellant with the higher vapor pres-
Table 2 Key Physical Properties of Propellants for MDI Products
Vapor
Molecular Boiling point pressure (psig) Density
weight (°C) at 21.1°C (g/ml)
Trichloromonofluoromethane (P-11) 137.4 23.7 ?1.3 1.485
Dichlorodifluoromethane (P-12) 120.9 ?29.8 70.3 1.325
Dichlorotetrafluoroethane (P114) 170.9 3.6 12.9 1.468
Trifluoromonoflurothane (P-134a) 102 ?27 71.1 1.21
Heptafluropropane (P-227) 170 ?17 43 1.41
Copyright © 2003 Marcel Dekker, Inc.
sure fractionates into the vapor headspace in a container, leaving a lower proportion
in the liquid phase. When the liquid is pumped for filling it would then
have an undesirable composition. Different pressures would result, and thus
measuring container pressure may be a way to monitor fractionation within the
propellant tank.
Sampling techniques for propellant mixtures should be performed rapidly
to prevent vaporization of any of the propellants. Some techniques include; using
prechilled cans, dipping with ladles, and crimping on the spot. Condensation
of moisture onto the container and into the propellant must also be considered.
3. Suspending Agents
Suspending agents may have special requirements, such as specific storage and
stability requirements. An example is soya lecithin, which is sensitive to light
and air causing degradation into an odorous, discolored substance. Other natural
products similarly need careful evaluation. Short-term expiry dates of 6 months
may be best for unstable suspending agents. Special sampling programs for
these materials might be extended to test for drum-to-drum variability within a
lot of these types of raw materials. Sorbitan trioleate NF, oleic acid NF, and
lecithin NF must meet their compendial requirements.
4. Cosolvents
The grade of alcohol used should meet the tests for alcohol USP. The amount
of water may be critical, since MDIs are typically nonaqueous systems.
5. Miscellaneous
At a minimum, other inactive ingredients used in the product should meet compendial
requirements. These include ascorbic acid USP, ether USP, menthol
USP, saccharin NF or USP salts of saccharin, and flavors.
B. Package Components
The packaging components of the multiple-dose MDIs are an integral part of
the dosage form. Consistent delivery depends on the proper functioning of the
valve throughout the use of the unit. The fit of the valve and actuator can also
influence the drug delivery. If possible, obtaining the valve and actuator from
the same vendor permits the vendor to test the combination in addition to the
individual components, minimizing the chance for improper function of the
combination of components.
Copyright © 2003 Marcel Dekker, Inc.
1. Metered Valves
As with other packaging components, the incoming tests and specifications of
metered valves, inspection attributes, and AQLs (acceptable quality levels) will
need to be coordinated with the supplier. The valve should be considered as a
critical package component and have incoming performance tests, such as spray
weights and weight loss [13,14]. The performance test could be conducted on a
sample of the valve lots from either scale-up or pilot trials before the validation
lots are prepared. This information may also be available for each lot from the
supplier. It is recommended that each test shown in Table 3 be conducted on at
least three valve lots as part of the validation program.
The metered valves should be well characterized before beginning the
process validation lots. The typical performance attributes, such as spray weight
variations within and between valves of a single valve lot, spray weight variation
between valve lots, leakage, crimp dimensions, and incoming inspection
criteria, should be well known. In addition, the loss of prime [15] and singleshot
assay data [6,16] should be generated during the development stage. Additional
characterization of the valve done during development involves gasket
extractables, compatibility with valve componentry [6], and particulate cleanliness.
The metered valve crimped on an aluminum can (anodized or plastic
coated) glass bottle creates the uniqueness of the MDI dosage form. The dimensions
of the valve parts related to the crimp, such as ferrule and gasket thickness
Table 3 Important Valve Tests Per Lot
Number
Test of valves Characteristics
Inspection for attributes MIL-105E Appearance, identity, proper
assembly
Dimensional check 40 Proper components, identity
Valve delivery (spray weights), 40 Meter chamber size, in-use test,
mean, RSD meter chamber variability
Valve delivery at labeled num- 6 Ruggedness of multiple sprays
ber of actuationsa
Weight lossa (leakage) 12 Sealing capability, proper
rubber sealability
Loss of primea 12 Meter chamber sealability
Particulatesa 12 Valve cleanliness
Extractablesa 12 Rubber contaminants
aTested for information; not part of routine testing of all valve lots.
Copyright © 2003 Marcel Dekker, Inc.
may thus be critical in the finished package. Other critical dimensions are related
to the metering chamber size for dosage reproducibility, stem dimensions
for mouthpiece fitting, orifice sizes for meter chamber refilling and pressure
filling rates, and stem stroke length or travel for spring resilience.
All valves contain rubber components (gaskets, tank seals, seats, or
sleeves) and at least one stainless steel part (spring). Both are vital to valve
functionality. Some types of valves contain more plastic or stainless steel components
than others. Drawings of individual subcomponents of the valve should
be on hand for reference to the incoming components. Periodic checking of the
rubber or other components may be needed to ensure that the supplier has not
changed any compositions or processing procedures.
The normal rejection rate during a 100% spray testing step such as percentage
of no-sprays and continuous sprays would be helpful before validation.
Should any deviations occur during the process validation lots, it is imperative
to determine the cause of the deviation. If it involves leakage, spray weight,
crimp appearance, or other attributes related to the valve, then the incoming
component testing of the valve will be helpful. The component release test results
should be reviewed and compared to the finished product testing. As stated,
the incoming tests may be evaluated on pilot equipment or from scale-up lots
using actual drug formulation. Alternatively, if it has been demonstrated that the
drug has an insignificant effect (such as less than 0.2% drug of a suspension
formulation) on valve performance for release testing, a placebo may be used
to test incoming valves. Only after significant historical validation should the
testing scheme in Table 3 be reduced.
It is imperative to also consult the vendor to determine an adequate number
of valves for spray weight testing. If the metered chamber is plastic, valves
totaling at least twice the number of the vendor’s mold impressions should be
tested to guarantee complete evaluation of the lot of valves. The spray weight
methodology conducted on valves can drastically influence the results. Because
the valve is a mechanical device, the way in which it is actuated is techniqueoriented.
Manual actuation versus automatic actuation can cause variation in the
results. Method ruggedness is essential in evaluation of the valve performance.
Leakage of the propellant through the valve is a critical parameter. Although
the test is not required for metered valves in the USP, the leakage rate
should be well characterized for leakage during development [6].
Valves may have special shipping or storage requirements. For example,
some valves are shipped in hermetically sealed bags to prevent moisture adsorption
to plastic or rubber parts. Others are shipped in plastic pails. Any expiration
period of the valve must be known. Expiration periods result from the aging of
the rubber componentry, which causes the rubber parts to lose their sealing or
resilience, affecting spray weights and leakage.
Copyright © 2003 Marcel Dekker, Inc.
2. Aluminum Can or Plastic-Coated Bottle
The drawing of the can or bottle should be on hand at the manufacturing site
as part of the validation package. The drawings should specifically state the
following:
1. Drawing number and date
2. Supplier code number or part number
3. Type of materials used (e.g., aluminum 5502, glass type)
4. Chemical treatments or coatings (e.g., glass treatment, aluminum anodizing,
epoxy lining)
5. Container dimensions
a. Heights and widths, inside and out
b. Wall thickness
c. Neck and bottom curvatures and radials
6. Empty can or bottle weight
7. Special imprints or lettering (label copy, if preprinted can)
8. Any revisions to the drawings
The can may have had special cleaning procedures at the supplier’s location
prior to receiving. Testing of cans on incoming inspection usually involves
identity, attributes, and dimensional checks. During development, any special
coatings may require a chemical test such as pH or acid resistance. Key dimensions
are usually related to the neck configuration, since slight changes may
affect the integrity of the crimp and subsequent leakage.
3. Mouthpieces
Oral adapters, mouthpieces, or actuators are made of plastic polyethylene or
polypropylene. As with the can requirements, drawings should be part of the
validation package. Frequently this component is omitted from validation protocols
of filled, crimped aerosol cans. This piece is critical to the functionality of
the unit, however.
A validation program should be developed for the finished assembled
package unit. All MDIs in the United States are packaged in one box with the
can and mouthpiece preassembled and the canister placed inside the mouthpiece
ready for use. A dust cap is provided to cover the end of the mouthpiece, which
is in contact with the lips.
An incoming inspection and performance testing program should be in
place for the mouthpiece. Some of the critical dimensions of the mouthpiece are
the design configuration, valve stem and mouthpiece coupling, spray orifice
size, and spray angle. The performance of a mouthpiece may be evaluated by
measuring the spray pattern emitted from adapter. This is usually performed by
Copyright © 2003 Marcel Dekker, Inc.
thin-layer chromatography [17] or video imagery [18,19]. The durability of the
mouthpiece should also be checked as a kind of in-use test. Instructions to patients
usually include washing the mouthpiece daily with water. This is to prevent
buildup of residue near the orifice, which prevents adequate delivery of
dosage or clogging. The type of buildup may be a unique characteristic of that
particular product. The mating of the mouthpiece and valve stem is also important
to the integrity of the package.
4. Auxiliary Device
Auxiliary devices such as tube spacers are available for use by the patient. Some
examples are Inspirease and Inhalaid devices [20]. Since they are provided separately
from the MDI to the patient, they should not be considered part of the
process validation. One such product however, triamcinalone Acetonide MDI,
is fitted with its own spacer, and in this case the spacer is considered to be an
integral part of the product.
III. MANUFACTURING
A. Concentrate Preparation
1. Suspensions
During a cold-filling operation, the suspending agent, micronized drug, and high
boiling propellant (CFC 11 and/or 114) are mixed, forming a concentrated drug
suspension. Mixing may be done by an impeller, turbine, or homogenizer-type
mixer. The mixing conditions utilized throughout the process validation lots
should thus be well documented. These include mixer details, position in the
tank, speeds, direction, and recirculation conditions (if used). The mixers used
should have qualification reports describing the design and performance details.
For compounding, jacketed stainless steel tanks capable of airtight sealing
are frequently used. The temperature of the drug preparation should be monitored
and sufficient to prevent evaporation of the propellant. Extremely low
temperatures, especially in a room with high humidity, may lead to condensation
of atmospheric moisture on recirculation lines, on filling equipment, or possibly
within the tank. Some of this ice may chip off filling nozzles and fall into the
canister. Nitrogen gas is thus usually used to blanket the head space before
and during concentrate preparation. Gas flow rates, nozzle positions, and other
conditions in the tank should be recorded. Temperatures above 55–60°F may
be too high if the drug concentrate requires greater than 1 hr preparation time.
In these cases temperature fluctuations could lead to evaporation of the high
boiling propellant (which boils at 75°F). This evaporation will increase the drug
concentration, resulting in a change in drug dispensed/actuation.
Copyright © 2003 Marcel Dekker, Inc.
Mixing tanks are preferably set on load cells or scales to ensure accurate
weighing of the volatile propellants and drug concentrates. Any evaporation or
loss of propellant can thus be monitored. Without a means of obtaining the gross
tank weight for the concentrate, accurate in-process assays will be required to
verify any loss of propellant. In suspensions, some drugs are easily dispersed,
whereas others require extensive mixing. If a homogenizer or colloid mill is
used, these conditions will also require documentation. The drug concentrate
may be filtered through an appropriate sized filter in order to assure an aggregate-
free suspension. This may not be needed if validation testing shows no
aggregate particles be present.
2. Solutions
Since solution aerosols contain ethanol as a cosolvent in order to render the
drug soluble, the ethanol and propellants are mixed and drug is added. The
concentrate solution may also include high boiling propellants [21]. Temperatures
must be low enough to assure minimal evaporation rates during filling but
also enable suitable dissolution of ingredients. Temperatures from ?50 to +5°C
have been used [21]. The propellant blend must provide sufficient vapor pressure
to propel the contents for inhalation, usually 35 to 60 psig (at 21°C). Higher
pressures are also used (CFC 12, HFA 227, or HFA 134a alone, 60 to 70 psig
at 20?C).
3. Types of Filling Equipment
In filling MDI concentrates, usually amounts of about 1 ml to 15 ml are added
to the canister. The filling equipment consists of either gravity filling with timed
microswitches or positive piston fillers. Piston fillers are used on such units as
Pamasol filling equipment. Product added by gravity filling may be controlled
by nozzle size and time. Gravity filling is usually best for volumes of 2 ml or
greater. Piston filling is controlled by piston size, bore size, and length. This
method is usually very accurate and precise. It may be necessary to shroud the
filling area with nitrogen to prevent moisture condensation on the filling equipment
and nozzles. Equipment may be fabricated to prevent outside atmospheric
moisture from entering. Nitrogen flow rates should be monitored as part of the
process validation protocol.
B. Propellant Filling
1. Cold-Fill Method
The propellant in cold-fill products almost always is a mixture of CFC 114 and
12 with or without propellant 11. Chlorofluorocarbon 114 reduces the vapor
pressure of 12, enabling it to be cold filled at higher temperatures without the
Copyright © 2003 Marcel Dekker, Inc.
loss of propellant. Mixtures of CFCs 114 and 12 may be added to the drug
concentrate containing CFC 11 and then filled into the can or bottle, or may be
cold filled separately after the drug concentrate is added. Propellant 134a or
propellant 227 may also be filled by the cold-fill method.
2. Pressure Fill
During pressure filling, the propellant or propellant blend may be pressure filled
alone or in combination. Pressure filling requires two filling steps, drug concentrate
and propellant filling. Figure 4 shows a schematic sequence of MDI manufacture
[22]. Tolerances must be established for each filling stage—control limits
for adjustment and tolerance limits for acceptance or rejection. In-process
check weights are usually performed at specified time intervals during validation
to verify the accuracy of filling. Control charts are then assembled for each
filling operation of each validation batch. Upper and lower limits are usually
clearly marked for simplicity. For a two-step filling operation with drug concentrate
followed by propellant filling, the acceptable drug concentration in the can
may be used to calculate acceptable filling amounts. For example, a lower limit
of drug concentrate fill and an upper limit of propellant fill will provide the
lowest possible final drug concentration. The specifications can be determined
for the suspension of the filled can to be within 90 to 110% of the label claim.
In this example, a concentrate fill of 1% drug (50 mg/5.00 g) provides a final
can potency of 2.50 mg/g. It is important that the specifications, equipment, and
fill quantities be coordinated so that limits are attainable. The original fill
amounts and ratios of propellants should be formulated in such a way that
ranges of acceptable concentrate and propellant are adequate.
Since more than 99.99% of filled cans would be within four standard
deviation units of a normal distribution, four standard deviation units appear to
be an acceptable target for fill-weight variations. The concentrate filler should
exhibit a relative standard deviation of less than 2.0%, one-fourth of the 8.0%
upper and lower limits of the concentrate fill. Figure 8 depicts an example of
concentrate fill target of 3.89 g and specification of ±0.23 g (5.9%). The propellant
fill should have a relative standard deviation (RSD) of less than 1.5%, onefourth
of the 5.9% limit. Tightening either the propellant or concentrate filler
will allow loosening of the second fill limits while maintaining the same specifications
of the final product.
3. HFA Filling (Single-Stage Filling)
With the introduction of HFA propellants as replacements for CFCs in MDIs,
both the cold-fill and pressure-fill processes have been modified. Both solution
and suspension formulations have been developed. Solution MDIs are filled, as
has been previously indicated. For suspensions (and solutions as well), however,
Copyright © 2003 Marcel Dekker, Inc.
Figure 4 Schematic production sequence for the manufacture of metered-dose inhalers
by pressure filling: (1) suspension mixing vessel; (2) can cleaner; (3) can crimper and
filler; (4) check weigher; (5) can coder and heat tester; (6) priming and spray testing; (7)
labeler; (8) feeds for tested cans and actuators. (Courtesy of Ellis Horwood Publishers,
Ref. 10.)
Copyright © 2003 Marcel Dekker, Inc.
the formulation (drug with or without any excipients, dispensing agent, etc.) is
added to a pressure tank capable of withstanding at least 150 psig at room temperature.
The tank is sealed and the entire amount of propellant (CFC or HFA) is
added under pressure. The entire mixture is then agitated until the drug is completely
dissolved or suspended in the propellant. This mixture is then fed to a
filler where a canister (previously cleaned, purged, and crimped with a metered
valve) is filled through the valve stem with the propellant. This is referred to as
single-stage filling. The equipment is made to flush any drug or propellant remaining
in the valve stem into the canister. Each stage of the process must be validated
to ensure that the finished product meets all specifications.
C. Crimping
The crimping station on an aerosol line occurs after the valve has been placed on
the canister. The valve may have been placed either manually or with automatic
equipment. Crimping should occur as soon as practical after filling and valve
insertion to minimize air entrapment and propellant vaporization. During crimping,
the ferrule of the valve is compressed by closing the jaws on the collet,
crimping the valve under the neck of the can or bottle. Crimping parameters and
measurements are recorded during process validation to verify the suitability of
the crimping process [23]. An adequate crimp is needed for acceptable leakage,
appearance, valve function, and propellant filling. Crimping parameters are usually
Head pressure (downward pressure exerted on the top of the valve)
Collet pressure (of closing collet)
Pad pressure (if this type of equipment is used)
If the crimp settings are stressed to extremes during development, corresponding
acceptable limits may be established. For example, the collet pressure
would be increased in stages to a point of unacceptable appearance or leakage. The
height or diameter of the crimp would also be determined for the different settings.
Before limits are finalized, several lots of valves and cans will have to be measured,
since these components have an effect on the final crimp measurement. Critical
crimp measurements taken on the crimped valve are described below.
1. Height or Depth of Crimp
The height of a crimp is measured from the top of the crimp jaw marks to the
top of the ferrule. The height of the crimp should be correlatable to the leakage.
When the height is too large, the valve has been improperly seated and leakage
may be excessive. If the height is too small, excessive pressure may have been
applied during crimping, affecting the valve function or appearance. Usually,
crimp height values are 6.5 to 7.5 mm (0.26 to 0.30 in.). The tool for measure-
Copyright © 2003 Marcel Dekker, Inc.
ment is calipers or another specialized device, such as a Socoge gauge for measuring
the depth of a crimped valve at a constant 19-mm radius.
2. Diameter or Radius of Crimp
This measurement is taken from one point on the crimp circumference to the
other point at 360°. The diameter is correlated to the pressure applied on the
jaws during closing of the collet. The usual values are 17.5 to 18.5 mm for a
valve and can with 20-mm uncrimped diameters.
3. Roll Off
Measurements taken of the top of the ferrule to the bottom of the can at four
locations 90° apart indicate the uniformity of pressure applied to the valve during
crimping. The difference between the highest and lowest of the four values
is called roll off (or run out). The results should be small (typically less than
0.1 mm).
4. Gasket Compression
This indicates the percentage of compression of a sealing gasket on the crimped
unit. The rubber gasket is compressed a certain percentage, enabling a seal to
occur between the ferrule of the valve and the can. It is determined by subtracting
uncrimped gasket thickness form the crimped unit thickness. The crimped
unit gasket thickness is measured by subtracting parts from the crimp height
after disassembly of the filled unit.
j? = H ? (2 ? e) ? h ? (1)
Here H, h?, and e are measured dimensions of the valve as defined in
Figure 5. For example, a crimped unit of height H of 7.00 mm, ferrule thickness
e of 0.36 mm, and can neck height h? of 3.85 mm yields a crimped gasket and
rim thickness j? of 2.43 mm. If the before-crimp gasket and rim thickness j is
3.04 mm and only the gasket of thickness 1.26 mm has compression, the compression
is 48%. In other words, the gasket has compressed 0.61 mm (3.04 to
2.43 mm) of 1.26 mm.
For valves with O rings the gasket compression is more difficult to measure.
Gasket compression has also been correlated to leakage, where a decrease
in the leak rate occurs with increase in gasket compression.
5. Can Deflection
The aluminum cans are deflected a small distance from their original height
during crimping when a high pressure is exerted downward. Deflection is measured
by carefully removing the valve of a crimped unit with pliers and measur-
Copyright © 2003 Marcel Dekker, Inc.
Figure 5 Gasket compression and crimp depth measurements (Socoge gauge).
ing the height of the deflected can compared to an uncrimped can. A Socoge
gauge may also be used to measure deflections at a constant 19-mm diameter
(h? in Fig. 5).
6. Appearance
The crimp should be aesthetically pleasing and free from exposed or sharp edges
at the end of the valve. It should tightly fit the contours of the can.
D. Leak Testing
All filled aerosol cans are leak tested before distribution to prevent an empty or
near-empty product from reaching the patient. Four methods are currently used
for leak testing.
Copyright © 2003 Marcel Dekker, Inc.
1. Hot water baths are maintained at temperatures above the boiling
point of the product, such as 100°F. More common temperatures are
120–130°F, since the time to raise the can contents would be shorter.
At least 1.5 to 3 minutes are required to bring the can contents to a
temperature that would emit propellant vapor in a leaky unit. Cans
are examined visually by inspectors who look for the presence of
faulty crimps, valves, and so on. The emergence of bubbles signifies
a probable reject. Protection from possible dangerous discharges
should be taken. Filtered tap water has been used to test for leakage
because the water does not come into contact with drug product. Currently
companies are trying to use recirculated and filtered purified
water in combination with ultraviolet lamps to minimize the microbial
bioburden in the water. Various types of defects usually arise from
poorly crimped valves (process defect), where bubbles appear from
the side of a valve skirt or ferrule. Other rejects may be due to poorly
assembled valves (valve defect), where leakage from the side of stem
may occur.
2. Induction heaters, in which cans are quickly heated and check
weighed at a later time [24], heat the units instantaneously on the
aerosol line after filling and crimping. Any faulty units or poor crimps
would burst upon testing and be removed from the line. Subsequent
check weighing is usually performed and any intact units that are
leakers are removed. Induction heaters were introduced as an improvement
over the visual inspection method. Storage of the filled
units for a set period of time has become the most commonly used
method for leak testing. Units are held for a sufficient period of time
so that leakers will fail a subsequent check weighing step. Fourteen
to 28 days have been used to ferret out faulty units [22]. Inventory
considerations have to be taken into account with this process requirement.
Also, the probability that slow or latent leakers will pass undetected
must be considered.
3. Storage for a predetermined time period before check weighing.
4. Pressure readings are designed to check the integrity of componentry
before filling. This was designed to check the tightness of the crimp,
which could be used later for performance evaluation.
E. Check Weighing
This step is commonly carried out to ensure that all cans reaching the consumer
contain an adequate supply of medication [25]. This may be conducted on units
after filling or leak testing but must be done before secondary packaging and
distribution. In setting the limits of the check weigher, the allowable fill weight
Copyright © 2003 Marcel Dekker, Inc.
variation and component weights must be factored in. The check weigher must
have low tolerances (usually less than 100 mg), well within the ranges of the
filled aerosol unit. Units filled with a known weight of steel beads may be used
to set the upper and lower limits. The rate of the check weighing step and the
set limits, along with the number of high and low rejects, should be tallied
during validation. Random units (failed and good product) may also be individually
weighed to verify the accuracy of the check weigher. Histograms may be
generated over a period of months for characterizing the expected leakage during
development. These are then compared to histograms of the same cans that
were generated immediately after manufacture.
F. Spray Testing
This step is performed on all filled units to remove any defectively spraying
MDIs such as no-sprays or continuous spray units. Two general methods are
used today, an automatic method and a manual method. The automatic unit may
employ different techniques, such as light or sound. For example, the sounds of
acceptable and unacceptable actuations are programmed and used for testing.
Continuous or no-spray valves will sound different from a single-fire acceptable
valve.
The presence of a powder as an aerosolized mist may be used so that
testing will be by an electronic eye. Manual methods include listening devices
for sound inspection or sprays for visual inspection of sprays. Hoods or spray
booths are used online where inspectors manually actuate units and observe for
defective sprays. Manual actuation for sound may be performed into vacuum
setups with microphones that amplify the valve actuation noise. The usual number
of actuations for testing is between three and five. At least two are considered
as priming shots, followed by a test fire. Rejection rates vary from lot to
lot and supplier to supplier but are usually less than 0.1%. The rejection rate,
classified by defect, and the testing method should be documented for the validation
lots. Rejected units should be closely examined for any false results and
may be used to improve the valve manufacturer’s quality control.
IV. VALIDATION PROTOCOL
A. Development Report
A development report should be written prior to the process validation protocol
by the research and development group and will serve as the basis for items to
be included in the validation protocol. Parameters such as process limits, formulation
compatibility with process equipment, time limitations of production, and
any problems encountered and their resolution, should be addressed. Aerosol
Copyright © 2003 Marcel Dekker, Inc.
product characteristics such as microbial challenge data, through-life testing of
units [26], resuspendability [27,28], first-shot assays, and typical loss of prime
should also be well known. The effect of spray assay methodology on the product
results is beneficial information. The product also should be fingerprinted for
three-dimensional plume patterns and particle size distribution by two or more
methods. One of the methods should evaluate the aerodynamic particle size. A
development history that describes chronological events during formulation is also
beneficial and frequently will help the specialist preparing the protocol. Reference
to the development report(s) may be included in the protocol document.
B. Preparation and Execution
The process validation protocol of a new aerosol product should be written by
a qualified manufacturing or validation specialist familiar with aerosols. Others
experienced in oral dosage forms such as suspensions or solutions would also
be helpful. These technical specialists may be within the research, validation, or
technical support departments, since this work will be done prior to approval of
a new product. Approval of the protocol should be given by quality assurance,
quality control, production management, and research.
Other experts will be involved in aerosols. A packaging specialist will
also play a critical role, since the functionality of the dosage form depends on
the package performance (i.e., valve and mouthpiece). Secondary packaging, in
which the filled unit may be check weighed, spray tested, and assembled with
the mouthpiece into a boxed unit, will need qualification and validation. In the
case of third-party or contract manufacturing, production and quality control
management at the manufacturing site should review the validation protocol and
report. In some instances, the third party may prepare a protocol; however, the
final responsibility for validation approval lies with the new drug application
(NDA) or abbreviated new drug application (ANDA) holder and marketer of
the aerosol.
The validation protocol should be prepared after the master batch record
is approved and signed by responsible parties (i.e., the manufacturer and NDA
or ANDA holder). The batch directions should be detailed and easily understood.
For example, mixing speeds and times, mixer positions, and method of
adding ingredients should be explained clearly. The protocol must agree in process
descriptions and flowcharts and be specific enough to remove any ambiguities
on process conditions, decisions, or product specifications. For these reasons,
it is usually beneficial to prepare a production-sized, prevalidation batch
with the proposed final batch record. This batch should also be completely
tested and meet finished product specifications.
The manufacturing or validation specialist should execute the protocol;
that is, that person should carry out and coordinate any process monitoring,
Copyright © 2003 Marcel Dekker, Inc.
aerosol line conditions, sample collection, and physical testing. The quality control
unit that will routinely analyze the product after routine production starts
should test the validation batches. This unit would also be responsible for stability
tests conducted on the validation batches.
C. Final Process and Product
The process must be validated at the manufacturing site(s) specified in the regulatory
filing (NDA or ANDA). The aerosol product must be prepared with the
manufacturing equipment and process intended for the routine production. It is
enticing the make the batch record changes during or after validation batches
have begun as a means of improvement. Changes in any manner, such as order
of addition of raw materials, method of weighing, screening of any raw materials,
aerosol line functional changes, mixing conditions, or mixing equipment,
should be considered as major changes and be documented accordingly. Revalidation
would be required for any changes made.
The batch record must be diligently followed during validation. Process
or formulation variations (quantitative or qualitative) are not permitted. A
change in any process step or steps will require restarting or amending the validation
program. Examples would be adding a dilution step for dissolving or dispersing
ingredients or changing homogenization times of wetting a suspension.
Because of time constraints it might also be tempting to begin validation
before the final setup is in place. An example might be to use a temporary filter
setup, tank cover, agitator propeller, or other piece of equipment. A short-term
delay in the start of validation batches would be preferred until the equipment
and laboratory readiness is complete. Testing must include validated analytical
procedures using the mouthpiece intended for the marketed package.
D. Worst-Case Conditions
Meaningful process limits on conditions will need to be established if not done
previously during development. Operating outside the set limits may or may not
lead to failure of the process or product specifications [29]. Limits may also be
used to demonstrate that process conditions are under consistent control. Examples
may be the humidity range (e.g., 30–45%) in the manufacturing room,
mixer speed ranges (45 to 55 rpm), mixer position (angle or distances), nitrogen
flow to a tank (2 to 4 standard cubic feet/hour [scfh]), or suspension temperature
range (20–30°F).
Evaluating worst-case conditions will justify many of these process limits.
A “subprotocol” for testing the worst-case scenario should be clearly specified
in the validation protocol. An alternative and preferable procedure would be to
test these conditions during development. For example, drug uniformity might
Copyright © 2003 Marcel Dekker, Inc.
be verified by using the lowest mixer speed (45 rpm), lowest temperature
(20°F), and highest nitrogen flow rate (4 scfh). Lack of volatility may be confirmed
by testing the highest nitrogen flow (4 scfh) at a high mixing speed (55
rpm). Rates of addition of raw materials (1 to 5 min) may also need evaluation.
These tests may be conducted during the prevalidation batch in order not to
interfere with a supposed production (validation) batch.
E. Timing
The protocol must be approved and signed before the first production batches
are started. Since aerosol manufacturing involves more package components
(valves, cans, mouthpieces) than other dosage forms, receipt and release testing
of these components must be incorporated in the planning schedule. Also, since
aerosol products involve more lengthy finished-product tests than other dosage
forms, release testing usually requires more analytical laboratory time.
F. Testing and Specifications
Due to extensive testing for aerosol products, the sampling and testing scheme
must be carefully reviewed before starting validation. Most MDI aerosols are
suspensions involving volatile propellants that are mixed and filled over long
periods (greater than 6 hr). Many drug uniformity samples may thus be required
to demonstrate reproducibility and show that volatility or loss of propellants and
drug is under control. Some aerosol tests that frequently should be monitored
are filled-unit yields, leakage rates, valve-spray reject rates, moisture values,
assays, and valve rubber leachables. Alert limits for critical tests are suggested
to avoid uncertainty over pass/fail situations and act as a guide when there is a
cause of concern. Tentative limits could be used until a history of production
batches is obtained. Examples may be a content uniformity RSD of 5.0% versus
specification of 6.0%. Developmental data on the pilot-scale batches will assist
in setting initial alert limits. These alert limits do not substitute for the actual
limits but merely serve as a guide for investigation.
G. Stability
Stability testing of the validation batches should be conducted at the quality
control laboratory. At a minimum it should be conducted at labeled storage
conditions. Accelerated conditions are not usually required because this is supplemental
stability, not primary.
Copyright © 2003 Marcel Dekker, Inc.
H. Protocol Format
1. The objective briefly describes the purpose of the validation program.
An additional objective is to provide supplemental manufacturing information
beyond that recorded in the batch documents.
2. The scope section describes what the process validation protocol covers,
the number of batches, and what it does not cover. In this part,
usually packaging validation or mouthpiece testing is included or excluded.
Any worst-case tests may be briefly described. Stability commitments
and stability protocols should be mentioned.
3. Formulation and components. The specific quantitative formulation
and components should be listed, along with identification or company
code numbers. The amounts per can, per batch, and percentages
should be listed here. Additional formulation information also may be
enumerated; including the following:
a. Amounts per actuation: drug formulated (µg drug and mg total),
drug delivered from mouthpiece, and drug retained on mouthpiece.
b. Amounts per can: sprayable contents (number of labeles sprays ?
mg/spray), nonsprayable contents (tail-off sprays, vapor retained,
drug retained), leakage over expiration period, spray-testing loss,
fill-weight allowance (underfill tolerance), material balance.
4. Process flowcharts. A flow diagram should indicate the process
steps and addition of raw materials. If possible, major equipment and
special environmental conditions may be included in the flowchart.
In-process tests may also be included. A second flowchart for activities,
raw material suppliers, shipments, and testing would also assist
in the overall picture of the aerosol manufacturing scheme, especially
for multiple site or third-party activities. An example of a process
flowchart for a fictitious suspension product (2160.4-kg batch size for
100,000 units) is shown in Figure 6.
5. Document checklist. All documents that should be examined and in
proper order prior to the initiation of the validation batches are listed.
They are checked for availability and accuracy. Preparation of batches
should not commence unless these documents are finalized and
signed. An example is shown below:
a. New drug application (applicable sections, NDA or ANDA)
b. Calibrations: scales and balances, temperature-measuring devices,
tachometers, environmental conditions measurements (room temperature,
humidity, pressure; HEPA filter certification), pressure
gauge.
c. Standard operating procedures: physical tests (pressure testing,
Copyright © 2003 Marcel Dekker, Inc.
Figure 6 Process flowchart.
Copyright © 2003 Marcel Dekker, Inc.
spray dosage, number of sprays, moisture in unit, weight loss,
testing of valves, cans, actuators, overcaps), chemical tests [inprocess
assay, identification test, drug assay (mg per can), drug
valve testing].
d. Product specification sheet (line check form, bill of materials).
e. Training documentation.
f. Cleaning procedures (cleaning procedures, cleaning validation report).
g. Certificates of analysis of components (for each validation batch):
each raw material (active, flavors, cosolvents, surfactants, antioxidants,
antimicrobials), propellants (CFCs), nitrogen or other inert
gases, metered valves, canisters, overcaps, mouthpieces.
h. Master batch record documents: batch card, chemical weighing
records, yield reconciliations sheets, in-process data sheets, production
area readiness checklist, computer system documentation,
mechanical line setup sheets.
i. Qualification reports and equipment manuals: tank or vessels,
mixers [homogenizer (colloid mills), tank agitator, mixers], concentrate
filler, recirculation pumps, crimper, pressure filler, checkweigher,
spray-testing unit, environmental control areas (temperature
and humidity).
j. Development report (research report number).
k. Safety documents (material safety data sheets).
l. Validation protocol (current document).
6. Process monitoring. This section depicts the intended process conditions
and parameters that will be measured. Items that are not recorded
in the batch record but that may be critical should be tabulated
here, along with target or expected values. The frequency of the measurement
(e.g., once), the method (e.g., timer), and where it will be
recorded (e.g., form A) should be tabulated. Many of these items will
depend on past experience during development. An example may be
the rate of addition and location of the micronized active ingredient
or observations of the aerosol solution or suspension appearance. In
short, if a quantitative measure of a given step is obtainable, this
number should be recorded. A thorough and detailed master batch
record will minimize the additional monitoring required for validation.
Filling line items on a line setup sheet will also need monitoring.
Items not recorded in batch documentation should be tabulated or
listed in the protocol as intended for monitoring during validation.
Examples might be crimping collect numbers, line speeds, or propellant
injection pressures during the filling process.
7. Sampling and testing. This section provide specifics on the sam-
Copyright © 2003 Marcel Dekker, Inc.
pling, testing, and acceptance criteria intended during the validation
batches. Methods of sampling concentrate or removing filled cans
from the line should be clearly described. Lists of in-process tests,
where sampled, number of cans, and responsibility should be tabulated.
A separate table may be needed to describe the test, method,
frequency, specifications, and comments. All in-process samples must
pass specifications in order to claim a validated process. Statistical
testing at the beginning, middle, and end of the process usually can
demonstrate the consistency of manufacturing. Similarly, tables of
finished product tests showing expanded testing regimens (e.g., beginning,
middle, end, and composite), methods, and specifications will
be needed.
8. Responsibility and timing. This section will provide a guide for specific
goals of each group. The target timing requirements (e.g., 6
weeks to place on stability) will show the responsibility of each person(
s) from protocol writing to report approval.
9. Appendix. Forms with blanks may be provided in the protocol to be
filled out during each validation batch. These forms are for process
monitoring of compounding, line functions, in-process sampling, and
so on. They should include such specifics as types of measuring
devices (serial numbers) and include sign-offs for “done by” and
“checked by” signatures. A clearer indication of the process requirements
results from preparing and reviewing these forms.
V. ADDITIONAL VALIDATION PROTOCOL ITEMS
Additional items that were not detailed in the aforementioned protocol description
may be monitored during validation.
A. Materials Monitoring
Metered valves are critical to the functionality of this dosage form, and a thorough
understanding of this component is essential. Table 3 shows some tests
conducted on metered valves. Footnoted items are special tests performed for
valve characterization, not necessarily for individual lot release.
Storage and handling of the propellants (CFCs and HFAs), types of filters,
transfer piping, and storage tanks should be standardized. Any observations of
the appearance of the propellants should be recorded. The supplier’s specifications
should be reviewed.
Other ingredients and packaging components might require special environmental
storage conditions. Room temperature and humidity should be docu-
Copyright © 2003 Marcel Dekker, Inc.
mented during facilities qualification prior to process validation (e.g., bulk drug,
surfactants, cosolvents, and flavors).
Containers for storing the raw materials should be specified in the material
specifications sheets or packaging bill of materials. Although outside the scope
of validation, the manufacturing specialist should be aware of such issues.
Weighing of ingredients by the weighing or chemical dispensing department
should include the gross, tare, and net of each ingredient. Future abnormalities
of yielding or potency may be found by having unusual tares or discrepancies
arising from the weighing of components. Unusual tares such as for jacketed
tanks should include specifics (coolant, lid, etc.) and the method of taring.
B. Process Monitoring
1. Preparation of Suspension or Solution
Validation should confirm the order of addition of raw materials, rate of addition,
method of addition, and mixing conditions during compounding of the
aerosol suspension or solution. The specific type(s) of mixer(s), blade(s),
speed(s) and position (pitch), or placement in the vessel should be specified
in the batch directions. The batch temperature and room conditions (temperature,
humidity) should be fully documented if not recorded in the batch directions.
Air Cleanliness. Air cleanliness may be an important factor, especially
if the compounding is done in open vessels exposed to the ambient air. Air
cleanliness (type of air) by recording high-efficiency particulate air (HEPA)
filter types, airborne particulate counts, and any microbial monitoring such as
sampling and incubating with media may be part of the environmental testing
plan. Air pressures and cleanliness testing, although good measures of
conditions, are not required for other oral products. A qualification or facilities
testing program is usually beyond the scope of the specific process validation
program.
Purging. Prior to compounding of batch ingredients, preparatory steps
should be monitored. Any purging of tanks, lines, and so on with dry gas should
be recorded for any filtration, flow rates, and position of gas lines. For many
products it is desirable to purge the drug concentrate tank prior to and during
batch preparation with an inert gas such as nitrogen. This serves to remove
undesirable moisture and oxygen in the tank head space. The type of gas and
any treatment such as drying agents or filtration should be verified during validation.
Frequently stainless steel piping or tees into tank covers are employed
to introduce dry nitrogen NF into the tank. The source and grade (e.g., high
purity nitrogen) should be documented, along with details of the method and
position of purging the tanks.
Copyright © 2003 Marcel Dekker, Inc.
Recirculation. Recirculation of drug concentrate may be used during the
filling operation to maintain a sufficient source to the filling device. Concentrate
may be pumped between the drug suspension or solution tank to the filling
system, and then the excess is returned to the tank. The type, model, and serial
number of pumping equipment and flow rates must be monitored. The time
recirculation is started and stopped should be known. If alternative mechanisms
such as a level controller (float valves) are used the settings should also be
documented. In some instances a filter may be used for solution or suspensions.
Similar to filtration of propellant, a challenge test of the filter with small particles
may be conducted to demonstrate adequate retention. This would be described
in a separate testing protocol, preferably during the development.
Residual Losses and Yields. The yield of the concentrate, filling, and
any residual tank or pumping loss is an important measure of how the process
behaved. Accounting for drug suspension and solution should be complete and
rigorously done. An investigation of losses should be made when these losses
exceed unusual amounts (about 5–7%) of the drug suspension or solution. Tentative
specifications of the yield should be considered after the validation
batches and reviewed after several more production batches are made.
2. Aerosol Line Functions
The amount and type of purge at the can vacuum station (can cleaning) should
be known. The pressure and amount of vacuum applied to the empty can should
also be measured. A challenge test may be done in which particulates are intentionally
placed into empty cans to observe visually the removal of the foreign
contaminants. As for a filtration challenge, a brief protocol should be written if
this is elected. While filling the cans with appropriate drug solution or suspension,
any items not written in the batch directions, line setup, or other batch
records should be reported during validation. For example, any special nitrogen
shroud assembling for environmental control or other devices for filling accuracy
should be known.
In addition, during validation an entire group of cans may be isolated for
each filling nozzle in between check weighing intervals. For example if every
500th is manually check weighed, then a group of 500 cans should be separated
and passed individually through the check weigher to verify the in-between
values. Also, the filling variation, such as standard deviation, should be calculated
for each filling nozzle or piston. Relative standard deviations of less than
3% are considered acceptable, although values of less than 1.5% should be a
goal. The type and amount of gas purged into the canister will be verified during
validation. The location at which this is done on the line is recorded, and the
time and after purging is known. The flow rate of the gas into the can as well
as the position inside the can is also known.
Copyright © 2003 Marcel Dekker, Inc.
The method of valve placement after filling and equipment specifics must
be documented.
Crimping. Since crimping is delicate and complicated, this step will
require more attention than others [23]. The specific equipment, such as
collet numbers, settings of pads, or downward head pressures, must be known.
The details should be clearly spelled out in product setup documents, especially
if different personnel are used among the validation batches. Several
measurements are used to evaluate the valve crimp. Specifications for these
measurements should be set, along with acceptable leakage or weight loss data
justifying these crimps and their measurements. Valve delivery such as that
measured by spray weights should also be recorded to verify that the operation
of the valve is not affected by the crimping step. During validation
batches, crimp measurements should be taken at specified intervals to ensure
an acceptable and reproducible process step. Statistical sampling would be
best, such as samples taken hourly during the duration of the batch. Alternatively,
groups of 12 cans at the beginning, middle, and end of the batch
may be done. This will ensure statistical equivalence throughout the batch.
Pressure settings on the crimping equipment are to remain unchanged. Any
change in settings will necessitate resampling and retesting to verify the new
settings.
Propellant Filling. Propellant filling must likewise specify the setup and
any important quantitative values of this process step. Pressure testing verifies that
the proper propellant is utilized. The type of equipment, (e.g., cylinder and piston
type, size, injection head nozzle, O-ring specifics, and special features) should be
well known as for concentrate filling. Settings of downward pressure and injection
pressure must conform. The propellant filling step should be individually validated,
as is done for the concentrate filling. Control charts for propellant fill weights
should be included in the validation batches. These will verify that specifications
are met and adequate control limits have been determined. The process capability
may also be determined from the individual weights.
Check Weighing. Check weighing of all cans after the unit is crimped
and filled must not be neglected. The type and orientation of cans, ranges set,
speed of check weighing, and an appropriate challenge of the accuracy of the
check weigher must be monitored. The type and line position of the check
weigher need to be verified. The weight ranges, zones, and can feed rate should
be written. The number of rejects (high and low) should be part of the batch
reconciliation documentation. After validation, a good grasp of the usual allowable
rejects will be available. Any inconsistencies should be traced to the specific
filler. The weight rejects may also be individually weighed on a sensitive
balance to confirm the accuracy of the check weigher. Cans for setting the check
Copyright © 2003 Marcel Dekker, Inc.
weigher with heavy and light filled units are frequently used, as well as empty
units for taring.
Leak Testing. Leak testing, like check weighing, will have its specified
conditions that do not affect the product but similarly allow for inspection of
faulty units. The temperature for the can and the duration must be described in
the batch directions and confirmed during validation. Sometimes one may wish
to know the temperature the product reaches. Thermocouples or temperature
indicators may be used to assess this. All cans are leak tested to cull out any
faulty units that may leak in the field. For example, submersion at 120°F for 3
min may be adopted, since the contents may approach that temperature after
that time. The labeling and regulatory requirements (department of transportation)
may best be applied here. A desired temperature should have a temperature
range and time range. It must also be verified that this step does not alter the
quality and stability of the dosage form. Immediately after the test, the units
may remain warm for a given period of time. The cans should not be further
processed (spray testing), but should be allowed to cool to room temperature.
Frequently, for small MDI units, 1/2 to 1 hr is usually sufficient.
3. Other Line Functions
Storage of the aerosol product after filling must be described in the batch records.
Sometimes the cans are stored valve down (for seating the valve gaskets)
or valve up to minimize exposure to leachables in the rubber componentry. The
shipper description should be in the bill of materials packet. Spray testing is a
critical step to prevent continuous or no-fire units from reaching the customer.
All units are tested during the filling operation or during the packaging operation.
Process monitoring may encompass verifying the proper number of valve
depressions for testing, challenging the method with intentionally faulty units,
and establishing the normal expected reject rate for a given valve in the validated
process. The number of depressions of the valve is more descriptive than
the number of sprays. The first valve depression of a new unit is frequently a
prime, nonspraying shot. The actuator used should be specified in the batch
records. If a manual inspection system is utilized, proper training of operators
must be conducted. Actuators should be used only for a given period of time
before being replaced with new ones. A history of the particular valve’s defects
and frequency should be known before validation of production-size batches
begin.
Other functions such as can coding (lot numbers, line designation) must
be considered a process step. Can coding is a means of identifying an unlabeled
unit by lot number or code. It is usually done with an ink-jet labeler or similar
device. Another coding system may differentiate between filling tracks (front,
back) within one lot. For example, if needed, the back track may be coded with
Copyright © 2003 Marcel Dekker, Inc.
a small black mark to differentiate it from the front tract. These code marks are
covered with the can label during that operation.
VI. VALIDATION REPORT
The validation report should contain the approved validation protocol, tabulated
or graphical results, process monitoring (forms), and all analytical results of the
validation batches. A copy of the batch records and raw material releases may
be in the appendix, although this usually adds considerably to the size of the
report. The presentation of data should be spread out over many pages and be
easily understood and neat. Small tables of process conditions or data should be
in one style that appears concise and is easily read. Stability data can be
amended at a later date if desired. Special investigations or additional tests or
retests may have to be explained in the report if deviations of any kind occurred.
The validation report should have a conclusion that explains the manufacturing
specialist’s (preparer’s) statement and opinion. Appendices may be used to explain
detailed equations (e.g., control chart statistics) or specific methods (e.g.,
spray delivery methods). Information that is included in the batch records may
not have to be repeated, but in some instances (e.g., crimp measurements) may
be beneficial for presentation. The use of figures or graphs is strongly suggested
because these plots may show some trends and insights from a large database.
Recommendations may also be made in the report, such as preparing more
batches, amending certain tests, expanding batch directions, or creating alert
limits.
The validation report should be approved prior to product distribution and
kept permanently on file in quality assurance. Furthermore, production should
not commence until the validation report is approved. The data in the report
should serve as a foundation for future troubleshooting; that is, they should be
specific enough, along with the batch directions, for the process to be easily
duplicated. Any equipment qualification reports, such as filling equipment,
crimper, check weigher, homogenizer, or propellant gasser, should likewise be
readily available if this is warranted. Stability testing on all validation batches
must be performed according to the protocol, according to the NDA/ANDA
stability plan.
The delivery of drugs to the respiratory system via an MDI has been the
dosage form of choice for over 50 years. Propelled with CFCs, they have had a
remarkable safety record and acceptance by both patient and physician. The
development, production, and marketing of this dosage form has resided in a
very limited number of pharmaceutical companies. With the phase-out of CFCs
and the introduction of the more environmentally acceptable HFA propellants,
a newer and different technology is emerging that affects all aspects of this
Copyright © 2003 Marcel Dekker, Inc.
exciting area. While the patient and physician acceptance of the HFA formulation
for MDIs has been less than expected (due to different taste, feels, cost,
etc.), and limitations on the formulations have been discouraged or limited by
several patents this never the less is the direction for the future and hopefully
technology will emerge to overcome these present-day shortcomings.
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Copyright © 2003 Marcel Dekker, Inc.
11
Process Validation of
Pharmaceutical Ingredients
Robert A. Nash
Stevens Institute of Technology, Hoboken, New Jersey, U.S.A.
This chapter reviews the requirements of the U.S. Food and Drug Administration
(FDA) for process validation of manufacturing pharmaceutical active ingredients
(APIs) and inactive ingredients used in human and veterinary drug
products.
The Food, Drug, and Cosmetic Act (FD&C Act) defines drug as (clause
A) articles recognized in the official U.S. Pharmacopeia, official Homeopathic
Pharmacopeia of the United States, official National Formulary, or any supplement
to any of them; (clause B) articles intended for use in the diagnosis, cure,
mitigation, treatment, or prevention of disease in man or other animals; (clause
C) articles (other than food) intended to affect the structure or any function of
the body of man or other animals; and (clause D) articles intended as a component
of any articles specified in clauses A, B, or C.
Based on the above definition, active ingredients, excipients, coloring
agents, flavors, and in-process materials are components of a drug and therefore
are subject to the same drug laws in the FD&C Act. One such law, Section
501(b), declares a drug to be adulterated if the method used in or the facilities
or controls used for its manufacture, processing, packing, or holding do not
conform to or are not operated or administered in conformity with current good
manufacturing practice (CGMP) to assure that the drug meets the requirements
of this act as to the safety, has the identity and strength, and meets the quality
and purity characteristics that it purports or is represented to possess.
The FDA publicly committed to develop a CGMP regulation for bulk
Copyright © 2003 Marcel Dekker, Inc.
drugs on September 29, 1978, when the 1978 amendments to the CGMP regulations
(Title 21 of the Code of Federal Regulations, Parts 210 and 211) were
published in the Federal Register. Page 45050 of the preamble to this final rule
stated that the CGMP regulations “apply to finished dosage form drugs (under
§§ 210.3(b)(4) and 211.1) and are not binding requirements for chemical manufacturing.”
It further explained that the CGMP regulations for finished pharmaceuticals
“can serve as useful guidelines in the manufacture of chemicals,” and
specified “The agency plans to develop specific CGMP regulations on production
of bulk drugs.”
In its guideline to inspection the FDA set the following criteria to identify
an industrial chemical as a bulk pharmaceutical chemical (BPC) (FDA, 1991):
When there is no recognized nondrug commercial use for the chemical
When it reaches the point in its isolation and purification at which it is
intended that the substance will be used in a drug product
When the manufacturer sells the product or offers it for sale to a pharmaceutical
firm for use in a drug product
Active and excipient chemical ingredients used in drug products may
therefore be considered as BPCs. These materials can be made by chemical
synthesis, fermentation, enzymatic reactions, recombinant DNA, recovery from
natural materials, or a combination of the above.
In the mid-1990s the term active pharmaceutical ingredient (API) was
introduced by the FDA to replace the term bulk pharmaceutical chemical (BPC).
Excipients are used in drug substance formulations to provide an acceptable
drug product. The FDA considers excipients as BPCs, but has not issued
specific GMP regulations for them. The International Pharmaceutical Excipient
Council (IPEC), however, issued a proposed GMP for excipients in 1995 and a
guide, “Significant Change for Bulk Pharmaceutical Excipients” BPEs, in the
year 2000.
Active pharmaceutical ingredients are most often manufactured in batch
or semicontinuous process since most APIs are potent and normally used in
relatively small amounts in each batch of drug product, especially during the
early phase of drug product introduction. With the advent of many new APIs,
the capital investment for continuous operation is not economically feasible. In
a batch process, the product is often made from a well-identified, approved raw
material supply, which is usually present at the start of the reaction.
Most drug product manufacturers use the same excipients, and usually
in relatively high concentrations in the drug product when compared to the
concentration of the API. The manufacture of excipients therefore often involves
continuous processing. A continuous process is one in which material (both raw
and/or in-process) is added continually as the finished product is removed for
Copyright © 2003 Marcel Dekker, Inc.
further processing or is collected for packaging. A continuous process may involve
manufacture in a continuous reactor, in which unique identification or
traceability of raw materials is not feasible. Continuous processing can involve
a batch reaction, in which the identification of the reactants is clearly known
but in which further processing, such as purification or drying, may be done in
a continuous fashion. The excipients are often manufactured on a scale sufficiently
large to justify continuous processing, often because of their other nonpharmaceutical
applications; for example, at a rate of 100,000 kg/shift, where
only 10% is allocated to the pharmaceutical industry and the rest for commercial
purposes. One of the main drawbacks of continuous processing is that the quality
of a material produced by such a process in terms of the uniformity of both
the impurity profile and physical properties is more difficult to accomplish when
compared to material produced by batch processing.
The FDA believes that the general principles of validation apply to any
process and that these principles don’t change from process to process. The
specific type of validation or degree of validation differ for API processes when
compared to those required for drug products. In the production of dosage
forms, all manufacturing steps (unit operations) in the production of the final
product, such as cleaning, weighing, measuring, mixing, blending, packaging,
and labeling, are encompassed by process validation.
For API processes, the FDA does not expect validation of all manufacturing
steps, but accepts validation of critical process steps. Section XI.A of the
March 1998 draft API guidance document states, “Validation should embrace
steps in the processing of APIs that are critical to the quality and purity of the
final API.” The FDA, however, does not specify what it considers critical, but
wants the manufacturer to determine the critical process steps and critical process
parameters. For new chemical entities, data used to identify critical processing
steps and critical parameters would be derived from research or pilot scale
batches. For established API processes this information could be obtained from
previously manufactured production scale batches.
According to Rivera Martinez, critical steps are not limited to the final
API stage and can include intermediate steps that introduce an essential molecular
structural element, result in a major chemical transformation, introduce significant
impurities, or remove significant impurities.
Critical process steps are usually determined by analyzing process parameters
(factors in a process that are controllable and measurable) and their respective
outcomes. Not all process parameters affect the quality and purity of APIs;
namely its impurity profile and physical characteristics. For validation purposes,
manufacturers should identify, control, and monitor critical process parameters
that may influence the critical quality attributes of the API. Process parameters
unrelated to quality, such as variables controlled to minimize energy consumption
or equipment use, need not be included in process validation.
Copyright © 2003 Marcel Dekker, Inc.
An approach to identify critical process parameters involves conducting
“critical step analysis” in which API manufacturers challenge the unit operations
(e.g., reaction step, crystallization, and centrifugation) during the process qualification
stage to determine those critical process variables that may affect overall
process performance. Process validation should confirm that the impurity
profile for each API is within the limits specified. The impurity profile should
be comparable to or better than historic data, the profile determined during
process development or batches used for pivotal clinical, and toxicological
studies.
I. IMPURITY PROFILE
The FDA guidance document on impurities in drug substances recommends
that individual impurities greater than 0.1% should be fully characterized and
quantified by a validated analytical method. In addition, the USP permits up to
2%of ordinary nontoxic impurities in APIs. Such impurities may include: residual
starting materials, intermediates, reagents, by-products, degradation products,
catalysts, heavy metals, electrolytes, filtering aids, and residual solvents.
Known toxic impurities, however, should be held to a tighter standard
(below 0.1%). One of the objectives of a successful validation program for APIs
is to maintain control over the impurity profile and to hold contaminants and
impurities to an achievable minimum standard.
For each batch of API produced, the following information should be
supplied in the batch completion report:
Batch identity and size
Date of manufacture
Site of manufacture
Specifics of the manufacturing process
Impurity content (individual and total)
Reference to analytical procedures used
Disposition of the batch
In summary, the drug substance acceptance criteria should include information
with respect to organic impurities, residual solvents, and inorganic impurities.
Similar standards should also be applicable to pharmaceutical excipients.
Figure 1 shows the use of a single analytical method function as an important
technical bridge between the API and the drug product as they move through
the various stages of development, clinical study, process development, and process
validation into production.
Copyright © 2003 Marcel Dekker, Inc.
Figure 1 Working in parallel. (Courtesy of Austin Chemical Co., Inc.)
II. ACTIVE PHARMACEUTICAL INGREDIENT
Presently the overwhelming number of APIs are organic, carbon-based, chemotherapeutic
agents prepared by either chemical synthesis or fermentation techniques
or are isolated from natural products. More than 90% of the active drug
Copyright © 2003 Marcel Dekker, Inc.
substances are solids, the majority of which are white and crystalline, and with
a well-defined melting point or range. The rest are liquids at room temperature,
while a few are medicinal gases.
The organic chemical structures of most active drug substances are composed
of carbon, hydrogen, oxygen, and nitrogen atoms and may contain an
occasional sulfur, phosphorus, or halogen (fluorine, chlorine, bromine, and iodine)
in the specific chemical configuration. The molecular weights of most
APIs range from 100 to 1000 but tend to be about 300 daltons. Melting points
range between 100 and about 300°C.
Active pharmaceutical ingredients belong essentially to one of the following
four basic chemical classes:
1. Weak acids and their salts (sodium sulfacetamide, potassium guaiacolsulfonate,
calcium fenoprofen, magnesium salicylate, etc.) approximately
30%
2. Weak bases and their salts (nortriptyline hydrochloride, phenelzine
sulfate, chloroquine phosphate, scopolamine hydrobromide, tamoxifen
citrate, etc.) approximately 45%
3. Organic nonelectrolytes (neutral molecules, chloral hydrate, hydrocortisone,
testosterone, mannitol, etc.) approximately 15%
4. Quaternary compounds (substituted ammonium salts, methacholine
chloride, mepenzolate bromide, phospholine iodide, etc.) approximately
10%
Weak acids and weak bases and their salts account for about 75% of the
APIs currently used in drug products.
Prodrugs are drug substances that are biotransformed in the body to active
metabolites and chemotherapeutic agents. Examples include sulfasalazine to sulfapyridine,
phenylbutazone to oxy-phenbutazone, aspirin to salicylate, and hetacillin
to ampicillin. In some cases, such as aspirin (ester) and hetacillin (amide),
hydrolysis in water releases the active drug moiety contained within the basic
structure of the prodrug.
The FDA often considers such simple, uncomplicated amides, lactams,
esters, and lactones as derivatives of the active drug substance in the same way
as it treats salts (electrolytes) and ion-pair complexes (nonelectrolytes) of the
same basic chemical structure.
The FDA principle “You are what you claim you are” applies to APIs as
well as to foods, drugs, and cosmetics.
Take, for example, dextrose. When dextrose is used as a sweetener in
baked goods, it is a food ingredient and subject to the requirements of food
products. When dextrose is used as a sweetener or diluent in tablet, capsule, or
liquid preparations, it is an excipient. When it is used in the manufacture of
sterile dextrose injection, it is an active drug substance and an API but now
Copyright © 2003 Marcel Dekker, Inc.
subject to assay and testing for bacterial endotoxins and 5-hydroxymethyl furfural
content.
Pharmaceutical excipients (inactive ingredients) are substances other than
the active drug substance or the drug product that have been evaluated for safety
and are included in the pharmaceutical dosage form (drug delivery system) for
one or more of the following functions:
1. Aid in the processing of the drug product during manufacture (e.g.,
binder, disintegrant, lubricant, suspending agent, filtering aid)
2. Protect, support, or enhance stability, bioavailability, or patient acceptability
(e.g., chelant, surfactant, sweetener)
3. Assist in product identification (e.g., colorant, flavor, film former)
4. Enhance any other attribute of the overall safety and effectiveness of
the drug during storage or use (e.g., inert gas, preservative, sunscreen)
Like APIs, pharmaceutical excipients are made by chemical synthesis,
fermentation, recovery from natural materials, and so on. Often purification procedures
may not be employed in the manufacture of such pharmaceutical excipients
as clays, celluloses, starches, and natural gums. In addition, the physical
and chemical change of certain excipients during processing is not uncommon.
Unlike APIs, many excipients have complicated chemical and physical structures
that do not yield easily to modern analytical and chromatographic methods.
More than 200 monographs of pharmaceutical excipients appear in the
third edition of the Handbook of Pharmaceutical Excipients, published jointly
by the American Pharmaceutical Association and the Pharmaceutical Press in
the year 2000. In addition, more than 200 of the same pharmaceutical ingredients
(excipients) are listed in NF 19 and cover more than 40 different excipient
categories, from acidulants to wetting agents. It has been estimated that there
are more than 1000 different pharmaceutical excipients in use worldwide at the
present time.
The International Pharmaceutical Excipient Council in the United States
(Arlington, Virginia; 703-521-3338) has issued a GMP guideline for excipient
bulk pharmaceutical chemicals. In conjunction with both the European and Japanese
Pharmaceutical Excipient Councils, the council is currently engaged in
establishing international harmonization excipient monographs for the more
popular pharmaceutical excipients. A list of important and popular pharmaceutical
excipients is given in Table 1.
Basic information with respect to GMPs for APIs is covered in the following
recently issued technical guidance documents:
“PhRMA Guideline for the Production, Packing, Repacking or Holding of
Drug Substances (APIs).” Pharmaceutical Technology (Dec. 1995/Jan.
1996).
Copyright © 2003 Marcel Dekker, Inc.
Table 1 Fifty Most Commonly Used Excipients in Drug Products
Pharmaceutical excipient Function Pharmaceutical excipient Function
Acesulfame potassium Sweetener Kaolin Drying agent
Alcohol Solvent Lactic acid Acidifier
Alginic acid Suspending agent Lactose Diluent and filler
Benzalkonium chloride Preservative Magnesium stearate Tablet lubricant
Benzyl alcohol Preservative Methyl paraben Preservative
Bentonite Suspending agent Microcrystalline cellulose Tablet binder
Carbomer Tablet binder Mineral oil Solvent
Carboxymethylcellulose sodium Suspending agent Petrolatum Vehicle
Carrageenin Suspending agent Pregelatinized starch Tablet disintegrant
Cellulose acetate phthalate Coating agent Polyethylene glycol 400, 3350 Vehicle
Citric acid Acidifier Polyoxyethylene alkyl esters Surfactant
Colloidal silicon dioxide Tablet glidant Polysorbate 80 Surfactant
Croscarmellose sodium Tablet disintegrant Shellac Coating agent
Crospovidone Tablet disintegrant Sodium chloride Osmotic agent
Dibasic calcium phosphate Tablet binder Sodium hydroxide Alkaline agent
Disodium edetate Chelating agent Sodium saccharin Sweetening agent
Docusate sodium Surfactant Sodium starch glycolate Tablet disintegrant
Ethyl cellulose Coating agent Starch (corn, wheat, potato, rice) Tablet filler
Gelatin Coating agent Stearic acid Tablet lubricant
Glycerin Solvent Stearyl alcohol Viscosity agent
Hydrochloric acid Acidifier Sucrose Sweetener
Hydroxyethyl cellulose Coating agent Talc Glidant
Hydroxypropyl cellulose Coating agent Triacetin Solvent
Hydroxypropyl methylcellulose Coating agent Titanium dioxide Opacifier
Isopropyl alcohol Solvent Xanthan gum Suspending agent
Source: Data supplied by the International Pharmaceutical Excipient Council.
Copyright © 2003 Marcel Dekker, Inc.
European Chemical Industry Council/European Federation of Pharmaceutical
Industries Association. GMP Guide (Aug. 1996).
FDA’s manufacturing, processing, or holding APIs draft guidance, issued
March 1998.
The Pharmaceutical Inspection Convention API guide (revised April 1998).
International Conference on Harmonisation (ICH). GMP Guide for APIs
(Nov. 2000).
GMP guide for APIs issued by the World Health Organization (WHO) in
July 2001 (also reflects ICH guidance documentation).
In addition, specialized guidance information has also been issued for the
following topics:
ICH. Guidance for Industry: Q1B Photostability Testing of New Drug
Substances and Products (Nov. 1996).
FDA. Guidance for Industry, ANDAs: Impurities in Drug Substances (June
1998).
FDA. Guidance for Industry, BACPAC I: Intermediates in Drug Substance
Synthesis (Feb. 2001).
Guidance documents do not have the same weight and standing as such
regulations as 21 CFR 211 (cGMPs), but they do reflect the best thinking of the
regulatory authority with or without the formal support of the industry covered
by the guidance information. If a particular company can provide solid scientific
support for the approach the company is taking, which may differ from the
information provided in the guidance document, in most situations it should be
acceptable to the regulatory agency.
The ICH guidance document covers the following essential topics:
Introduction (object and scope)
Quality management (internal audits and reviews)
Personnel (qualifications, hygiene, and consultants)
Building and facilities (design, construction, water, containment, lighting,
sewage, and sanitation)
Process equipment (design, construction, maintenance, cleaning, calibration,
and computerized systems)
Documentation and records (systems, specifications, raw materials, intermediates,
labeling, packaging materials, master production and batch
records, laboratory control records, batch production record review)
Materials management (receipt, quarantine, sampling, testing, storage, and
re-evaluation)
Production and in-process controls (unit operations, time limits, in-process
sampling, blending of intermediates or APIs, contamination control)
Packaging and identification of APIs and intermediates
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Storage and distribution (warehousing and distribution)
Laboratory controls (testing of intermediates and APIs, validation of analytical
procedures, certificates of analysis, stability monitoring of APIs
expiry dating, retention samples)
Validation (policy, documentation, qualifications, approaches to process
validation, periodic review of validated systems, cleaning validation,
and analytical methods validation)
Change control
Complaints and recalls
Contract manufacturers and laboratories
Agents, distributors, repackers, and relabelers
Specific guidance for API manufacture by cell culture or fermentation
APIs for use in clinical trials (quality, equipment, facilities, control of raw
materials, production, validation, change control, laboratory controls,
and documentation)
In most synthetic chemical reactions, the processes involved have been
simplified. (See Fig. 2.) Process validation should be conducted for the final
active drug moiety or API (A), the final intermediates (B and C), as well as the
key intermediates (D and E) that produced B and the key intermediates (F and
G) that produced C. Final product (A) and final intermediates (B and C) should
Figure 2 Pathway to API process validation.
Copyright © 2003 Marcel Dekker, Inc.
be subjected to major in-process testing for identity, strength, potency, and purity,
while key intermediates (D, E, F, and G) should be held to somewhat less
intensive in-process testing for identity, strength, potency, and purity.
If earlier intermediates in the chain are also produced in the same plant,
they should not be held to the same rigorous chemical, physical, and microbiological
standards that were used to produce the key intermediates, final intermediates,
and final active moiety or API. Nevertheless, it would not be appropriate
to have a plant produce both CGMP-compliant and non-CGMP-compliant materials
without some reasonable GMP-type procedures and reasonable testing standards
established for non-CGMP-compliant materials. Higher standards can be
imposed on an outside manufacture or vendor of APIs if they are interested in
obtaining your business at a reasonable price. In any event the emphasis will be
placed upon your own quality control and quality assurance functions to make
sure that the outsource company consistently produces product that meets the
agreed-upon standards placed by your company on their materials.
Diagrams for a synthetic chemical, single reaction step process (Fig. 3)
and a typical single product fermentation (Fig. 4) are taken from Wintner’s
excellent article [“Environmental Controls in the Pharm. Industry. Pharm Eng
(April 1993)]. Both flow diagrams feature about the same number of unit operations
and start with raw material weighing procedures. The essential difference
between the two figures is that the fermentation process features sterilization,
inactivation, and preservation unit operations.
The critical unit operations that should be monitored and/or optimized are
the reaction and fermentation steps for the purpose of increasing API yield and
reducing the residual impurity profile. Other critical unit operations that are
especially important to the end user (pharmaceutical dosage form operations)
include precipitation or crystallization, milling, sizing, and purification operations,
which may affect the physical properties (particle size and shape, bulk
powder flow, blend uniformity, and compressibility) of the API.
Theoretically, every unit operation conducted in the plant comes under the
CGMP umbrella, and is therefore subject to the need for validation documentation
requirements. This includes not only the final API but also the manufacture
of the final intermediate(s) (or main reactants), key intermediates that are used
to prepare the final intermediate(s), all the way back to commercial starting
materials that enter the plant, as well as the pivotal intermediates thereafter.
The level of control and validation documentation required (i.e., through
increased testing and tighter specifications) increases as one moves closer, in a
multistep, in-plant process, to the outcomes [i.e., final intermediate(s) and the
API itself]. Naturally, when key and final intermediates are sourced from outside
the company, they must enter with appropriate certificates of analysis
(CofA), plus thorough inspections of off-site facilities by quality assurance personnel.
Copyright © 2003 Marcel Dekker, Inc.
Figure 3 API process. (Pharm Eng 13(4), 1993.)
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Figure 4 Typical fermentation API process. (Pharm Eng 13(4), 1993.)
Copyright © 2003 Marcel Dekker, Inc.
Table2 Important Parameters to be Evaluated in the Reaction Step
Parameter Outcome
Temperature Yield and purity
Time Yield and purity
Oxygen pressure Yield and purity
CO2 pressure Yield and purity
Medium or solvents used Yield and purity
Type, purity, and amount of catalyst used Yield and purity
Type and speed of agitators Particle size distribution
Reagent ratios Particle shape and stereospecificity
Reagent purity Catalyst performance
Reagent order and addition rate Yield, purity, and morphology
Those unit operations, especially the reaction step(s) that are considered
critical, are determined through the analysis of process variables or their respective
measured responses or outcomes (Table 2). The most favorable operating
conditions to run the reaction are usually worked out in the laboratory (1X
stage) and refined and/or optimized in the pilot plant (usually at the 10X stage).
III. API PREFORMULATION STUDIES
In order to develop a robust formula for a drug product (pharmaceutical dosage
form) it is important to understand the chemical and physical properties of the
API in conjunction with excipients that may be used to create the most stable
product formula in terms of activity and potency. An outline of possible preformulation
studies that should be conducted to ensure a proper and complete
understanding of the chemical and physical properties of the API is presented
in Table 3.
In addition, simple binary studies with key excipients should be done to
establish physical and chemical compatibility between the API and the selected
excipient. These studies need not be elaborate, but will provide useful information
to the formulator during the critical drug product development stage.
IV. THE VALIDATION OF APIs
According to the FDA’s Guidelines on General Principles of Process Validation,
the term process validation, whether for APIs or drug products, is defined
as “establishing documented evidence, which provides a high degree of assur-
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Table 3 Compendial Tests and Standards for APIs
Aspect and macro appearance, including color, odor, and taste
Infrared and ultraviolet spectroscopy, including specific optical rotation, refractive index,
and Raman spectral analysis
Particle morphology, including scanning electron microscopy
Particle size distribution, including light scattering methods and optical microscopy
X-ray diffraction
Thermal methods of analysis, including differential thermal analysis and differential
scanning calorimetry (DSC)
Chromatographic identity and purity, including thin layer chromatography (TLC), gas
chromatography (GC), and high-performance liquid chromatography (HPLC)
Loss on drying and moisture content (Karl Fischer)
Residue on ignition
Specific surface area (BET adsorption isotherm)
Bulk or apparent powder density (loose and tap)
Powder flow and compressibility characterization
Heavy metals and arsenic content
Solubility characteristics in suitable solvents, including color and clarity evaluation
pH value if API is soluble in water
Microbial limits testing
ance, that a specific process (i.e., the manufacture of an API) will consistently
produce a product meeting its predetermined specifications and quality attributes.”
The process for making an API consists of a series (flow diagram in
logically defined steps) of unit operations (modules) that result in the manufacture
of the finished API.
There is much confusion as to what process validation is and what constitutes
validation documentation. We use the term validation generically to cover
the entire spectrum of CGMP concerns, most of which are essentially facility,
equipment, component, methods, and process qualification. The specific term
process validation should be reserved for the final stages of the development
and product scale-up sequence.
The end of the development and scale-up data generation sequence that
should be assigned to the formal, protocol-driven, three-batch process validation
derives from the fact that the specific exercise of process validation should
never be designed to fail. Failure in carrying out the formal process validation
assignment is often the result of incomplete or faulty understanding of process
capability; in other words, what a given process can and cannot do under a
given set of operational requirements. The formalized, final three-batch validation
sequence is used to provide the necessary process validation documentation
Copyright © 2003 Marcel Dekker, Inc.
required by the FDA to show API reproducibility and a manufacturing process
in a state of control (Table 4).
A. Recordkeeping
The first step toward validation is to establish a recordkeeping system that considers
all aspects of the manufacturing process, including controls (or testing).
A recordkeeping system must be established, if it does not exist already, to
provide written records for the validation operations to be conducted. In order
to duplicate a favorable result and prevent duplication of an unfavorable result,
we must document the operations performed so that we have records that we
can review, interpret, and pass judgment on. We cannot rely on memory and
word of mouth. The system of recordkeeping has multiple facets.
1. Standard operating procedures (SOPs) are written procedures that describe
how to perform basic operations in a plant. They explain certain
minimum requirements to assure that there is a level of control
Table 4 Summary of the FDA Guide to Inspection of API Manufacturing
1. Prevent contamination/cross-contamination (need separate air-handling system).
2. Water systems/air quality (potable water acceptable for nonsterile operations).
3. Aseptic/sterile processing. (EtO is acceptable.)
4. Multipurpose equipment/cleaning/closed systems—acceptable for storage outdoors.
5. Protect environment against waste.
6. Cleaning of product contact surfaces (cleaning procedure/sampling plan/analytical
method); limits: practical, achievable, and verifiable.
7. Raw materials. (Storage inside and outside is acceptable.)
8. Containers, closures, and packaging components.
9. Mother liquors. (Secondary recovery is acceptable.)
10. In-process blending/mixing. (Blending off out-of-spec material is not acceptable.)
11. Reprocessing (investigation and reason for failure).
12. Validation (variations that affect chemical/physical/microbial characteristics—establish
relevance and reproducibility).
13. Process change control system in place.
14. Control product/process impurities.
15. In-process testing.
16. Packaging and labeling.
17. Expiry dating and stability data.
18. Laboratory controls and analytical methods validation.
Note: Revised March 1998 and revised by the International Conference on Harmonization, Nov.
2000.
Copyright © 2003 Marcel Dekker, Inc.
that is necessary to operate the process and as a foundation for validation.
These procedures should be written in language that is simple
enough for an untrained nonprofessional to understand. Also, any new
personnel with minimal experience should be able to understand and
follow these procedures. They are applicable to many different phases
of a manufacturing operation.
a. Facilities. One type of SOP applies to the physical facilities of
the plant. Procedures must be written that include frequency and
a list of what must be done and how it is to be accomplished.
Often it is important to keep a log that indicates the dates on
which certain operations are done and the individuals who perform
the operations. Every plant is different, and the types of
products manufactured in each facility may be totally different.
Written SOPs must cover all operations performed within a plant,
with emphasis given to preventing potential problems in a specific
plant based on knowledge of the physical facility, the nature
of the products and materials used, and the personnel employed.
There must be cleaning procedures; first, for cleaning the
walls, floors, and ceilings. They must include frequency of cleaning,
the different steps that are required, and the cleaning agents
acceptable for use. Different areas within a plant will require different
SOPs. For example, a sterile filling room will require more
elaborate cleaning than a warehouse. A prototype SOP is illustrated
in Figure 5.
Another SOP category related to the physical facility is environmental
control. All plants must be kept free of rodents and
insects. Such an SOP will indicate acceptable materials to be
used, precautions to prevent product and personnel contamination,
frequency, and area-monitoring procedure. In some operations,
such as an area to manufacture sterile products, there are
requirements for control of air temperature, humidity, flow rates
and patterns, and particulate matter. These SOPs require steps
such as checks to be performed, including temperature reading
and frequency, maintenance to be performed, such as changing
air filters and frequency, recording instrument checks, and calibration,
such as for temperature and frequency. A prototype SOP
is illustrated in Figure 6.
A third SOP category relating to the physical facility covers
the plant maintenance function. The key consideration in these
SOPs for manufacturing the highest-quality products most efficiently
is preventive maintenance. Correcting a breakdown in a
plant support system (e.g., a motor burned out because it was
Copyright © 2003 Marcel Dekker, Inc.
Figure 5 Facility cleaning procedure.
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Figure 6 Equipment cleaning procedure.
never oiled) is not maintenance but repair, which is generally
more costly. Preventive maintenance SOPs in a plant should
cover the basic air-handling systems, water systems, such physical
structures as walls and ceilings, the waste removal system,
and the heating and cooling systems. They should include replac-
Copyright © 2003 Marcel Dekker, Inc.
ing worn parts, lubrication, replacing filters, cleaning traps, and
checking for leaks.
Safety represents the fourth type of SOP related to the general
facility. When unsafe conditions are present in a plant, the probability
that an accident will occur increases. Besides the fact that
personnel will be affected detrimentally, an accident may occur
and unknowingly affect a product batch. For example, a person
carrying a container of waste material may slip and fall and simultaneously
spill some waste into an open container of a product
batch without being aware that this contamination has occurred.
It is prudent to establish SOPs to include such safety concerns as
clean up of spills; the importance of dry floors; the proper storage
of hazardous materials, such as flammable solvents; personnel
practices, such as running; emergency evacuation of the plant;
and plant safety inspections. A program of SOPs such as these
will also aid in increasing employee morale, as the employer
shows that he is concerned about the personal well-being of the
plant employees. High morale is a very important factor in producing
quality products.
Housekeeping is the fifth category of SOP that relates to the
basic facility. Housekeeping is concerned with keeping materials,
especially those in storage, neat and orderly and always identifiable.
Proper housekeeping provides better efficiency and minimizes
mix-ups. A warehouse that is organized with pallets properly
aligned and not tipped, with adequate aisle space to move
materials and properly segregate different items, will be less apt
to use unauthorized material or ship a customer the wrong product.
In a label storage room that segregates labels well and in a
neat and orderly manner, there will be small risk of the wrong
label being issued. Issuing the wrong label for a product batch
after a considerable investment in validating a process to produce
the highest quality product is a very unfortunate problem and not
an uncommon one. Housekeeping is important to all the operations
conducted in a plant.
b. Equipment. A second type of SOP relates to the equipment used
to manufacture product batches. Equipment includes tanks; mixers;
utensils; scales; pumps; measurement devices for temperature,
pressure, and speed of movement; lyophilizers; tableting machines;
ovens; mills; sterilizing chambers; encapsulators; filling
machines; labelers; conveyor systems; laboratory instruments,
such as pH meters, spectrophotometers, gas chromatographs; and
HPLC systems.
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One category of these SOPs describes equipment cleaning. The
same type of information is required as in facility cleaning, except
as related directly to the equipment involved. Standard operating
procedures must describe what is to be done step by step,
along with disassembly and assembly, frequency, and acceptable
cleaning agents.
The third category of equipment SOPs describes maintenance.
These SOPs are similar in nature except that they relate specifically
to equipment used in production and testing. Highlights of
these procedures include preventive maintenance by lubrication,
replacement of worn parts, disassembly and cleaning, oil and filter
changes, and inspection of problems.
Equipment operation is another category of these SOPs. This
type of procedure is applicable to more complex types of equipment,
but not to all. Obviously we would not need an operating
procedure for a stainless steel tank, but would for a lyophilizer.
These SOPs provide a detailed step-by-step sequence of operations
to run a piece of equipment. They begin with equipment
assembly, then operation, and finally equipment disassembly.
c. Calibration. Standard operating procedures are needed for all
measuring equipment. Temperature, pressure and speed of movement,
and weights are typical measurements performed on production
equipment. There are many different types of instruments
in the control operations that perform measurements (e.g., pH,
dissolution rate, chemical assays, tablet hardness, optical rotation,
and optical density). Some measurements are taken routinely with
a gauge (e.g., a thermometer) and some with recording devices
(e.g., a temperature recorder). In either case, the gauge or recording
device must be calibrated periodically with a reliable standard
such as a National Bureau of Standards traceable source. An example
of this type of SOP is illustrated in Figure 7.
d. Personnel. A third type of SOP relates to the personnel in a plant
who are involved directly in the manufacturing and control process.
We have described many different types of procedures and
the steps to be performed. We have not indicated the personnel
to be responsible for these operations, however. All personnel in a
plant who are involved in the manufacturing process—especially
production, maintenance, and control—should have specific written
job descriptions. As part of the SOP system, these job descriptions
must be very clear in indicating a person’s responsibilities
and duties. A porter must understand very clearly which areas
are to be cleaned and how this is to be accomplished. A produc-
Copyright © 2003 Marcel Dekker, Inc.
Figure 7 Calibration procedure.
tion line operator must understand which lines to work on, what
he or she is responsible for, and when to call on other employees.
The operator must fully understand, for example, whether to
clean a spill on the line or call a porter. In addition to knowing
their duties, all individuals must be intimately familiar with the
different SOPs that are required to perform their job. Standard
Copyright © 2003 Marcel Dekker, Inc.
operating procedures should not be written to be kept in the company’s
files; they should be used by personnel performing their
respective functions and at times even posted.
Other categories of personnel SOPs include personnel practices
and cleanliness. In a pharmaceutical plant, there must be
established rules and regulations regarding proper dress (e.g., uniforms
and hats, safety glasses, hard hats, jewelry, smoking, eating
and drinking, storage of personal articles, and hand washing). A
very important SOP is the one that describes personnel training.
All newly hired personnel should participate in training in their
job responsibilities, all related SOPs, company rules and regulations,
and CGMP regulations. After initial training there should
be a continued routine program to emphasize the information that
employees must not forget and to update any changes.
e. Control. The last type of SOP includes procedures that are more
general and not covered by the other three types. Many of these
SOPs refer to basic good business principles and some relate to
basic control of the manufacturing operation. These procedures
include receipt, sampling, and storage of components to assure
that every raw material and packaging component is inspected on
receipt, sampled, stored on hold, tested and released, or rejected
and placed in approved or reject storage; stability testing to assure
that there are adequate data to support the stated expiry dating
of a product and a continual program to assure product batch
reproducibility; rotation of stock to assure that the oldest raw material
lot is used first or the oldest product batch is shipped first;
and product sampling to assure that samples of the correct number
and size are withdrawn from the appropriate number of containers
with proper microbiological control.
The SOPs described have by no means mentioned all those
required in a manufacturing plant. They do, however, satisfy basic
requirements and should provide insight so that areas in the
specific organization for which SOPs are needed can be identified.
It should always be remembered that more than one individual
must be capable of performing a given task; at times he or
she will be on vacation or absent because of sickness. In addition,
an individual should not be relied on to perform tasks from memory,
as there is no guarantee that such operations will be performed
as reproducibly as may be required. Certainly no two individuals
performing an operation from memory will do it
identically. Written SOPs are necessary to avoid these pitfalls.
Also, a written record provides a history that can be read and
Copyright © 2003 Marcel Dekker, Inc.
studied if, for example, a product batch should fail and we seek
to identify the cause.
2. Specifications, the second set of records, are parameters that describe
the characteristics of a particular material. Each parameter has an acceptable
range that is measurable using a given test procedure. For
example, a raw material may be purchased as a free-flowing powder.
There may be a specification for water content that requires that when
a sample of raw material is analyzed using a given test procedure the
water content cannot be more than 1.0%. If the assay exceeds this
specified limit, the raw material lot is to be rejected. Sometimes a
specification stipulates a minimum level, such as an assay of no less
than 97.0%. At other times, a specification may indicate a range such
as a pH of 6.5 to 7.5. Specifications must be written for each raw
material, packaging component, in-process material, and finished
product. They provide a yardstick by which we can analyze a material
and evaluate whether it is desirable or undesirable. In the case of a
component lot (raw material or packaging component), specifications
enable us to judge whether or not we should use the lot to prepare a
product batch. They provide a basis for comparison to previous lots
received. The specifications for in-process material or finished product
are a yardstick that enables us to determine whether or not the
batch was manufactured properly.
Several officially recognized compendia describe specifications for
components and finished product (e.g., U.S. Pharmacopeia, Food
Chemicals Codex, British Pharmacopeia, and European Pharmacopeia).
These specifications have been established by an advisory
board to each compendium and represent the views of many manufacturers
and government based on a history of the component or product.
Such specifications are reviewed and updated as the need arises
when new information becomes available. These compendia are very
useful and should always be used as a guide whenever possible. In
the case of the USP, for example, if a monograph exists for a component
or product, U.S. drug manufacturers are required to satisfy those
specifications as a minimum requirement.
Sometimes compendia do not contain a monograph for the specific
item that we are interested in. We can use the compendia as guides,
following the specifications established for similar items. Then we
must use our judgment to establish parameters that the material should
be tested for based on our knowledge of the chemistry of the material.
The next step is methods development, to derive a test procedure that
enables us to measure each parameter. By testing different lots of the
material we can establish a specification for the parameter. This work
Copyright © 2003 Marcel Dekker, Inc.
can be done in-house if your organization has the technical expertise
and instrumentation that is needed. If not, outside consultant firms are
available to assist.
Specifications have been established for several pharmaceutical ingredients.
Figure 8 shows prototype specifications for an API that is
commercially available as a solid and listed in the USP. Figure 9
shows an example of a liquid pharmaceutical excipient whose noncompendial
specifications were developed by the supplier.
According to the International Conference on Harmonisation (Federal
Register 65(25) 83041 (Dec. 29, 2000 notices)) specifications for
APIs should cover the following categories:
a. Description (state and appearance of the substance)
b. Identification, such as spectrophotometry, chromatography, colorimetry,
or optical activity
c. A specific stability indicating assay method for testing purposes
d. Impurity profile, including both organic and inorganic substances
Specifications are important in validating both raw materials and
processes. They must be written and followed, unless there is just
cause to change them. Specifications are normally used to screen out
inferior and unacceptable materials. Sometimes the defect can’t be
identified because it was not considered initially in the original specifications.
It is extremely important to understand the chemistry of the
pharmaceutical ingredients that are used and to devote careful attention
to setting specifications for them. Revision and upgrading of
specifications may be required, but should be done in a thoughtful
manner.
3. Test procedures are written procedures that provide the step-by-step
details of how to perform the tests indicated in specifications or SOPs.
They indicate the reagents to be used, sources of the chemicals, how
the reagents are to be prepared, and the shelf life of the reagents.
Also described are the apparatus to be used and special handling and
precautions to be followed. At times a compendial test procedure is
not in sufficient detail for a laboratory technician to follow exactly.
In such a case, the procedure should be written in the necessary detail.
A laboratory technician should not run a test without having the
proper written procedure.
4. Batch records are listings of raw materials, by name and quantitative
(weight or volume) measure, of a unit measure of finished product.
Most manufacturers assign a code number to each raw material to
provide a shorter way to refer to the raw material in batch records
and labels, especially if such systems are computerized. The system
consists of two separate records—a master instruction sheet and a
Copyright © 2003 Marcel Dekker, Inc.
Figure 8 API specifications for acetaminophen.
Copyright © 2003 Marcel Dekker, Inc.
Figure 9 Excipient specifications for linseed oil.
Copyright © 2003 Marcel Dekker, Inc.
data sheet that is used to record various operating parameters. For the
purpose of GMP compliance, the data reported should be accurate and
be able to meet the requirements of a validated master batch record.
The following elements should be included in a typical API master
batch record:
a. Identification of critical processing steps
b. Batch revision number and date
c. Additional data sheets (not part of the approved master batch
record)
d. Step-by-step production and control instructions, acceptable operating
ranges and conditions, in-process specifications, and precautions
to be followed
e. In-process sampling requirements
f. Justified limits or holding times for specific unit operations and
the final product
g. Lot definition and final blend procedures
h. Yield calculation at appropriate steps in the process comparing
actual vs. theoretical yield
5. Manufacturing instructions are the written procedures that personnel
follow during actual product batch preparation. The instructions must
document the modular equipment and materials to be used as well as
the unit operations to be performed. (See Figs. 3 and 4.) The master
document should also include step-by-step manufacturing instructions
as well as GMP-required elements previously listed under the section
on batch records.
6. The approval process is the last and most important part of recordkeeping.
All documents must be approved before they are used. If
they require a change, the documents must again be approved before
the change is implemented. One type of problem discussed earlier
identifies the need for and importance of written records. Now we
must focus our attention on the dilemma created if the records are
wrong or if they become obsolete. Once a document has been approved
and issued, it is the responsibility of the respective personnel
to use it and follow it. No change should ever be permitted without
observing an established approval procedure, because that defeats the
purpose for the document in the first place. If a procedure is to be
changed, several designated individuals should be aware of the need
for change. It does no good if one person changes a procedure and
the others who use it (or those who approved it) are not made aware
of the change.
A manufacturer must establish a list of approvals required for its
records, a list that is not unmanageable yet provides adequate assur-
Copyright © 2003 Marcel Dekker, Inc.
ance that a signed document is meaningful. Theoretically, at least two
signatures are required on such documents—one representing production
and one quality control. Generally there is also another signature,
that of the one who either wrote the procedure or initiated the change.
A manufacturing organization must designate a list of individuals appropriate
to its own operation; however, it is important to remember
that changing an established procedure indiscriminately in the midst
of a serious product problem without bringing the matter to the attention
of the proper individuals may do more harm than good. Effecting
a short-range solution with no thought of the long-range effect can be
damaging.
V. DRUG MASTER FILE
A drug master file (DMF) is defined as a reference source providing detailed
information about a specific facility, process, or article used in the manufacture,
processing, packing, or holding of a (drug) substance that is the subject of an
investigational new drug application (IND), a new drug application (NDA), an
abbreviated new drug application (ANDA), or antibiotic form 6 or 7. Drug master
files originated in 1943 with the submission of information of a chemical
substance to support a drug product application, apparently to ensure confidentiality
of the chemical process for making the chemical substance.
The basic requirements for a type II DMF submission for an API, a drug
substance intermediate, and any material used in the preparation of a drug product
consists of the following elements:
Disclosure of the company and its operations
Description of the facilities and equipment used in the manufacturing process
Description of the sanitation systems on the premises for cleaning and
disposal
Organization, qualifications, and training of personnel
Description of raw materials and packaging components, including specifications,
procedures, and control documentation
Description of quality control and testing procedures
Description of sterile products manufacture and control, if applicable
Description of the quality assurance program
Stability program documentation
Environmental impact assessment statement
Notification of changes or amendments to the DMF
Letter of authorization to make reference to the DMF
Copyright © 2003 Marcel Dekker, Inc.
Statement of commitment to comply with the information contained
within the DMF
The past resistance to the validation of APIs is that much of the required
information and documentation should be contained within the scope and requirements
of a successfully completed DMF. A DMF document, however, does
not have the legal weight of the CGMP regulations, which provide the basis for
requiring API validation documentation.
VI. CHIRAL APIs
According to the FDA guideline for marketing chiral drugs (APIs) issued in
May 1995, drug companies have the choice of developing chiral drugs as racemates
(50% mixture of the D and L forms or enantiomers) or as individual
single enantiomers. Enantiomers have opposite rotational optical activity in solution.
Most companies today have decided to move toward the development of
pharmaceutically active single enantiomers. If the racemate had been approved
alone or in a pharmaceutical dosage form, the development program for the
single active enantiomer can be shortened.
Certain chiral APIs, however, are diastereoisomers and mesocompounds
with two or more optically active centers (carbons) in the molecule (i.e., erythrose,
threose, and mesotartaric acid). In such cases, simplification between racemates
and single enantiomers is often not readily apparent. The conversion of
racemates to active enantiomers can be accomplished using one of the following
reaction pathways:
Lipase immobilized hollow-fiber membranes
Asymmetric dihydroxylation
Asymmetric epoxidation
Fermentation methods for synthesis and resolution
Reaction with cyclic lactam intermediates
Reaction with glycine and aldolase
Fractional crystallization
The advantage of the active enantiomer is that in most cases its activity
is twice that of the racemate and its toxicity potential is one-half. The potency
stability of the active API enantiomer both in the solid state and in solution is
an important concern to be addressed during process validation.
VII. STABILITY OF PHARMACEUTICAL INGREDIENTS
A formal testing program should be established in order to determine the stability
characteristics of APIs. Similar but less stringent stability testing procedures
Copyright © 2003 Marcel Dekker, Inc.
can be set up for pharmaceutical excipients as well. The results of such testing
are used to determine appropriate storage conditions and expiry dating requirements.
The testing program should include sufficient batches, sample sizes, and
testing intervals, plus appropriate storage conditions and a stability indicating
test method in order to obtain relevant stability data for pharmaceutical ingredients
per se.
When pharmaceutical ingredients (both active and excipient) are made
part of a pharmaceutical dosage, they are now components of a separate drug
product stability program.
The testing requirements for pharmaceutical ingredients are similar to
those for drug products.
Stress testing is used to determine the intrinsic physical and chemical
stability of the pharmaceutical ingredient under accelerated, elevated
temperature storage conditions, such as 50°C- 75% RH, 40°C- 75%
RH, and 30°C- 60% RH.
Testing frequencies under accelerated storage conditions are usually 0-, 1-,
3-, and 6-month intervals or longer-term stability testing every 3 months
during the first year and semiannually thereafter at ambient temperature
conditions.
For substances intended for refrigerated or freezer storage: 25°C-60%RH
and 5°C and ?15°C at ambient relative humidity (RH) are used.
In the case of photostability testing the pharmaceutical ingredient may be
subjected to xenon, metal halide, near UV, or cool white fluorescent
lamp exposure.
Typical testing for stability studies includes appearance, potency, chiral
assay, and related substances (impurities, degradation products, and
contaminants) by HPLC assay, water content by Karl Fischer, identification
by NIR or NMR, melting point by DSC, plus microbial
testing.
Stress testing is used to help identify degradation pathways under the influence
of accelerated heat, light, and RH conditions in the presence or absence
of air or oxygen. Such stability testing protocols represent an important aspect
of a pharmaceutical ingredient process validation program.
VIII. REPROCESSING
According to the ICH guidance document, introducing an intermediate (key or
final) or API that does not conform to standards or specifications back into the
process by repeating a crystallization step or other physical manipulation (i.e.,
distillation, filtration, chromatography, milling, and drying) that is part of the
Copyright © 2003 Marcel Dekker, Inc.
established manufacturing process is generally considered to be acceptable. If
reprocessing is used quite often, however, the procedure should be made part of
the manufacturing SOP.
Continuing a processing step that in-process control testing indicates to be
an incomplete step is not considered to be reprocessing. Introducing unreactive
material back into a process and repeating a chemical reaction, however, is
considered to be reprocessing, unless the procedure(s) was (were) made part of
the original manufacturing SOP.
In any case, careful evaluation to ensure that the quality of the intermediate
(key or final) or API is not adversely affected through the formation of
additional by-products and impurities is extremely important. Before a decision
is made to rework or reprocess batches that do not conform to established standards
or specifications, an investigation into the reason for nonconformance
should be carried out. Such procedures should provide impurity profile data for
each reworked or reprocessed batch to be compared to comparable data for
routine manufactured batches. Reprocessing (recycling) means repeating existing
procedures, while reworking is taken to mean making modifications to existing
procedures.
Recovery of reactants, intermediates, or APIs from mother liquors or filtrates
is acceptable as long as the procedures used meet in-process product/
process specifications. Solvents can be recovered and reused as long as the
procedures employed are adequately documented.
IX. RETROSPECTIVE VALIDATION
Retrospective validation of APIs consists of a review and analysis using statistical
process control methods, the physical process parameters, and analytical test
data for immediate past batches (at least the last consecutive lots), and should
include numerical data for starting materials, intermediates (key and final), and
the finished API. Impurity profiles are an important part of such historic data.
The purpose of retrospective validation is to show, through such supporting
documentation process control and reproducibility for intermediates and the finished
API itself. If the data of retrospective validation purposes are faulty, the
regulatory authority expects the manufacturer to conduct appropriate prospective
or concurrent validation studies in accordance with a pre-established, adequate
testing plan or protocol. Such a plan or protocol should identify process equipment,
critical process parameters and their operating ranges, critical characteristics
of the API, sampling plan, and test data to be collected for at least three
consecutive designated batches to demonstrate the consistency of the overall
manufacturing process for the API. In addition, such plans or protocol should
define what constitutes acceptable results.
Copyright © 2003 Marcel Dekker, Inc.
X. REVALIDATION
The revalidation of an API process may be initiated at periodic intervals (annually)
or whenever significant changes are made to equipment, systems, or processes.
The revalidation effort will depend on the nature and extent of the
changes made. The evaluation and decisions regarding the need for revalidation
should be documented. Any indication of failure should result in an investigation
to identify the cause and to take necessary corrective action. An assessment
should be made regarding the need for additional formal process validation. In
the absence of changes or process failure, an annual review of data covering
manufactured lots should be made to assess the need for more formal revalidation
studies.
XI. CHANGE CONTROL
Process validation of an API should include an SOP to reassess a process whenever
there are significant changes in the process, equipment, facilities, reactants,
process materials, systems, and so on that may affect the critical quality attributes
and specifications of the API. Such changes should be documented and
approved in accordance with the scope of the change control SOP. The change
control SOP should consist of the following elements:
Documentation that describes the procedure, review, approval, and basis
for formal revalidation studies
Identification of the change and assessment of its likely implication
Requirements for monitoring change and testing needs
Assessment of information and justification for the change
Review and formal approval to proceed
Identification of changes made to the physical and chemical composition
of the API
Possible regulatory action and customer notification
XII. BULK ACTIVES POSTAPPROVAL CHANGES
The FDA recently issued a guidance document concerning bulk actives postapproval
changes (BACPACS), BACPAC I: Chemistry, Manufacturing and
Controls Documentation, which essentially covers key and final intermediates
in API synthesis (U.S. FDA, CDER, and CVM, issued Feb. 2001). Changes
may be made through one of the following reporting categories:
Copyright © 2003 Marcel Dekker, Inc.
Prior approval supplement (PAS)
Supplement—change being effected (CBE)
Annual report (AR)
The guidance document addresses postapproval changes with respect to
semisynthetic drug substances and impurities associated with APIs. The guidance
document covers changes associated with the following:
Site
Scale of the synthetic processes involved
Equipment used in processes
Specifications for raw materials, including final intermediates
Manufacturing process changes involving synthetic steps through the final
intermediates
Changes to the final intermediates and the resulting API will be covered
in the BACPAC II guidance document. Postapproval changes affecting peptides,
oligonucleotides, radiopharmaceuticals, natural materials, and semisynthetic
APIs are not covered by BACPAC at the present time.
Site changes within a single facility where the synthetic pathway remains
unchanged and CGMP procedures are followed need not be filed with the FDA.
They are considered to be AR changes. If the site change involves the final
intermediate, it is considered to be a CBE-type change. If the site is under new
ownership and not listed in the approved NDA, it also requires a CBE-type
change.
Scale changes either increase or decrease in batch size and are considered
to be AR changes as long as the data output is comparable to the original batch
size.
Specific changes related to a new analytical method that provides equal
or greater assurances of quality is also considered to be an AR change.
Manufacturing process changes are those that encompass a wide range of
process-related changes, from the use of different equipment to changes in synthetic
components and procedures. Such changes are considered to be CBE-type
changes.
Multiple changes in site, scale, and manufacturing processes are considered
to be PAS-type changes and require prior approval from the FDA. More
detailed information is provided in the current FDA guidance documents. (See
the Bibliography.)
XIII. OUTSOURCING AND CONTRACT MANUFACTURE
With respect to the pharmaceutical industry, outsourcing and contract manufacture
probably got its start with APIs, final and key intermediates, and other steps
Copyright © 2003 Marcel Dekker, Inc.
in the synthetic process because of the complexity of API manufacture. The
advantages and disadvantages of outsourcing and contract manufacture are presented
as follows:
Advantages
Less expensive to purchase
Access to specialized and new technologies not currently available inplant
Availability from known suppliers with more chemical manufacturing
experience
Disadvantages
Receive delays without proper internal control on the part of the supplier
Requires a commitment on the part of the purchaser to an external audit
for GMP and/or ISO 9000 compliance
Requires more internal quality control on the part of the purchaser beyond
certificate of analysis acceptance
Auditing the contract API manufacturer is important in order to assess the
quality systems used to determine the integrity and quality capability of the
firm, to determine their level of GMP compliance, and assess the level of resources
available to meet preapproval inspections (PAI) and GMP compliance
readiness.
Typical agenda items for discussion with a potential contract API manufacturer
should include the following:
Organizational structure, site history, and review of previous FDA inspections
Overview of the firm’s key technologies, core competencies, and managerial
capabilities
Overview of the site’s facilities, equipment, and potential production capacity
Overview of the firm’s chemical development and analytical testing capabilities
Overview of the firm’s quality assurance and documentation systems
The firm’s proposed plans and time schedule to meet your company’s
objectives and requirements
Do not oppose outsourcing and contract manufacturing strategies. Point
out to corporate management, however, that the ultimate responsibility for API
manufacture rests with the internal operational functions of your company and
not with those of the vendor or supplier.
Copyright © 2003 Marcel Dekker, Inc.
Table 5 Qualification/Validation of Pharmaceutical Ingredients
Process definition
Options: synthesis/fermentation/extraction/purification
Facilities and equipment (unit operations)
IQ (design and installation)
OQ (operating ranges)
PQ (attributes/specs)
Cleaning validation program
Manufacturing SOP and control parameters
Process flowchart and description of chemistry
Personnel training and safety considerations
Quality attributes
Assay and yield
Impurity profile (qualitative and quantitative)
Contaminant profile (qualitative and quantitative)
Physical characteristics of active API (aspect, thermal analysis, particle size distribution,
optical activity, polymorphic forms, moisture content, loss on drying, microbial
content, etc.)
Analytical methods validation
Critical operating parameters
Reactant ratios, reaction time, temperature, pressure, O2/CO2 ratios, pH (amount of
acid or base), impurity concentration, etc.
Ranges for critical operating parameters
Worst-case challenges during pilot laboratory scale-up for yield, stability, and impurities
Control of process components
Raw materials, solvents, catalysts, gases, processing aids, processing water, steam,
packaging materials and bioburden
Process validation protocol
Sampling and testing strategy
What constitutes acceptable in-process and final product
Formal process validation
At least three batches for reproducibility
Change control procedures and conditions for revalidation, reprocessing, and recovery
validation documentation
Include all pertinent data and reports from design, qualification, and validation stages
Copyright © 2003 Marcel Dekker, Inc.
XIV. CLEANING VALIDATION
Based upon ICH guidelines, cleaning procedures should be validated. Cleaning
validation should be directed toward processing steps in which possible contamination
or material carryover poses a risk to API quality. If residues are removed
by subsequent purification steps in the process, cleaning procedures can be less
rigorous.
Cleaning validation protocols should describe the equipment to be
cleaned, procedures, materials, acceptance criteria, parameters to be monitored
and controlled, and the analytical methods to be employed for testing. Validation
of cleaning procedures should reflect equipment to be used for key and
final intermediates and APIs. The selection of cleaning procedures to be employed
should be based on material solubility and cleaning difficulty. The calculation
of residue limits should consider the potency, toxicity, and stability of
critical materials.
Validated analytical methods should have sufficient sensitivity to detect
residues or contaminants. Residue limits should be practical, achievable, verifiable,
and based upon the most deleterious residue. All cleaning procedures
should be monitored at appropriate intervals to ensure that these procedures are
effective during routine production.
XV. QUALIFICATION/VALIDATION OF PHARMACEUTICAL
INGREDIENTS
A summary of the critical aspects of the process validation of pharmaceutical
ingredients is presented in Table 5.
BIBLIOGRAPHY
Avallone, H. L. GMP inspection of drug substance manufacturers. Pharm Tech (June
1992).
Berry, I. R., Harpaz, D. Validation of Active Pharmaceutical Ingredients. 2nd ed. Denver:
IHS Health Group (2001).
Fabian, A. C. Global harmonisation of GMPs for APIs. Pharm Tech (June 1999).
FDA/ISPE. Baseline Pharm. Eng. Guide. Vol. 1, BPCs (June 1996).
FDA (CDER). Guidance for Industry, ANDAs: Impurities in Drug Substances (June
1998).
FDA (CDER). Guidance for Industry, BACPAC I: Intermediates in APIs (Feb. 2001).
FDA (CDER). Guidance for Industry: Manufacturing, Processing & Holding of APIs
(March 1998).
Fry, E. M. FDA perspective on BPCs. Pharm Tech (Feb. 1984).
Copyright © 2003 Marcel Dekker, Inc.
Gold, D. H. GMP issues in API manufacture. Pharm Tech (April 1992).
Goode, S. A. IPEC GMP audit guideline for BPCs. Pharm Tech (Aug. 1999).
Handbook of Pharm. Excipients. 3rd ed. APhA & London Pharmaceutical Press (2000).
Hirschorn, J. O., Flanigan, T. Global GMP regulations for BPC facilities. J cGMP Comp
4(4), (July 2000).
International Conference on Harmonisation (ICH). GMP Guide for APIs (Nov. 2000).
International Conference on Harmonisation (ICH). Guidance for Industry: Photostability
Testing of Drug Substances (Nov. 1996).
International Pharmaceutical Excipients Council (IPEC). GMPs for Excipients (1995).
Martinez, Rivera, E. FDA perspective on BPC GMPs. Pharm Eng (May/June 1994).
Pharm. Inspection Convention (PIC). GMP Guidelines for APIs Manufacturers (July
1997).
Tuthill, S. M. BPCs GMP. Pharm Tech (Feb. 1979).
Wintner, B. Environmental controls in the pharm. Industry. Pharm Eng (April 1993).
Yu, L. W. Selecting a contract API Co. Amer Pharm Outsourcing, (July/Aug. 2001).
Copyright © 2003 Marcel Dekker, Inc.
12
Qualification of Water and Air
Handling Systems
Kunio Kawamura
Otsuka Pharmaceutical Co., Ltd., Tokushima, Japan
I. PURPOSE OF VALIDATION
High-quality water and air are essential for the manufacture of pharmaceuticals.
Water is the most commonly used raw material in pharmaceutical manufacturing;
it is indirectly used in the manufacture of all dosage forms for cleaning
manufacturing equipment, and is also used as a major component which constitutes
injectable products. It is the one raw material that is usually processed by
the pharmaceutical manufacturer prior to use because it cannot be used as supplied
by the vendor. Water should be regarded as one of major raw materials for
the manufacture of pharmaceuticals whether or not it remains as a component of
the finished dosage form or is eliminated during the manufacturing process.
Water is thus an important raw material in GMP and in validating the manufacturing
process.
Air supplied to the pharmaceutical manufacturing area or the air in the
environment of the pharmaceutical manufacturing area always contacts with
pharmaceuticals, and the quality of air influences the quality of the pharmaceuticals
manufactured, particularly in their cleanliness, particulates, and microbial
quality. Temperature and humidity in the manufacturing environment also influence
the quality of the pharmaceuticals manufactured.
The importance of air quality and air handling system are described in
CFR 211-46 as part of GMP.
The USP identifies several grades of water that are acceptable for use in
pharmaceuticals, and also defines the quality of the environment or the quality
of air for the manufacturing of pharmaceuticals according to its criticality.
Copyright © 2003 Marcel Dekker, Inc.
Water and the environment must be periodically monitored for these quality
attributes, and in some instances the results are not available for days after
the sample is obtained. Meanwhile, the water would have been used to manufacture
a great number of pharmaceutical products or else the products would have
already been exposed to the environment. Water treatment and air handling
systems are highly dynamic, and careful attention has to be paid to their operation,
even though this may sometimes be somewhat unreliable. Consequently,
they must be validated and then closely monitored and controlled.
Validation is defined as “a documented program that provides a high degree
of assurance that a specific process, method, or system will consistently
produce a result meeting pre-determined acceptance criteria” [1].
The purpose of validation is to demonstrate the capability of the water
treatment and air handling system to continuously supply the required quantity
of water and air with the specified quality attributes. “Documented” means to
provide documented “evidence.” Validation provides the system owner with the
means of assessing when a water treatment and/or air handling system is operating
outside established control parameter limits and provides a means for bringing
the system back into a state of control. It results in written operating and
maintenance procedures for personnel to follow, which in turn helps ensure
consistent system performance.
II. VALIDATION STRATEGY
A. Validation Concept
The basic strategy is to prove the performance of processes or systems under
all conditions expected to be encountered during future operations. To prove the
performance, one must demonstrate (document) that the processes or systems
consistently produce the specified quantity and quality of water and/or air when
operated and maintained according to specific written operating and maintenance
procedures. In other words, validation involves proving
1. Engineering design
2. Operating procedures and acceptable ranges for control parameters
3. Maintenance procedures
To accomplish this, the system must be carefully designed, installed, and tested
during and after construction, and therefore for a prolonged period of time under
all operating conditions.
Variations in daily, weekly, and annual system usage patterns must be
validated. For example, water may be drawn from the system for manufacturing
use only during normal working hours; there may be no demands on the system
at other times during the 24-hr cycle. The system may be idle on weekends and
Copyright © 2003 Marcel Dekker, Inc.
on holidays, which could extend for as long as 4 days or more. In addition,
many firms have annual plant maintenance shutdowns, typically in the summer,
and systems must be sanitized and restarted prior to use, and of course emergency
shutdowns can occur at any time and the system must be brought back
online. Systems with ion exchange resins (deionizers) must be at least partially
shut down to regenerate the resins when the chemical quality of the treated
water drops below a specified level. (This could be a matter of a few days or
even a few months, depending on the quantity of water processed through the
system and other factors.) For the air handling system, the same kinds of issues
exist. Clean rooms should be maintained at their required cleanliness level, even
during the time of no manufacturing operation. If the cleanliness is broken or
the air handling system stops, the whole clean area has to be made clean according
to the initial validation procedure and assessment. Water treatment and/or
air handling systems must be validated under all of these normal operating conditions
in order to prove the adequacy of the engineering design and the effectiveness
of the operating, control, and maintenance procedures.
B. Validation Life Cycle
1. Determination of Quality Attributes
In performing the validation, defining the quality attributes—that is, gaining a
clear understanding of the required quality and intended use—is the most important
issue, and should be determined before starting the validation. Without
defining required quality attributes we cannot establish validation protocols,
which are the basis of all validation studies.
2. The Validation Protocol
A validation protocol is defined as
A written plan stating how validation will be conducted and defining acceptance
criteria. For example, the protocol for a manufacturing process identifies
process equipment, critical process parameters/operation ranges, product
characteristics, sampling, and test data to be collected, number of
validation runs, and acceptable test results [1].
The validation protocol is a detailed plan for conducting a validation
study. It is drafted by the individual or task group responsible for the project,
reviewed for content and completeness following the firm’s protocol review
procedure, and approved by designated individuals. It describes the responsibilities
of each individual or unit involved in the project.
All protocols, whether for IQ (installation qualification)/OQ (operational
qualification) of new equipment or for validating a new process, have the same
Copyright © 2003 Marcel Dekker, Inc.
basic format. They start with an objective section, which describes the reasons
for conducting the validation study as well as the results to be achieved. Next
there is a scope section. Here what is to be included and excluded from the
study is specified, effectively establishing the boundaries for the study.
Following the objective and scope sections is a detailed description of the
process/equipment to be validated. Here block diagrams of equipment, batch
formula and master manufacturing records, process flow diagrams, and other
documents that will help with the descriptive process are essential and should
be attached to the protocol. The protocol should contain a detailed description
of the sampling and testing schedule and procedures and clearly state the acceptance
criteria for each stage of validation, such as DQ (design qualification), IQ,
OQ, and PQ (performance qualification). The number of times that specific
trials will be replaced in order to demonstrate reproducibility of results must be
specified.
The protocol should be endorsed by designated representatives of each unit
that will participate in the validation study. This is an essential step for validation
study. It should be described that the protocol is accepted by responsible persons,
and that each unit understands and agrees to fulfill its responsibilities as stated in
the protocol. Subsequent changes to the protocol, should they be necessary, must
be endorsed by the same individuals. Protocol addenda are sometimes necessary
because circumstances later arise that were impossible to anticipate when the study
was planned and the protocol drafted. In addition to approvals, the validation
protocol should have the appended data sheets, which are to be filled with data
obtained from the validation studies and compared with the criteria.
3. Steps of Validation
Validation plans for water and air systems typically include the following steps
(Fig. 1):
1. Establishing standards for quality attributes of water and air to manufacture
pharmaceuticals.
2. Defining systems and subsystems suitable to produce the desired
water and air by considering the quality grades of water and air.
3. Designing equipment, controls, and monitoring technologies.
4. Establishing standards for operating parameters of the selected
equipment of the system.
5. Developing an IQ stage consisting of instrument calibrations, inspections
to verify that the drawings accurately depict the as-built configuration
of the system, and special tests to verify that the installation
meets the design requirements. These items include pipe and instrument
drawings, air pressure differentials, air velocities, and airflow
patterns.
Copyright © 2003 Marcel Dekker, Inc.
Figure 1 Validation life cycle of water and air system. (From Ref. 2.)
Copyright © 2003 Marcel Dekker, Inc.
6. Developing an OQ stage consisting of tests and inspections to verify
that the equipment, system alerts, and controls are operating.
7. Establishing alert and action levels for the operational standards and
routine control. This phase of qualification may overlap with aspects
of the next step.
8. Developing a prospective PQ stage to confirm the appropriateness of
critical process parameter operating ranges. System reproducibility is
to be demonstrated in this stage over an appropriate time period.
During this phase of validation, alert and action levels for key quality
attributes of water, such as TOC, pH, particulates and microbes,
and operating parameters for an air system (e.g., temperature, time,
air pressure differential, airflow velocity, and air exchange rate) are
verified.
9. Supplementing a validation maintenance program (also called continuous
validation life cycle) that includes a mechanism to control
changes to the system and establishes and carries out scheduled preventive
maintenance, including recalibration of instruments.
10. Instituting a schedule for periodic review of the system performance
and requalification.
11. Completing protocols and documenting steps 1 through 10 [2].
4. Control During Routine Operation
Revalidation and Change Control. Once the validation is completed, the
standard operating procedures (SOPs) are formalized. Routine operation should
be performed according to the established SOP.
Any proposed changes should be evaluated for their impact on the whole
system. The necessity for requalifying the system because of changes should be
determined. Revalidation and evaluation should be performed depending upon
the impact that might be caused by the change.
Alert and Action Levels. Validated and established systems should be
periodically monitored to confirm that they continue to operate within their
design specifications and consistently produce water or air of acceptable quality.
Monitored data may be compared to established process parameters or product
specifications. A refinement to the use of process parameters and product specifications
is the establishment of alert and action levels, which signal a shift in
process performance. Alert and action levels are distinct from process parameters
and product specifications in that they are used for monitoring and control
rather than accept or reject decisions. The levels should be determined based on
the statistical analysis of the data obtained by monitoring at the PQ step.
Alert levels are levels or ranges that when exceeded indicate that a process
may have drifted from its normal operation condition. Alert levels indicate a
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warning and do not necessarily require a corrective action. Exceeding an action
level indicates that corrective action should be taken to bring the process back
into its normal operating range [2,8].
III. QUALIFICATION OF WATER SYSTEMS
A. Required Quality for Water for
Pharmaceutical Purposes
Water is one of the most widely used substances, and raw materials, or an
ingredient in the production, processing, and formulation of pharmaceuticals.
Control of the organic and inorganic impurities and microbiological quality
of water is important because proliferation of micro-organisms ubiquitous in
water may occur during the purification, storage, and distribution of this substance.
Although there are various quality grades of water used for pharmaceutical
purposes, all kinds of water are usually manufactured from drinking water
or comparable grade water as a source water.
Grades of water are closely related to the manufacturing methods and
distribution system of water. Major differences among these grades of water
consist of the following quality attributes:
Microbial counts
Endotoxin, which is due to the presence of microbes
Organic and inorganic impurities
Grades of water specified in the compendia (USP) are classified according
to the above quality attributes as
1. Potable water
2. Purified water
3. Water for injection
4. Sterile water for injection
5. Sterile water for inhalation
6. Sterile water for irrigation
7. Sterile bacteriostatic water for injection
Grades of water specified in the Pharmacopeia (USP) are summarized in
Table 1. “Water for injection” (WFI) is the most purified water, and careful
attention should be paid to the validation of its manufacturing process.
B. Selection of Water for Pharmaceutical Purposes
The quality attributes of water for a particular application are dictated by the
requirement of its usage. Sequential steps that are used for treating water for
different pharmaceutical purposes are shown in Figure 2 [6].
Copyright © 2003 Marcel Dekker, Inc.
Table 1 Specifications of Water for Pharmaceutical Use
Microbial Particulate
Inorganics control Microbial limit matter Endotoxin
Source water (I) ?a ?a ?a ?a ?a
City water (potable) (II) Reg.b Reg.b Reg.b ?a ?a
Purified water (deionized) (III) +c +c 100 CFU/mLd ?a ?a
Purified water (membrane) (IV) +c +c 100 CFU/mLd ?a +
WFI (rinse) (V) +c +c 100 CFU/mLd ?a +
WFI (preparation) (VI) +c +c 100 CFU/mLd +f <0.25 EU/mle
WFI (LVP) (VII) +c +c 100 CFU/mLd +f <0.25 EU/mle
aNo control, no specifications.
bCity water regulations.
cControlled to be less than city water specifications. Microbial counts in deionized water should be carefully controlled.
dAccording to the specifications by USP/EP, and recommended criteria final rinse water: 10 CFU/100 mL.
eCooling water used for sterile products: 1 CFU/100 mL.
fParticulate matter for LVP: (>10 µm, 20/ml), >25 µm, 2/ml).
Copyright © 2003 Marcel Dekker, Inc.
Figure 2 Water for pharmaceutical purposes. (From Ref. 2.)
The manufacturing method and distribution system also have a close relation
with the construction design of facilities and equipment.
1. Selection of the most suitable quality grade of water for its intended use.
2. Determination of the water manufacturing system elements, including
facility and equipment.
3. Design of water manufacturing system, including the design of system
equipment.
4. After construction of the water system is completed based on its design,
the system has to be scrutinized as to whether it has been built
to design specification or not.
Copyright © 2003 Marcel Dekker, Inc.
5. After confirming the installation of facility and equipment, the quality
of water produced is examined from various viewpoints according to
the predetermined specifications.
6. In the routine production of water, representative quality items of water
have to be monitored to confirm the performance of normal operation,
and if any undesirable trends or out of specification values are
found, corrective action should be taken.
The steps of checking design and construction, confirming proper installation
and operation, and documenting these processes are collectively called qualification
or validation. In case of any system change or changes to equipment,
the same kinds of procedures should be implemented.
Water for pharmaceutical purposes, and selection of water grade for pharmaceuticals
are summarized in Figures 1 and 2. Specifications of various kinds
of water are summarized in Table 1.
Major items of quality attributes that should be controlled and specified
for pharmaceutical use are
1. Organic impurities
2. Inorganic impurities
3. Particulates
4. Microbes
5. Endotoxin
C. Design Qualification of Water Systems
The quality attributes of water for a particular application are dictated by the
requirements of its usage. Production of pharmaceutical water employs a combination
of sequential unit operations (processing steps) that address specific water
quality attributes.
The validation plan should be designed to establish the suitability of the
system and provide a thorough understanding of the purification mechanism,
range of operating conditions, required pretreatment, and the most likely mode
of failure. It is also necessary to demonstrate the effectiveness of the monitoring
scheme and to establish the requirements for validation maintenance. The selection
of specific unit operations and design characteristics for a water system
should take into consideration the quality of the feed water, the technology
chosen for subsequent processing steps, the extent and complexity of the water
distribution system, and the appropriate requirements. In a system for WFI, the
final process (distillation, reverse osmosis, or ultrafiltration) must have effective
bacterial endotoxin reduction capability and must be validated for each specific
equipment unit. The final unit operations used to produce WFI have been limited
to distillation, reverse osmosis, and/or ultrafiltration. Distillation has a long
Copyright © 2003 Marcel Dekker, Inc.
history of reliable performance for the production of WFI. Other technologies,
such as reverse osmosis and ultrafiltration, may be suitable in the production of
WFI if they are appropriately validated for each specific set of equipment.
Typical sequential processing steps that are used for manufacturing purified
water (PW) are shown in Figure 3. A distilled water distribution system
that is commonly used for WFI is shown in Figure 4.
1. Step 1 is the combination of prefilter, carbon filter, and ion exchanger
(softener). After chlorine is removed, attention has to be paid to pre-
Figure3 Typical sequential processing steps for water treatment.
Copyright © 2003 Marcel Dekker, Inc.
Figure4 Typical sequential processing steps for distilled water treatment. When cooling
water is not needed, water will circulate at 80°C or above. During use the cooling
water valve is open and the loop outlet valve is closed. After use the loop outlet valve
is kept closed and the loop drain valve opened to flush all the cooled water to drain.
vent microbial growth. For this purpose, ultraviolet light is installed
and the water is circulated.
2. Step 2 is a reverse osmosis process, after adjusting temperatures by
heat exchanger.
After the reverse osmosis process, inorganic impurities are completely
removed by anion exchanger and cation exchanger. An ultraviolet light is installed
and the water is circulated to prevent microbial growth.
The obtained water can be used for nonparenteral dosage forms. For the
parenteral purpose, water obtained in this way is usually distilled.
Water for injection obtained by distillation is circulated through the main
loop and subloop at 80. During use the cooling water valve is open and the loop
outlet valve is closed. After use the loop outlet valve is kept closed and the loop
drain valve is opened to flush all the cooled water to drain.
A typical evaluation process to select an appropriate water quality for a
particular pharmaceutical purpose is shown in the decision tree in Figure 5 [2].
D. Qualification of Equipment and Components
for Water System
Equipment and components used for the water system must maintain sanitary
integrity and be anticorrosive and assured for technical integrity.
Copyright © 2003 Marcel Dekker, Inc.
Figure 5 Selection of water for pharmaceutical purpose. *, Water for sterile BPCs or
dosage forms must be rendered sterile if there is not a sterilization step following addition;
‡, microorganism control can occur either in water treatment or in BPC process; †,
endotoxin removal can occur either in water treatment or in BPC process; §, NPDWR
water—water meeting EPA national primary drinking water regulations. (From Ref. 2.)
Copyright © 2003 Marcel Dekker, Inc.
1. Components
Selection should be made with assurance that it does not create a source for
contamination intrusion.
2. Piping and Installation
Stainless steel welds should provide reliable joints that are internally smooth
and corrosion-free. Low carbon stainless steel (SUS 304L, 316, and 316L) compatible
wire filler, and where necessary, inert gas, automatic welding machines,
and regular inspection and documentation, help to ensure acceptable weld quality.
Follow-up cleaning and passivation are important for removing contamination
and corrosion products and to re-establish the passive corrosion-resistant
surface. Piping systems should be installed and sloped in such a way that they
are completely self-draining. Complete drainage is important, as it prevents the
formation of standing “pools” of liquid that can support the growth of microbes.
Further, properly sloped piping prevents the formation of condensate “plugs”
that can cause cold spots during SIP, and most important it allows for the free
drainage of all rinsing and washing solutions during CIP, which enhances cleaning
efficiency. The slope is normally 1/200 to 1/100. Isometric drawings of
piping systems for water systems are essential for the design and installation
qualification of both water supply and CIP/SIP piping systems.
3. Material
Materials of construction should be selected to be compatible with materials
used as control measures, such as sanitizing, cleaning, and passivating
media.
Plastic materials can be fused (welded) in some cases and also require
smooth, uniform internal surfaces. Adhesives should be avoided due to the potential
for voids and chemical reactions. Mechanical methods of joining, such
as flange fittings, require care to avoid the creation of offsets, gaps, penetrations,
and voids. Control measures include good alignment, properly sized gaskets,
appropriate spacing, uniform sealing force, and the avoidance of threaded fittings.
Temperature rating is a critical factor in choosing appropriate materials
because surfaces may be required to handle elevated operating and sanitization
temperatures. Should chemicals or additives be used to clean, control, or
sanitize the system, materials resistant to these chemicals or additives must be
utilized.
4. Surface Polishing
The finish on metallic materials such as stainless steel, whether it be a refined
mill finish, polished to a specific grit, or an electropolished treatment, should
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complement system design and provide satisfactory corrosion and microbial activity
resistance.
5. Dead Legs
Dead legs pose two problems for CIP. First, cleaning fluids must be able to
flush out trapped gas pockets in order to wet all the piping surfaces in the dead
legs. Second, fresh cleaning fluid must flush the dead leg to maintain rapid
cleaning rates. Dead legs should not be greater in length than six diameters (6D)
of the unused portion measured from the axis of the pipe in use.
6. Valves
The most commonly used valves in process piping systems for PW and WFI
used for pharmaceutical manufacturing are diaphragm valves. This is because
they are easily CIP-cleanable and provide complete containment of in-process
materials. Diaphragm valves are limited in the ways they may be installed for
free drainage; they sometimes are prone to leakage and they have a relatively
high pressure drop as compared with other types of valves.
For situations in which complete containment is not required, “plungertype”
compression valves of hygienic design may be used. These have several
advantages over diaphragm valves regarding installation and operation but they
do not provide complete containment.
Ball and butterfly valves are also commonly used in water treatment systems.
Diaphragm valves should be used downstream from the unit that removes
dissolved solids (reverse osmosis unit or deionizer), however, because of their
inherent ease of sanitation.
7. Pumps
Pumps should be of sanitary design with seals that prevent contamination of the
water. Pumps moving water for manufacturing or final rinsing, water for cooling
the drug product after sterilization, and in-process or drug product solutions
shall be designed to utilize water for injection as a lubricant for the seals. Several
types of CIP-cleanable pumps are commonly used in water systems or pharmaceutical
manufacturing processes. These include centrifugal, rotary lobe, peristaltic,
and diaphragm pumps, of which all but the centrifugal pump provide
positive displacement.
8. In-Line Instrumentation
In-line instruments or sensors are necessary components for automated processes.
For ease of cleaning, sensors should be chosen that directly mount onto
vessel nozzles or piping tees with minimum dead leg distances. Also, the instru-
Copyright © 2003 Marcel Dekker, Inc.
ments should be of a cleanable design and constructed to similar standards as
those for process equipment and piping.
9. Pressure Gauges
Sanitary diaphragm-style pressure gauges should be used when possible, as they
are very cleanable. When pressure gauges are installed in process piping, the
diameter should be less than 6D.
10. Heat Exchangers
Heat exchangers should be double tube sheet or concentric tube design. Heat
exchangers other than the welded double-concentric tube type or double-tube
sheet type must employ a pressure differential and a means for monitoring the
differential. The pressure differential shall be such that the fluid requiring a
higher microbial quality shall be that with the greater pressure.
11. Distillation
Distillation equipment is used to produce USP WFI-quality water. The distillation
process removes dissolved solids not otherwise removed by deionizers or
RO units.
The chemical quality of the steam supplied to the still must be controlled
to prevent recontamination of the distillate. Also, the condenser must be of a
double-tube design to prevent condenser coolant from coming into direct contact
with the distallate, thereby causing recontamination.
Separation of mists by the distillation process is important to remove the
endotoxin or other contaminant. Distillators have their own upper limits of
throughput capacity. Usually the more the amount of water generated at the unit
period, the more the conductivity increases at the range of maximum capacity.
This means that the purity of the water becomes worse.
12. Filters
Final filters of water for injectable products may not be used at any point in the
piping system of water for manufacturing or final rinse.
Water storage tank vent filters must be equipped with a sterilizing air filter
in order to prevent the air, which displaces water drawn from the tank, from
microbiologically contaminating the water. The filter must be hydrophobic in
order to prevent condensation from blinding the filter and preventing air entry
or escape from the tank. It also must have a mean porosity of less than 1 µm.
Water filters are used in various locations in water treatment systems for
two basic purposes: removal of undissolved solids, some of which are added to
the water by various components of the water treatment system, and removal of
Copyright © 2003 Marcel Dekker, Inc.
bacterial contaminants. Filters are commonly used downstream from carbon
beds and resin beds and on the incoming water supply line, and they are typically
in the order of 10 to 15-µm mean porosity. Membrane filters of 0.2 µm
are used to remove bacteria. Filters must be properly maintained in order to
keep the water treatment system operating efficiently and to prevent them from
becoming a source of bacterial and endotoxin contamination.
Microbes are not destroyed by bacteria-retentive filters but instead become
concentrated in and on them. Certain bacteria have the capability of growing
through a membrane filter. Also, filters can become damaged by frequent or
sudden changes in water pressure (water hammer).
13. Deionizers
These devices are used to remove dissolved solids from the feed water. Dionizers
use ion exchange resins to remove charged particles. Cation resin beds remove
negatively charged particles; anion resins remove positively charged particles.
Mixed bed deionizers (containing both cation and anion exchange resins)
are commonly used to give the water a final “polishing” treatment. Resins lose
their ability to remove charged particles and must be periodically regenerated
using strong caustic and acid solutions. This treatment also sanitizes the resin
beds, which, like carbon beds, are a fertile breeding ground for bacteria when
improperly maintained.
14. Auxiliary Equipment
1. Backflow of liquids shall be prevented at points of interconnection of
different systems.
2. Pipelines for the transmission of water for manufacturing or final
rinse and other liquid components shall be constructed of welded
stainless steel (nonrusting grade) equipped for sterilization with
steam, except that sanitary stainless steel lines with fittings capable
of disassembly may be immediately adjacent to the equipment or
valves that must be removed from the lines for servicing and replacement.
3. Auxiliary equipment and fittings that require seals, gaskets, diaphragms,
filter media, and membranes should exclude materials that
permit the possibility of extractables entry, shedding, and microbial
activity [7–12].
15. Ultraviolet Light
Ultraviolet light (UV) is not effective enough to eliminate existing biofilm.
When coupled with conventional thermal or chemical sanitization technologies,
however, it is most effective and can prolong the interval between system sanitizations.
Copyright © 2003 Marcel Dekker, Inc.
The use of UV light also facilitates the degradation of hydrogen peroxide
and ozone. The most effective biocidal wavelength is 253.7 nm. The amount of
light at 255 nm emitted by a UV light decreases with time, so lamps have to be
monitored and replaced when necessary.
16. Wastewater
Waste liquids shall be introduced to sewers through trapped drains. Drains from
equipment shall be designed with an atmospheric break to prevent backsiphonage.
All stills and tanks holding liquid requiring microbial control shall have
air vents with non-fiber-releasing sterilizable filters capable of preventing microbial
contamination of the contents. Such filters shall be designed and installed
so that they do not become wet. Filters shall be sterilized and installed aseptically.
Tanks for holding water require air vents with filters [7,10].
E. Sanitization
Microbial control in water systems is achieved primarily through sanitization
practices. Systems can be sanitized using either thermal or chemical means. Inline
UV light can also be used to “sanitize” water in the system continuously.
1. Thermal Approaches
Thermal approaches to system sanitization include periodic or continuously circulating
hot water and the use of steam. These techniques are limited to systems
that are compatible with the higher temperatures needed to achieve sanitization,
such as stainless steel and some polymer formulations. Hot water circulation is
effective or essential for this purpose, especially for the WFI system.
2. Chemical Methods
Chemical methods, where compatible, can be used on a wider variety of construction
materials. These methods typically employ oxidizing agents such as
hypochlorite, hydrogen peroxide, ozone, or per-acetic acid. Hypochlorites are
effective sanitizers but are difficult to flush from the system and tend to leave
biofilms intact.
3. Validation of Sanitization Steps
Sanitization steps require validation to demonstrate the capability of reducing
and holding microbial contamination at acceptable levels. Validation of thermal
methods should include a heat distribution study to demonstrate that sanitization
temperatures are achieved throughout the system. Validation of chemical meth-
Copyright © 2003 Marcel Dekker, Inc.
ods requires a demonstration of adequate chemical concentrations throughout
the system. In addition, when the sanitization process is completed, effective
removal of chemical residues must be demonstrated.
The frequency of sanitization is generally dictated by the results of system
monitoring. Conclusions derived from the trend analysis of the microbiological
data should be used as the alert mechanism for maintenance. The frequency
of sanitization should be established so that the system operates in a state of
microbiological control and does not exceed alert levels.
4. SIP/CIP
For a WFI or highly purified water system, the SIP/CIP method is usually applied.
In an SIP/CIP system, sterilization and/or cleaning take in place in situ or
without dissembling the equipment. Consequently, the result of sterilization and/
or cleaning is confirmed by the process parameters previously validated. Based
on process parameters and their ranges previously determined by the process
validation, the SIP/CIP process can be confirmed whether or not it is completely
sterilized and cleaned. This is a typical application of the concept of validation.
5. Hot Water Circulation of WFI System
Hot water circulation systems circulate hot water through all pipelines from the
storage tank through all use points to return to the storage tank. By a combination
of hot water circulation system and SIP, microbial quality of WFI can be
guaranteed to be 0 cfu per 100 ml. Once the water in the system is drained out,
the entire system must be steam-sterilized. By applying hot water circulation
and SIP, formation of any biofilm can be prevented if the piping and installation
are well designed and there are no dead legs [2,7–9,11,12].
F. Sampling Considerations
Water systems should be monitored at a frequency that is sufficient to ensure
that the system is in control and continues to produce water of acceptable quality.
Samples should be taken from representative locations within the processing
and distribution system. Established sampling frequencies should be based on
system validation data and should cover critical areas. Unit operation sites might
be sampled less frequently than point-of-use sites. The sampling plan should
take into consideration the desired attributes of the water being sampled. Because
of their more critical microbiological requirements, systems for WFI may
require a more rigorous sampling frequency.
When sampling water systems, special care should be taken to ensure that
the sample is representative. Sampling ports should be sanitized and thoroughly
flushed before a sample is taken. Samples for microbiological analysis should
Copyright © 2003 Marcel Dekker, Inc.
be tested immediately or suitably protected to preserve the sample until analysis
can begin. The sampling operation itself might often cause a microbial contamination.
1. Biofilm, Planktonic Micro-Organisms, and Benthic
Micro-Organisms
Samples of flowing water are only indicative of the concentration for planktonic
(free-floating) micro-organisms present in the system. The number of microbes
determined by the water system monitoring is an indication of floating microbes
in water; that is, planktonic micro-organisms. Benthic (attached) micro-organisms
in the form of biofilms are generally present in greater numbers and are
the source of the planktonic population.
The major purpose of monitoring microbes is to identify the generation of
biofilms and to find the locations of biofilms, if any. The purpose of sanitization
is to kill and destroy the biofilm after detecting the location of the biofilms. The
planktonic population, whose number of micro-organisms in water is monitored,
should be understood and utilized to indicate biofilms in the system. The number
of microbes in water is an indicator of system contamination levels and is
the basis for the system alert levels.
If there were no microbials in water, there would not be any biofilms in
the system. If any microbials are detected in the system, there must be biofilms
in some locations. Biofilm is formed in stagnant places, such as valves, dead
ends, or unsuitably sloped piping. Detecting micro-organisms and biofilms is
one method of controlling the cleanliness of the system. The other method is to
completely eliminate the stagnant places or dead ends that might cause biofilms.
From such viewpoints, the design and construction of a desirable water system
as described in sec. III.D is the fundamental way to prevent the formation of
biofilms, and consequently to both reduce the number of micro-organisms and
prevent the generation of micro-organisms in the system.
2. Operation, Monitoring, and Control
Monitoring programs should be established to ensure that the water system remains
in a state of control. The program should include
1. Procedures for operating the system
2. Monitoring programs for critical quality attributes and operating conditions,
including calibration of critical instruments
3. Schedule for periodic sanitization
4. Preventive maintenance of components
5. Control of changes to the mechanical system and to operating conditions
Copyright © 2003 Marcel Dekker, Inc.
3. Operating Procedures
Procedures for operating the water system and performing a routine monitoring
program should be established based on the validation study. The procedures
should be well documented, detail the function of each job, assign who is responsible
for performing the work, and describe how the job is to be conducted.
4. Monitoring Program
Critical quality attributes and operating parameters should be documented and
monitored. The program may include a combination of in-line sensors or recorders
(e.g., a conductivity meter and recorder), manual documentation of operational
parameters (such as carbon filter pressure drop), and laboratory tests (e.g.,
total microbial counts). The frequency of sampling, the requirement for evaluating
test results, and the necessity for initiating corrective action should be included.
G. Microbial Considerations
The major exogenous source of microbial contamination is source or feed water.
At a minimum, feed water quality must meet the quality attributes of potable
water for which the level of coliforms is regulated. A wide variety of other
micro-organisms, chiefly gram-negative bacteria, may be present. These microorganisms
may compromise subsequent purification steps. Examples of other
potential exogenous sources of microbial contamination include unprotected
vents, faulty air filters, backflow from contaminated outlets, drain air breaks,
and replacement activated carbon and deionizer resins. Sufficient care should
be given to system design and maintenance in order to minimize microbial contamination
from these sources.
Micro-organisms present in feed water may adsorb to carbon beds, deionizer
resins, filter membranes, and other unit operation surfaces and initiate the
formation of a biofilm [2,8].
H. Endotoxin
Endotoxins are lipopolysaccharides from the cell envelope that is external to the
cell wall of gram-negative bacteria. Gram-negative bacteria readily form biofilm
that can become a source of endotoxin. Endotoxin may be associated with living
micro-organisms or fragments of dead micro-organisms, or may be free molecules.
The free form of endotoxin may be released from cell surfaces or biofilm that
colonize the water system, or they may enter the water system via the feed water.
Endotoxin should be eliminated by means of distillation, reverse osmosis,
and/or ultrafiltration. Generation of endotoxin is prevented by controlling the
Copyright © 2003 Marcel Dekker, Inc.
introduction of micro-organisms and microbial proliferation in the system. This
may be accomplished through sanitization and sterilization.
The presence of endotoxin should be monitored by LAL method in the
routine operation. Endotoxin can be removed by means of distillation, reverse
osmosis, and/or ultrafiltration. Incomplete separation of mist in distillation, however,
and leakage in membrane of reverse osmosis or ultrafiltration cause contamination
with endotoxin. After these separation processes, of course, contamination
of microbes or growth of microbes causes endotoxin contamination [2,8].
I. Methodological Considerations
The objective of a water system microbiological monitoring program is to provide
sufficient information to control the microbiological quality of the water
produced. An appropriate level of control may be maintained by using data
trending techniques and limiting specific contraindicated micro-organisms, consequently
it may not be necessary to detect all of the micro-organisms present.
The methods selected should be capable of isolating the numbers and types of
organisms that have been deemed significant relative to system control and
product impact for each individual system [2,8].
J. Continuous Automatic Monitoring of Water
Monitoring and feeding back the data are important in maintaining the performance
of water systems. By applying an automatic continuous monitoring system
combined with the method of trend analysis, processes can be maintained
in a much more stable state. For example, this can be achieved by applying
automatic continuous monitoring of TOC and conductivity of the water system.
TOC and conductivity are the major quality attributes of water by which
organic and inorganic impurities can be determined.
IV. QUALIFICATION OF AIR HANDLING SYSTEMS
A. Purposes of an Air Handling System
The purposes of an air handling system are
1. To prevent microbial contamination of sterile products and of clean
areas
2. To prevent the spreading and contamination of virus, pathogenic, and
spore-forming microbes used in the manufacturing of pharmaceuticals
3. To prevent spread and contamination of penicillin or other sensitizing
drugs, cytotoxic drugs, and drugs with strong pharmacological action
Copyright © 2003 Marcel Dekker, Inc.
4. To prevent cross-contamination of solid dosage form or bulk pharmaceuticals,
whose fine powder tends to spread and disperse
CFR211.46 states that “a) Adequate ventilation shall be provided.
b) Equipment for adequate control over air pressure, micro-organisms, dust,
humidity, and temperature shall be provided when appropriate for the manufacture,
processing, packaging, or holding of a drug product. c) Air filtration system,
including prefilters and particulate matter air filters, shall be used when
appropriate on air suppliers to production areas.”
In the air handling system, special attention has to be paid to keep the
environment clean and to prevent the contamination of products. There are two
different kinds of concepts to control the air system: one is to prevent intrusion
of the surrounding air (positive air pressure control), and the other is for the
containment of air containing an undesirable substance generated in the operation
area (negative air pressure control). Air handling systems should be designed,
installed, and maintained to meet these purposes.
B. The Concept of Air Handling System Validation
The degree of cleanliness of air in the pharmaceutical manufacturing and related
operation area should be established depending on the characteristics of products
and operations in the area. In order to establish and maintain such standards,
careful attention has to be exercised to keep the standards from the stage of design
and construction through to the monitoring in the stage of routine operations.
A total air handling system, covering the open air intake, treatment, the
supply to the manufacturing area, and the exhaust, should be designed and validated.
The handling system contains units of prefiltration, temperature and humidity
control, final air filtration, return, and exhaust. When the air is supplied
to the manufacturing area, care is required in maintaining the required air quality
during the operation or at the point of product exposure to the environment.
This point is closely related to the layout and construction features of the manufacturing
area.
1. The air must flow from the critical or most clean area to the surrounding
area; that is, the less clean area. For this purpose, rooms used for
the manufacturing operation have to be laid out according to the order
of the required air cleanliness.
2. In order to maintain the air cleanliness in the area and airflow, the
amount of air supplied and exhaust have to be balanced to keep the
designed air exchange ratio, airflow pattern, and air pressure differentials.
In each room the operation site should be maintained in the
most suitable status. For such purposes, the following items must be
carefully controlled:
Copyright © 2003 Marcel Dekker, Inc.
a. Locations and number of air supplies
b. Locations and number of air exhausts
c. Ratio of air exchange
d. Return ratio of exhaust air
e. Location of local air exhaust, if necessary
f. Airflow pattern at the site of product exposure
g. Air velocity at the point of product exposure
These features have to be well designed, installed, validated, and maintained.
Critical operation has to be performed under the unidirectional airflow
(laminar airflow). Air turbulence deteriorates air quality by intake of air from
the surrounding less clean areas.
The amount of air supplied and exhausted is related to the air pressure
differentials. After the system is validated, air quality should be continuously
monitored and maintained during manufacturing operations.
Filters used for the prefiltration and final filtration should be maintained
to operate to their design specifications. Deterioration of filters is caused by
leakage and/or accumulation of particles. The former is tested by periodical
integrity test (usually dioctylphthalate DOP test), and the latter is tested by the
increase of air pressure differentials between the upstream and downstream sides
of the filter.
C. Validation of Air Handling Systems
All of the environmentally-controlled areas of pharmaceutical manufacturing
and its related areas should meet the requirement of air cleanliness, which is
expressed as classifications specified by official standards, such as ISO (International
Organization of Standardization) or FED-STD (U.S. federal standard)
209, and/or GMP. The classification has a close relationship with the air treatment
procedures and construction features.
1. First of all, the most suitable quality grade of air for the manufacturing
environment, and operation performed has to be selected.
2. Second, the air handling system/method that suits the facility and
combination of equipment has to be designed. Therefore, design qualification
is the first step of the validation.
3. Before completing construction of the air handling system, the constructed
system has to be scrutinized as to whether or not it is built
according to the design.
4. After confirming the installation of facility and equipment, the quality
of air is examined from various viewpoints according to the predetermined
specifications.
5. In the routine operation, representative quality items have to be moni-
Copyright © 2003 Marcel Dekker, Inc.
tored to confirm the performance of normal operation, and if any
undesirable trends or out of specification results are found, corrective
action should be taken. These processes of checking design and construction,
confirmation of proper installation and operation, and documentation
of these processes are termed qualification/validation.
6. In case of system change or any changes of equipment, the same
procedure should be taken. These processes are summarized as follows:
a. Selection of air quality
b. Determination of air handling system and design of the construction
features
c. Construction and qualification of installation
d. Test run and operational qualification
e. Operation of air handling system and confirmation of the air quality;
that is, qualification of operation, and monitoring of operations;
that is, operational qualification
f. Revalidation, or change control [9,10,12]
D. Classification of Air Quality and Design Qualification
1. Establishment of Clean Room Classifications
The design and construction of clean rooms and controlled environments are
specified in USP, FED-STD 209E, and ISO air cleanliness standards. The cleanliness
classifications are defined by the absolute concentration of airborne particles.
Methods used for the assignment of air classification of controlled environments
and for monitoring airborne particulates are included in these standards.
FED-STD 209E or ISO standards of air cleanliness and controlled environments
are used by pharmaceutical manufacturers to provide specifications for clean
rooms and the commissioning and maintenance of these facilities. Data available
in the pharmaceutical industry, however, provide no scientific agreement on a
relationship between the number of nonviable particulates and the concentration
of viable micro-organisms. Nevertheless, the rationale that the fewer particulates
present in a clean room the less likely it is that airborne micro-organisms will
be present is accepted and can provide pharmaceutical manufacturers and builders
of clean rooms and other controlled environments with engineering standards
in establishing a properly functioning facility.
As applied in the pharmaceutical industry, FED-STD 209E and ISO Air
Cleanliness Standards are based on limits of all particles with sizes equal to or
larger than 0.5 µm. Table 2 describes airborne particulate cleanliness classes
in federal standard 209E and ISO air cleanliness standards as adapted to the
pharmaceutical industry. It is generally accepted that if fewer particulates are
Copyright © 2003 Marcel Dekker, Inc.
Table 2 Air Quality Classification and Concentrations of Controlled Environment
U.S. EEC/CGMP
Particles per Particles per m3 ISO classification of 209E USP 209E (1989)/WHO
m3 >0.1 µm  0.5 µm airborne particulates (1992) customary GMP
— 1.00 —
102 3.50 ISO class 2 — — —
— 1.00 — M1 — —
103 35.30 ISO class 3 M1.5 1 —
— 102 — M2 —
104 3.53 ? 102 ISO class 4 M2.5 10 —
— 103 — M3 — —
105 3.53 ? 103 ISO class 5 M3.5 102 A&B
— 104 — M4 — —
106 3.53 ? 104 ISO class 6 M4.5 103 —
— 105 — M5 — —
107 3.53 ? 105 ISO class 7 M5.5 104 C
— 106 — M6 — —
108 3.53 ? 106 ISO class 8 M6.5 105 D
— 107 — M7 —
Source: Refs. 15, 19.
present in an operational clean room or other controlled environment, the less
the microbial count under operational conditions.
Clean rooms are maintained under a state of operational control on the
basis of dynamic (operational) data. Class limits are given for each class name.
The limits designate specific concentrations (particles per unit volume) of airborne
particles with sizes equal to and larger than the particle sizes shown in
Table 2 [7,10–12,14].
Air quality relating to the manufacturing of sterile pharmaceutical products
is designated in WHO and EU GMP as A, B, C, and D, and in USP as
class 100, class 10,000, and class 100,000. These classes correspond to ISO
class 5, ISO class 7, and ISO class 8, respectively (there is no class corresponding
to B grade in FDA/USP) [13–19].
2. ISO Classification of Air Cleanliness
The ISO air cleanliness level (class) is expressed in terms of an ISO air classification
number (class N). This represents the maximum allowable concentrations
(in particles/quantity of air) for considered sizes of particles [18,19]. The concentrations
are determined by using the formula given below.
Copyright © 2003 Marcel Dekker, Inc.
Airborne particulate cleanliness shall be designated by a classification
number N. The maximum permitted concentration of particles Cn for each considered
particle size D is determined from the formula
Cn = 10N ? 
 0.1
D 2.08
where
Cn represents the maximum permitted concentration (in particles/m3 of
air) of airborne particles that are equal to or larger than the considered
particle size. Cn is rounded to the nearest whole number, using no
more than three significant figures.
N is the ISO classification number, which shall not exceed a value of 9.
D is the considered particle size in µm.
0.1 is a constant with a dimension of µm.
Figure 6 presents relationships between sizes of airborne particulates and
concentrations in each ISO air cleanliness class. The relationship between the
requirement for air cleanliness and manufacturing operation is summarized in
Table 3.
Aseptic processing and processes related to sterile products manufacturing
should be carried out in the environment of the area under the defined air
quality.
Airflow should also be designed, validated, and confirmed to be maintained
as such by the monitoring of air quality. There are no official requirements
for the manufacturing of nonsterile products; however, air quality and
airflow should be designed, validated, and monitored for the purpose of preventing
contamination.
E. Unidirectional Airflow (Laminar Flow)
Control Equipment
Area A (class 100, ISO class 5), which applies to air handling equipment at the
filling line and microbiological testing area, shall provide HEPA-filtered laminar-
flow air. (Note: The term laminar flow has not been used recently; instead
the term “unidirectional air flow” is used [FED-STD-209E, Sept. 11, 1992].
Unidirectional airflow [referred to as laminar airflow] is an airflow having generally
parallel streamlines, operating in a single direction, and with uniform
velocity over its cross section [15,19].
Such equipment shall
Copyright © 2003 Marcel Dekker, Inc.
ISO class 9
ISO class 8
ISO class 7
ISO class 6
ISO class 5
ISO class 4
ISO class 3
ISO class 2
ISO class 1
Figure6 ISO classification of airborne particulate cleanliness. (From Ref. 19.)
1. Have hood or airflow direction panels and working surface areas that
are constructed of a smooth, durable, nonflaking material, such as
glass, plastic, or stainless steel.
2. Have prefilters that are disposable or fabricated from a material that
can be properly cleaned and reused.
3. Have HEPA final filters that have been tested to assure leak-proof
construction and installation.
4. Provide a laminar airflow with an average velocity of 90 ft per min
over the entire air exit area. The air velocity should be high enough
to maintain the unidirectional flow pattern.
5. Be monitored according to a written program and scheduled for compliance
with the requirements.
Schematic construction features for an aseptic processing area are shown
in Figure 7.
Copyright © 2003 Marcel Dekker, Inc.
Table 3 Air Quality Classification and Process Step
Products for European supply
Terminally sterilized
Typical process step Not unusually at risk Unusually at risk Aseptically processed
Dispensing Grade D Grade C (controlled) Grade C (controlled)a
Compounding Grade D Grade C (controlled) Grade C (controlled)a
Filtration From grade D to From grade C (con- From grade C (congrade
C (controlled) trolled) to grade A trolled) to grade A
(critical) or closed (critical) [backsystems
ground grade B
(clean)] or closed
systems
Container prep/wash + Grade D Grade C (controlled) Grade D
stopper prep/wash
Container sterilization From grade D to From grade C (con- From grade D to
Depryogenation grade C (controlled) trolled) to grade A grade A (critical)
(critical)
Stopper Sterilization From grade D to From grade C (con- From grade D to
grade C (controlled) trolled) to grade A grade A (critical)
(critical)
Filling and stoppering Grade C (controlled) Grade A (critical) Grade A (critical)
[background grade [background grade
C (controlled)] B (clean)]
Lyophilization — — Grade A (critical)
[background grade
B (clean)]
Note. Capping and crimping, terminal sterilization, inspection and labeling and packaging “pharmaceuticals.”
aFor European aseptically produced products with sterile raw materials, where sterile filteration is not carried out,
then dispensing and compounding shall be in a grade A area, with a grade B background.
Source: Refs. 14, 20.
F. Performance Qualification and Parameters
of Cleanliness
A controlled environment such as a clean zone or clean room is defined by
certification according to a relevant clean room operational standard. Parameters
that are evaluated include
1. Number of airborne particles
2. Number of airborne microbes
3. Filter integrity, including HEPA filter leak test
Copyright © 2003 Marcel Dekker, Inc.
Figure 7 Major construction features for aseptic processing. (From Ref. 12.)
4. Air velocity
5. Airflow patterns
6. Air changes ratio
7. Pressure differentials
These parameters can affect the microbiological bioburden of the clean room.
Proper testing and optimization of the physical characteristics of the clean room
or controlled environment is essential prior to completion of the validation of
the microbiological monitoring program. Assurance that the controlled environment
is operating adequately and according to its engineering specifications will
give a higher assurance that the bioburden of the environment will be appropriate
for aseptic processing.
G. Microbiological Evaluation Program for
Controlled Environments
Airborne micro-organisms are not free-floating or single cells, but they frequently
associate with particles of 10 to 20 µm. Particulate counts as well as
microbial counts within controlled environments vary with the sampling location
and the activities being conducted during sampling.
Microbial monitoring programs for controlled environments should assess
the effectiveness of cleaning and sanitization practices by and of personnel that
Copyright © 2003 Marcel Dekker, Inc.
could have an impact on the bioburden of the controlled environment. Microbial
monitoring will not quantitate all microbial contaminants present in these controlled
environments. Routine microbial monitoring should provide sufficient
information to ascertain that the controlled environment is operating within an
adequate state of control, however.
Environmental microbial monitoring and analysis of data by qualified personnel
will permit the status of control to be maintained in clean rooms and
other controlled environments. The environment should be sampled during normal
operations to allow for the collection of meaningful data. Microbial sampling
should occur when materials are in the area, processing activities are ongoing,
and a full complement of operating personnel is on site.
When appropriate, microbial monitoring of clean rooms and some other
controlled environments should include quantitation of the microbial content of
room air, compressor air that entered the critical area, surfaces, equipment, sanitization
containers, floors, walls, and personnel garments (e.g., gowns and gloves).
The objective of the microbial monitoring program is to obtain representative
estimates of the bioburden of the environment. When data are compiled and
analyzed, any trends should be evaluated by trained personnel. While it is important
to review environmental results on the basis of recommended and specified
frequency, it is also critical to review results over extended periods to determine
whether or not trends are present. Trends can be visualized through the
construction of statistical control charts that include alert and action levels. The
microbial control of controlled environments can be assessed in part on the basis
of these trend data. Periodic reports or summaries should be issued to alert the
responsible manager [13].
H. Training of Personnel
The major source of microbial contamination of controlled environments is personnel.
Since the major threat of contamination of product being aseptically
processed comes from the operating personnel, the control of microbial contamination
associated with these personnel is one of the most important elements of
the environmental control program. Personnel training should be conducted before
the qualification and validation practice [13].
I. Sampling and Test of Air Quality
1. Critical Factors Involved in the Design and Implementation
of a Microbiological Environmental Control Program
An environmental control program should be capable of detecting an adverse
drift in microbiological conditions in a timely manner that would allow for
meaningful and effective corrective actions. An appropriate environmental control
program should include identification and evaluation of sampling sites and
validation of methods for microbiological sampling of the environment.
Copyright © 2003 Marcel Dekker, Inc.
2. Establishment of Sampling Plans and Sites
During initial start-up or commissioning of a clean room or other controlled
environment, specific locations for air and surface sampling should be determined.
1. Consideration should be given to the proximity to the product and
whether or not the air and surfaces might be in contact with a product
or sensitive surfaces of container closure systems. Such areas should
be considered critical areas requiring more monitoring than non-product-
contact areas.
2. The frequency of sampling will depend on the criticality of specified
sites and the subsequent treatment received by the product after it has
been aseptically processed. Table 4 shows suggested frequencies of
sampling in decreasing order of frequency of sampling and in relation
to the criticality of the area of the controlled environment being sampled.
The sampling plans should be dynamic, with monitoring frequencies
and sample plan locations adjusted based on trending performance.
It is appropriate to increase or decrease sampling based on
this performance.
3. Sampling Method by ISO Air Cleanliness Standards
Establishment of Air Sampling Locations. Derive the minimum number
of sampling point locations from the formula
NL = vA
where
NL is the minimum number of sampling locations (rounded to a whole
number).
Table 4 Suggested Frequencies of Sampling on the Basis of Criticality of
Controlled Environment
Sampling area Frequency
Class 100 or better room Each operating shift
Supporting areas adjacent to class 100 Each operating shift
Other support areas (class 100,000) Twice/week
Potential product/container contact areas Twice/week
Other support areas to aseptic processing
Areas but nonproduct contact (Class 100,000 or lower) Once/week
Source: Ref. 13.
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A is the area of the clean room of clean air controlled space in m2. In
the case of unidirectional perpendicular airflow, the area A may be
considered as the cross section of air horizontal to the airflow.
It should be ensured that the sampling locations are evenly distributed
throughout the area of the clean room or clean zone and positioned at the height
of the work activity.
4. Establishment of Single Sample Volume Per Location
Sample a sufficient volume of air at each location that a minimum of 20 particles
would be detected if the particle concentration for the relevant class were
at the class limit for the largest considered particle size.
The single sample volume VS per location is determined by using the
formula
VS =
20
Cn,m
? 1000
where
VS is the minimum single sample volume per location, expressed in
liters.
Cn,m is the class limit (number of particles/m3) for the largest considered
particle size specified for the relevant class.
20 is the defined number of particles that could be counted if the particle
concentration were at the class limit.
When VS is very large, the time required for sampling can be substantial. By
using the sequential sampling procedure both the required sample volume and
the time required to obtain samples may be reduced.
The sampling probe shall be positioned pointing into the airflow. If the
direction of the airflow being sampled is not controlled or predictable (e.g.,
nonunidirectional airflow), the inlet of the sampling probe shall be directed vertically
upward. At a minimum, sample the above-determined volume of air at
each sampling location.
5. Interpretation of Results by ISO Air Cleanliness Standard
The clean room or clean zone is deemed to have met the specified air cleanliness
classification if the averages of the particle concentrations measured at each of
the locations and, when applicable, the 95% upper confidence limit, do not
exceed the concentration limits required [13,15,19].
Copyright © 2003 Marcel Dekker, Inc.
J. Continuous Automatic Monitoring of Air
Continuous automatic air monitoring for multipoints can provide much more
information about the environment. Using the statistical analysis of the data
obtained by the continuous multipoints monitoring is the best method to monitor
the air cleanliness and to take necessary actions before the data exceed an alert
level or an action level. The method has many advantages over the data obtained
by discrete monitoring methods.
In the continuous automatic monitoring of the air quality, in which a remote
probe is used, it must be determined that the extra tubing does not have an adverse
effect on the viable airborne count. This effect should either be eliminated, or if
this is not possible, a correction factor should be introduced in reporting the results.
The number of sampling ports should be calculated according to the formula
described previously, and sampling ports should be located as mentioned above.
In addition to the specified number of sampling ports, sampling ports should be
placed at the critical positions by considering the nature of the operation.
By applying this kind of continuous monitoring system, we can always
know the real-time state of air cleanliness and its trend [12]. This also affords
information as to the state of integrity of the HEPA filter without waiting for
the result of a DOP integrity test (usually performed every 6 months). A schematic
drawing of a continuous automatic air sampler is shown in Figure 8. An
example of monitoring data is shown in Figure 9.
K. Establishment of Microbiological Alert and Action
Levels in Controlled Environments
The principles and concepts of statistical process control are useful in establishing
alert and action levels and in reacting to trends. An alert level in microbiological
environmental monitoring is that level of micro-organism that shows a
potential drift from normal operating conditions. Exceeding the alert level is not
necessarily grounds for definitive corrective action, but it should at least prompt
a documented follow-up investigation that could include sampling plan modifications.
An action level in microbiological environmental monitoring is the level
of micro-organism that when exceeded requires immediate follow-up and, if
necessary, corrective action.
Initially alert levels are established based upon the result of PQ, and reviewed
based on the historical information gained from the routine operation of
the process in a specific controlled environment.
Trends that show a deterioration in environmental quality require attention
in determining the assignable cause and in instituting a corrective action plan
to bring the conditions back to the expected ranges. An investigation should be
implemented, however, and the potential impact should be evaluated. Although
there is no direct relationship established between the 209E or ISO air cleanliness
standard controlled environment classes and microbiological levels, the pharma-
Copyright © 2003 Marcel Dekker, Inc.
Figure8 Schematic drawing of continuous automatic air monitoring system.
ceutical industry has been using microbial levels corresponding to air cleanliness
classes for a number of years, and these levels (shown in Table 5) have been
specified in various official compendia for evaluation of current GMP compliance
[13–16,19].
L. Methodology and Instrumentation for Quantitation of
Viable Airborne Micro-Organisms
It is generally accepted that airborne micro-organisms in controlled environments
can influence the microbiological quality of the intermediate or final
products manufactured in these areas. Also, it is generally accepted that estimation
of the airborne micro-organisms can be affected by instruments and procedures
used to perform these assays.
The most commonly used samplers in the pharmaceutical and medical
device industry are impaction and centrifugal samplers. The selection, appropriateness,
and adequacy of using any particular sampler is the responsibility of
the user.
Copyright © 2003 Marcel Dekker, Inc.
Figure9 Output example of continuous airborne particle measurement system.
1. Slit-to-agar air sampler (STA). This sampler is the instrument upon
which the microbial guidelines given in Table 3 for the various controlled
environments are based. The unit is powered by an attached
source of controllable vacuum. The air intake is obtained through a
standardized slit below which is placed a slowly revolving petri dish
containing a nutrient agar. Particles in the air that have sufficient mass
impact on the agar surface and viable organisms are allowed to grow
out. A remote air intake is often used to minimize disturbance of the
laminar flow field.
2. Sieve impactor. This apparatus consists of a container designed to
accommodate a petri dish containing a nutrient agar. The cover of the
unit is perforated, with the perforations of a predetermined size. A
vacuum pump draws a known volume of air through the cover, and
the particles in the air containing micro-organisms impact on the agar
medium in the petri dish. Some samplers are available with a cascaded
series of containers containing perforations of decreasing size.
Copyright © 2003 Marcel Dekker, Inc.
Table 5 Comparison of Numbers of Viable Organisms Allowed by EU GMP Directive and USP Chapter <1116>
Settle plates, (cfu per
Class Air (CFU per m3) Surfaces (dfu per contact plate) 4 hr; 90 mm)
EU USP USP
(grade) ISO air class customary EU USP EU (55 m) (24–30 cm2) EU USP Descriptive
A ISO class 5 100 M 3.5 <1 3 <1 3 <1 — Criticala–c
B ISO class 5 100 M 3.5 10 — 5 — 5 —
C ISO class 7 10,000 M 100 20 25 5 (floor:10) 50 — Clean
5.5
D ISO class 8 100,000 M 200 100 50 — 50 — Controlledc, non-
6.5 sterile, support
area
aRef. 13.
bRef. 14.
cAseptic Processing of Health Care Product—Part 1, General—ISO 13408-1, International Organization for Standardization, Geneva (1998).
Copyright © 2003 Marcel Dekker, Inc.
These units allow for the determination of the distribution of the size
ranges of particles containing viable micro-organisms, based on which
size perforations admit the particles onto the agar plates.
3. Centrifugal sampler. The unit consists of a propeller or turbine that
pulls a known volume of air into the unit and then propels the air
outward to impact on a tangentially placed nutrient agar strip set on
a flexible plastic base.
4. Surface air system sampler. This integrated unit consists of an entry
section that accommodates an agar contact plate. Immediately behind
the contact plate is a motor and turbine that pull air through the unit’s
perforated cover over the agar contact plate and beyond the motor,
where it is exhausted. Multiple mounted assemblies are also available.
5. Gelatin filter sampler. The unit consists of a vacuum pump with an
extension hose terminating in a filter holder that can be located remotely
in the critical space. The filter consists of random fibers of
gelatin capable of retaining airborne micro-organisms. After a specified
exposure time, the filter is aseptically removed and dissolved in
an appropriate diluent and then plated on an appropriate agar medium
to establish its microbial content.
6. Settling plates. This method is still widely used as a simple and
inexpensive way to quantitatively assess the environments over prolonged
exposure times. The exposure of open agar-filled petri dishes
or settling plates are not to be used for quantitative estimations of the
microbial contamination levels of critical environments.
One of the major limitations of mechanical air samplers is the limitation
in sample size of the air being sampled. Where the microbial level in the air of
a controlled environment is expected to contain not more than 3 cfu per cubic
meter, several cubic meters of air should be tested if the results are to be assigned
a reasonable level of precision and accuracy. Often this is not practical.
For example, slit-to-agar samplers have an 80-L-per-min sampling capacity. If
1 cubic meter of air is tested, then it would require an exposure time of 15 min.
It may be necessary to use sampling times in excess of 15 min to obtain a
representative environmental sample. Although there are samplers capable of
very high sampling volume rates, consideration in these situations should be
given to the potential for disruption of the airflow patterns in any critical area
or to the creation of a turbulence that could increase the probability of contamination.
For centrifugal air samplers, a number of earlier studies showed that the
samples demonstrated a selectivity for larger particles. The use of this type of
sampler may have resulted in higher airborne counts than the other types of air
samplers because of the inherent selectivity. When selecting a centrifugal sampler,
the effect of the sampler on the linearity of the airflow in the controlled
zone where it is placed for sampling should be taken into consideration [13].
Copyright © 2003 Marcel Dekker, Inc.
M. Operational Evaluation of the Microbiological Status of
Aseptically Filled Products in Clean Rooms and Other
Controlled Environments
The controlled environment is monitored according to an appropriate environmental
monitoring program. Additional information on the evaluation of microbiological
status can be obtained by the use of media fills. Medial fills should
be considered as a method of simulating process operations by using media,
however. Therefore, the method shows not only the environmental conditions
but also operation conditions, such as the operators’ trained level, the belt speed,
and the size (opening) of vials, which have a closer relationship with the results
of media fill test. In addition, attention has to be paid to the fact that the method
is less sensitive than other monitoring methods and can only detect contaminated
products to a level of 0.1% of falling microbes. Most of the contamination detected
by media fills are caused by process troubles such as intervention of personnel or
mechanical accident rather than the environment status or air cleanliness. The
media fill test is therefore appropriate for the evaluation of overall operations, but
not appropriate to evaluate the environment or air cleanliness [12,13].
N. An Application of Technologies for Localization of
Aseptic Processing
It is easily understood that if the aseptic operation is performed in a separated
small space from which personnel have been completely excluded, the necessity
for room classification based on particulate and environmental microbiological
monitoring requirements may be significantly reduced. In other words, critical
operations in an aseptic area should be performed in the smallest space, and
intervention by personnel should be minimized by indirect means through the
use of protective glove ports and/or half suits. Application of these methods can
minimize the chance of contamination. Following are such systems currently in
place to reduce the contamination rate in aseptic processing.
1. Barriers
In the context of aseptic processing systems, a barrier is a device that restricts
contact between operators and the aseptic field enclosed within the barrier. Barriers
may not be sterilized and do not always have transfer systems that allow
the passage of materials into or out of the system without exposure to the surrounding
environment. Barriers range from plastic curtains around the critical
production zones to rigid enclosures found on modern aseptic-filling equipment.
Barriers may also incorporate such elements as glove ports, half suits, and rapidtransfer
ports.
Copyright © 2003 Marcel Dekker, Inc.
2. Isolator
This technology is used for a dual purpose. One is to protect the product from
contamination from the environment and/or personnel during filling and closing
operation by keeping the air pressure inside the isolator positive, and the other
is to protect personnel or other products from deleterious or toxic products that
are being manufactured by keeping the air pressure inside the isolator negative.
Isolator technology is based on the principle of placing previously sterilized
components (containers/products/closures) into a sterile environment.
These components remain sterile during the whole processing operation, since
no personnel or nonsterile components are brought into the isolator. The isolator
barrier is an absolute barrier that does not allow for interchanges between the
protected and unprotected environments. Isolators either may be physically
sealed against the entry of external contamination or may be effectively sealed
by the application of continuous overpressure. Manipulations of materials by
personnel are done via the use of gloves, half suits, or full suits. All air entering
the isolator passes through either a HEPA or an UPLA filter, and exhaust air
typically exits through a HEPA-grade filter. Per-acetic acid and/or hydrogen
peroxide vapor are commonly used for the surface sterilization of the isolator
unit’s internal environment. Since barrier systems are designed to reduce human
intervention to a minimum, remote sampling systems should be used in lieu of
personnel intervention. In general, once the validation establishes the effectiveness
of the barrier system, the frequency of sampling to monitor the microbiological
status of the aseptic processing area can be reduced, as compared to the
frequency of sampling of classic aseptic processing systems.
Continuous total particulate monitoring can also provide assurance that
the air filtration system within the isolator is working properly, just as in the
normal environmentally controlled area [13].
3. Summary of Air Handling Systems Validation
1. Determination of required air quality
2. Design of total air treatment system
3. Supply of air to the room
a. Amount of air
b. Locations of air supply
c. Air velocity
d. Airflow pattern
e. Exchange ratio
f. Return ratio
g. Temperature and humidity
h. Amount of exhaust
i. Location of exhaust
j. Pressure differential among the rooms
Copyright © 2003 Marcel Dekker, Inc.
4. Qualification of air cleanliness
a. Frequency of air monitoring
b. Location of sampling
c. Method of evaluation
5. Qualification of design, installation, operation, and performance, including
monitoring
6. Monitoring of air quality; monitoring data should be evaluated by
comparing with the protocol and summarized as a validation document
7. Corrective actions, if necessary
8. Change control
9. Maintenance
V. THE VALIDATION REPORT
Validation reports are written at the conclusion of the equipment IQ and OQ
and when process validation is completed. The reports should be stand-alone
documents containing all pertinent information because they will serve as primary
documentation for later FDA regulatory inspections and as reference documents
when changes to the system are planned and the need for revalidation is
under consideration.
Like the validation protocol, the validation report has a standard format.
It begins with a brief executive summary, in which the major findings and recommendations
are presented. All protocol deviations are identified here, along
with a brief explanation of the reason for the deviation and its impact, if any,
on the outcome of the validation. Next is a discussion section, in which all
findings, conclusions, and recommendations noted in the executive summary are
explained in detail. Topics should be presented in the order in which they appear
in the protocol. Protocol deviations are fully explained and justified, and a judgment
is made by a competent individual (or individuals) regarding their impact on
the validation study. Data tables and attachments should be referenced as needed.
Conclusions and recommendations is the next section. Here, a statement
is made regarding the validation status of the water or air treatment system and
the possible need for additional validation studies focusing on some aspect or
component of the system.
The last section of the report is a list of attachments. Because the report
will be the official, complete file on the water or air treatment system validation,
it must contain raw data, drawings, manuals, tables, instrument calibration reports,
and a copy of the validation protocol along with any protocol addenda.
The report is then endorsed and dated by designated representatives of each unit
involved in the water or air treatment system validation.
Copyright © 2003 Marcel Dekker, Inc.
REFERENCES
1. ICH. Good Manufacturing Practice Guide for Active Pharmaceutical Ingredients.
Q7A (March 15, 2000).
2. General information (1231): Water for pharmaceutical purposes. U.S. Pharmacopeia.
vol. 25. Rockville, MD: U.S. Pharmacopeial Convention, pp. 2261–2270 (2002).
3. Water for injection, purified, sterile. U.S. Pharmacopeia. vol. 25. Rockville, MD:
pp. 1809–1890 (2002).
4. Purified water, water for injection. European Pharmacopeia. 3rd ed. Strasbourg:
European Pharmacopeia Convention, pp. 1723–1724 (1996).
5. Water for injection. Japanese Pharmacopeia. 14th ed. Tokyo: Hirokawa, p. D-751
(2001).
6. Meltzer, T. H. Pharmaceutical Water Systems. Littleton, CO: Tall Oaks, p. 683–
691 (1996).
7. FDA. FDA’s proposed current good manufacturing practices (GMP) for regs. for
large volume parenterals (LVP). Fed Reg (June 1, 1976). Preliminary Concept Paper
of Sterile Drug Products Produced by Aseptic Processing, draft paper, Sept. 27, 2002.
8. Carton, F. J., Agalloco, J. P., Artiss, D. H. Validation of Aseptic Pharmaceutical
Process: Water System Validation. New York: Marcel Dekker (1996).
9. Pharmaceutical Engineering Guide Vol. 4: Water and Steam Guide. Tampa, FL:
ISPE, (1997).
10. Code of Federal Regulation Title 21, Part 211. Current good manufacturing practice
for finished pharmaceuticals (2002).
11. Cleaning and Cleaning Validation: A Biotechnology Perspective. Bethesda, MD:
PDA (1996).
12. Kawamura, K. Scale-up, validation and manufacturing of microspheres in the “sustained
release injectable products.” J. Senior and M. Radomsky, eds. Englewood,
CO: InterPharm Press (2000).
13. General information <1116>: Microbiological evaluation of clean rooms and other
controlled environments. U.S. Pharmacopeia. vol. 25. Rockville, MD: U.S. Pharmacopeial
Convention, p. 2206–2212 (2002).
14. EU. GMP annex: Manufacturing of sterile products (1996).
15. Federal Standard 209E. Airborne Particulate Cleanliness Classes in Cleanroom and
Clean Zone (Sept. 11, 1992).
16. Japanese Pharmacopeia. 14th ed. suppl. Tokyo: Hirokawa (2001).
17. Pharmaceutical Engineering Guide Vol. 3: Sterile Manufacturing Facilities.
Tampa, FL: ISPE, (1997).
18. FDA/ISPE. Pharmaceutical Engineering Guide. vol. 1. Tampa, FL.
19. Classification of Airborne Particulates, in Cleanrooms and Associated Controlled
Environments—Part 1, ISO 14644-1, Geneva: International Organization for Standardization
(1999).
20. WHO GMP. Good Practices in Manufacturing of Pharmaceutical Products in
WHO Expert Committee on Specifications for Pharmaceutical Preparations, 32
edition, Geneva (1992).
Copyright © 2003 Marcel Dekker, Inc.
13
Equipment and
Facility Qualification
Thomas L. Peither
PECON—Peither Consulting, Schopfheim, Germany
I. INTRODUCTION
The importance of the qualification process of technical systems in the pharmaceutical
industry has been steadily increasing over the last 10 years. It has been
driven primarily by the requirements of regulatory bodies and not by the need
to save money in this part of the industry. If the industry made use of the full
scope of the GMP requirements, the qualification process would be more efficient
and the cost of qualification would drop. On the other hand, pharmaceutical
companies want to protect themselves from a less than perfect result during
a regulatory inspection and therefore demand 120% effort from their suppliers
and service companies. New methods and tools must be implemented to reach
the goal of qualifying a technical system while minimizing effort.
Another aspect is the trend for quality assurance departments to evolve
from being mere controllers of product quality to delivering tools and methods
to other departments, thus helping them to design a better production process.
The goal is to improve overall production reliability and availability. In order
to achieve this objective, the quality assurance team must be experienced in
applying and teaching the qualification tools and methods needed. This is a
trend that has not yet started in many companies. It may be seen in other industries
that more instruments and quality tools are necessary than those limited to
qualification and validation. Qualification and validation only appear to be the
beginning of a continuous development process in the quality assurance of the
pharmaceutical industry.
Copyright © 2003 Marcel Dekker, Inc.
To avoid misunderstanding, it is crucial to use the correct terms and expressions
during quality management. A list of definitions can be found in the
appropriate section.
The following describes how the qualification of pharmaceutical equipment
and facilities can be efficiently planned and executed.
Figure 1 depicts the most commonly used approach to the qualification
process as used in the pharmaceutical industry. It shows a pyramid, which is
the best way in which to plan a qualification/validation project. Investing more
time in the first phases will save time and money in later and critical phases. If
inadequate investment is made during the start-up of a project, the later phases
of installation qualification (IQ), operational qualification (OQ), and performance
qualification (PQ) will necessarily require an inordinate amount of time
and money. The project will be a pyramid again, but now it is inverted.
It must be stressed that a good engineering and project process is the best
basis for proper qualification and validation work. It is the current opinion on
qualification in the pharmaceutical industry that the later steps in the qualification
process need more time and attention than the earlier steps. This may be
totally different in other industry branches; they tend to spend more effort during
the earlier stages to save time and money later on.
Figure 1 Steps of qualification.
Copyright © 2003 Marcel Dekker, Inc.
If the pharmaceutical industry adopted the lessons learned in other
branches (e.g., aircraft industry, automotive industry) it could realize an increased
efficiency in the qualification and validation processes. To this end effort
should be made to investigate statistical process control (SPC), house of
quality, Deming circuits, and so on.
At the moment the term design qualification (DQ) is the focus of some
controversy. Performing a DQ is not a legal requirement, but it has been introduced
to the qualification process through implementation of Annex 15 to the
EC Guide on Good Manufacturing Practices for Medical Products. It is not a
requirement to implement a DQ, but it seems that regulatory bodies have an
interest in promoting this element of engineering and quality management. It
should be a requirement of a proper engineering process, and in fact although it
is often a part of the engineering process, it is not declared as a separate action.
Nevertheless, the activity itself should be executed in combination with an efficient
procedure documented in a standard operating procedure (SOP). (See Sec.
V.) Important aspects that should be taken into consideration before qualification
aspects start are shown in Figure 2.
It is important to perform these preliminary steps conscientiously. Most
qualification projects fail because these basic activities are not performed adequately.
Figure 2 Preliminary steps.
Copyright © 2003 Marcel Dekker, Inc.
II. PROJECT MANAGEMENT
Good project management is the first step toward organizing the successful
qualification of a technical system. A well-structured and -planned approach to
qualification is the first step toward success.
The tools and methods of project management are mainly used for large
and complex projects. It is equally important to apply these management skills
to smaller projects, however. A good project start is the best way to win the
battle.
A. Project Organization
To start with, the project organization must be defined. The different positions
must be defined and people need to be found with the necessary knowledge to
fill these positions. The most commonly required areas of expertise for a project
leader are organizational know-how, social skills, project management knowhow,
time management, validation know-how, and general technical know-how.
A team member should have expertise in communication skills, validation
know-how, and detailed technical know-how.
B. Meeting Management
The communication structure must be defined following the definition of the
best project organization. A lot of projects waste time in meetings. Everybody
is familiar with this scenario. You find yourself sitting in a meeting thinking
that your time is being wasted and that you might not attend another scheduled
meeting. Nobody likes to feel that his or her time is wasted, therefore thorough
planning prior to any meeting is mandatory.
A chairperson heading the meeting must be chosen and a person designated
to take the minutes. Every meeting should have an agenda. People should
be invited based on whether or not they can help with solving the issues on the
agenda. Obviously everyone attending should be well prepared. In order to facilitate
this process, meetings should be planned 6 months in advance.
C. Project Planning
After the definition of functions, responsibilities, and communication structures,
the project itself must be planned. Using Gantt charts is often the best way to
schedule the different tasks. This allows you to see quickly which task has to
be done when and by whom. The charts also indicate interdependencies between
different tasks and show what happens if a task takes longer than planned. Dif-
Copyright © 2003 Marcel Dekker, Inc.
ferent software is available to help generate such project plans. An example for
a project plan is shown in Figure 3.
People often ask for an example of a detailed project plan. Working out a
specific project plan requires in-depth knowledge of a technical system, however.
As each system is different, Figure 3 can only show a general overview
of a project plan.
D. Project Reporting
The next important task in the process of project management is the implementation
of efficient project control. A reporting system must be put into place that
describes the current state of the project as well as the progress of the most
important tasks. Additionally, the reporting system must be able to pick up and
highlight problems within the project. A functioning reporting system is the
controlling instrument for the project manager.
E. Tools for Project Management
In order to manage a project efficiently appropriate tools must be applied. There
are several products of project management software on the market. The decision
as to which system is the best suited for a given project should include the
following aspects:
Project focus
Size of a project
Number of team members
Number of tasks in a project
Required functionality
III. VALIDATION/QUALIFICATION MASTER PLAN
It is important to draw up a summarized document that describes the whole
project. It has become common practice in the industry to develop a “validation
master plan” (VMP). This document would usually include the qualification
aspects of a project. Alternatively, a “qualification master plan” (QMP) should
be drafted. In case of a large retrospective qualification project it is beneficial
to write a separate QMP. The main point is to develop a document that includes
the most important information of the project and can be used like a project
handbook.
Copyright © 2003 Marcel Dekker, Inc.
Figure 3 Project plan.
Copyright © 2003 Marcel Dekker, Inc.
Figure 4 Structure of a validation master plan.
A. Structure of a VMP or QMP
The structure of a VMP or QMP is well documented in the PIC/S document PI
006 Recommendation on Validation Master Plan, Installation and Operational
Qualification, Non-Sterile Process Validation and Cleaning Validation. This
document is the basis for Annex 15 to the EC Guide on Good Manufacturing
Practices for Medical Products. Figure 4 displays the most commonly used
topics to be described in a VMP.
The PIC/S-document PI 006 defined the VMP as “A document providing
information on the company’s validation work programme. It should define details
of and time scale for the validation work to be performed. Responsibilities
relating to the plan should be stated.” The EC Guide on Good Manufacturing
Practices for Medical Products, Annex 15, said of the VMP: “All validation
activities should be planned. The key elements of a validation programme
should be clearly defined and documented in a validation master plan (VMP)
or equivalent documents. The VMP should be a summary document which is
brief, concise and clear.” The FDA published another interesting paper in 1995,
Copyright © 2003 Marcel Dekker, Inc.
the Guide to Inspections of Validation Documentation. This guide outlines the
basics in qualification and validation; for example, “Planning documents may
use various formats and styles, and different descriptive terms may be used such
as master validation plan, project plans, study plans, and others. Regardless of
terminology, it is important that suitable documents denote intentions in sufficient
detail.” It highlights the benefits of having an overall document such as
VMP.
To summarize, the VMP or QMP should be a brief overview of the project,
tasks, tools, resources, and methods that are going to be used during the
project. This document should be described at a very early stage of a project by
the engineering or manufacturing department of a pharmaceutical manufacturer
or service provider.
Standard operating procedures are an integral part of any VMP or QMP.
They outline rules that have to be followed during the project and provide project
members with guidelines as to which rules have to be studied before starting
work.
B. Areas of Interest
Many technical systems in a pharmaceutical production have to be validated or
qualified. The requirement for a system to be validated depends on its impact on
product quality. Whether a system is critical or not may be determined through a
risk analysis. (See Design Qualification.) Following is a list of such different
systems or clusters of systems.
1. Infrastructure and Facilities
High purity water systems (high purity water, water for injection, highly
purified water, etc.)
Clean steam
Gases with product contact (compressed air, nitrogen, oxygen, vacuum,
etc.)
HVAC with rooms (clean area), including lighting
2. Equipment
Closures, tanks, vessels with product contact
Machines with product contact (filling machine, washing machine, closing
machine, granulator, packaging lines, etc.)
Machines with direct impact on product quality (autoclaves, sterilizing
units, labeling system, weighing system, production control system, facility
control system, etc.)
Copyright © 2003 Marcel Dekker, Inc.
IV. USER REQUIREMENT SPECIFICATION
The goal of working out user requirement specifications (URS; Fig. 5) is to
document the needs of the manufacturing department. User requirement specifications
are always written for a technical system that should be implemented in
the production process of a pharmaceutical product. The URS is very important
for realizing a project, as many measurements refer to the URS. A well-prepared
URS is the key to a project’s success. Projects without detailed URS have a
tendency to demand lots of change later on, thus increasing cost, start-up times,
or both. Who should evaluate a URS? Best practice is a coordinated approach
among production, quality assurance, and engineering of the pharmaceutical
company. Some companies even use the services of external resources to create
a URS.
A. GMP Requirements
The key aspect of any URS is to generate a document detailing all the GMP
requirements the technical system has to fulfill. The URS is an important document
for the commissioning phase as well. Often the URS provides the basis
for an offer to the suppliers. A detailed URS will result in a better and more
competitive offer for the technical system. While evaluating a supplier, it is
important to gather as much information as possible. Without a comprehensive
URS, a pharmaceutical company cannot get a clear understanding of the supplier
and may be led to make a wrong decision.
Figure 5 Content user requirement specification (URS) design qualification.
Copyright © 2003 Marcel Dekker, Inc.
B. Technical and Economic Requirements
User requirement specifications cover more aspects than only the GMP requirement,
because the URS is not written only for the validation procedure; in fact,
a URS is a very important project document covering technical as well as economic
requirements of the technical system. Pharmaceutical manufacturing departments
not only check the GMP aspects of a system; additionally, following
good engineering practice they will review the technical and economic aspects
of a technical system. Obviously, the more experience a company gains, the
more comprehensive a URS become. Past experiences such as project faults,
inefficient technical systems, and bad commissioning can be included in a URS.
V. DESIGN QUALIFICATION (DQ)
Design qualification is more common in Europe than in the United States. There
is no legal requirement to perform a DQ. Sometimes this phase may not be
called DQ, but may instead be referred to as “design review,” “design assessment,”
and so on. The intention is important in this phase. The goal is to perform
something similar to a risk analysis and to check the design documents of a
technical system to ensure that they fulfill the user requirements. For this reason
a risk analysis—not yet commonly known in all companies—should be used.
A. Risk Analysis
The overall concept of all of the following tools is that of risk analysis or risk
assessment. Risk analysis helps to decide whether an aspect is GMP-critical or
not. The risk analysis can be performed in a formal or more informal way.
Following are two popular and import types of risk analysis. Another method,
the fault tree analysis (FTA), has recently been used in the area of computer
validation. This method is not described here, as it is a complex form of risk
analysis.
B. FMEA
FMEA is a quantitative risk analysis for complex systems (Fig. 6). As this
approach involves assessment of occurrence probabilities, detection of failures,
and judgment as to the severity of a failure, it should only be chosen if some
practical experience with the technical system is available. Each of the three
values will be assigned a number from 1 to 5. Multiplying these values results
in the “risk priority number.” This number indicates the priority of the assessed
failure. The pure version of the FMEA is seldom practiced in the pharmaceutical
industry.
Copyright © 2003 Marcel Dekker, Inc.
Figure6 Failure mode and effects analysis (FMEA) overview.
Most common risk analysis forms are mutations of the fundamental
FMEA. It is easier for most companies to start initially with a more practical
way of performing a risk analysis. In the future the fundamental FMEA will be
more commonly applied, as companies will have gained confidence with variations
of the FMEA.
Variations are often made by cutting the detection of failures or severity
of failures. Sometimes the values are decreased to a spread of 1 to 3. In other
cases the risk priority number is not calculated, but the levels are noted in a
matrix to see whether the point is critical or not.
C. Hazard Analysis of Critical Control Points (HACCP)
The second method is the hazard analysis of critical control points (HACCP;
Fig. 7). This method is well known in the food industry. The goal of HACCP
is to reduce the risk of contamination of products and to reduce the effort for
testing products during final tests. The HACCP defines critical control points
(CCPs) in different grades (usually three grades). The HACCP protocols are
Copyright © 2003 Marcel Dekker, Inc.
Figure 7 Hazard analysis of critical control points (HACCP).
worked out and the results are documented in reports. Important steps are the
definition of CCPs and their limits, the implementation of a change control system,
the execution of corrective actions, and the implementation of a documentation
system. Equally important are regular audits of the concept and the approval
of HACCP protocols using appropriate procedures. As with the FMEA, the
HACCP concept offers the opportunity to rethink all technical and organizational
aspects in an early phase of a project and to find out all critical deficiencies.
D. Documentation of DQ
The results of any risk analysis should be well documented as they become the
key input into the qualification and validation process. They are the basis for
defining tests in the IQ, OQ, and PQ phases. It is often impossible to say prior
to a risk analysis what steps of qualification need to be performed. It depends
on the risks and measurements defined during the risk analysis. Equally important,
this procedure increases the efficiency of the qualification process. In the
past, the decision on which qualification tests to perform was outlined by writing
qualification protocols. These usually prompted long and expensive discus-
Copyright © 2003 Marcel Dekker, Inc.
sions. One of the challenges is to determine which parts of a system to devise
tests for. It is easy to imagine that companies and people who have experience
with risk analysis are in a better position, as they will have developed standard
tests for a list of critical elements, leaving only a few additional tests to be
designed for a particular system. The result is that the longer the qualification
system is in place the more effective it becomes. This is a great advantage and
helps to repay the investments of starting a risk analysis system quickly.
VI. INSTALLATION QUALIFICATION
The decision as to which system needs to be qualified should result directly
from the risk analysis process and should be described in the VMP or QMP. In
any case, it would be a technical system that impacts on the quality of a pharmaceutical
product. Installation qualification aims to check documentation against
reality. The result is “as-built documentation.” The other task in the IQ is to
ensure that the GMP requirements are fulfilled. The generally accepted way to
perform an IQ is to
Develop an IQ protocol (Fig. 8)
Approve the IQ protocols (by the quality assurance, production, and technical
departments)
Perform the IQ
Work out the IQ report
Approve the IQ report (by the quality assurance, production, and technical
departments)
Installation qualification is defined in the PIC/S document PI 006 as “The
performance and documentation of tests to ensure that equipment (such as machines,
measuring equipment) used in a manufacturing process, are appropriately
selected, correctly installed and work in accordance with established specifications.”
The OQ phase relies on valid calibration of all quality-relevant instruments.
The best way to guarantee this is to perform the calibration at the end of
the IQ phase. Sometimes it is performed at the beginning of the OQ. This procedure
is acceptable as well.
The IQ phase will be executed with personnel of the supplier of a technical
system or with technical personnel of the pharmaceutical company. It will
follow the procedures set out in the IQ protocols. After performing the IQ, the
results are summarized and documented in an IQ report.
The qualification of the control unit of a technical system is very similar
to that of the mechanical equipment of a system. This does not apply to compu-
Copyright © 2003 Marcel Dekker, Inc.
Figure 8 Example of an IQ protocol.
Copyright © 2003 Marcel Dekker, Inc.
Figure8 Continued.
terized systems, however. These are described in detail in another part of this
book.
The most important aspects to consider during IQ are
Provide as-built documentation (e.g., P&ID check).
Check training reports.
Check that documentation is complete.
Check calibration reports.
Identify piping and instrumentation
VII. OPERATIONAL QUALIFICATIONS
Operational qualification is defined in the PIC/S document PI 006 as “Documented
verification that the system or sub-system performs as intended throughout
all anticipated operating ranges.”
Operational qualification tests whether or not the system works as expected.
The approach to a successful OQ is the same as described for IQ [develop
OQ protocols (Fig. 9)], approve OQ protocols (by the quality assurance,
production, and technical departments), perform OQ, work out OQ report, and
approve OQ report (by the quality assurance, production, and technical departments).
The OQ phase normally involves personnel from the supplier of a technical
system or technical personnel from the pharmaceutical company. It is prefer-
Copyright © 2003 Marcel Dekker, Inc.
Figure 9 Example of an OQ protocol.
Copyright © 2003 Marcel Dekker, Inc.
able to include customer employees, as they are going to be the users of the
system. This facilitates a better know-how transfer between supplier and customer.
Again, this process follows the rules outlined in the OQ protocols. The
results of OQ are summarized and documented in an OQ report. It is commonly
accepted practice in the industry to produce one report for both IQ and OQ
results. This saves money and time for approval.
Operational qualification of the control unit of a technical system is one
of the most important steps during the OQ phase. It tests all critical functions
and alarms of the technical system. There are no different procedures for mechanical
OQ and control unit OQ.
The result of the OQ is a documented approval that the technical system
fulfills the user requirements and all GMP-related functions of the technical
system.
Typical tests in the OQ include the following:
Alarm tests
Behavior of the system after energy breakdown
Accuracy of filling lines
Transportation speed in a sterilization tunnel
Temperature distribution in an autoclave
Performance of a washing machine
Accuracy of a weighing system
VIII. PERFORMANCE QUALIFICATION
The PQ is the phase in which either a technical system is tested over a long
period of time (e.g., water system), or a complex technical system is tested
overall (connected filling line). For many systems OQ is the last phase performed
during qualification. If there are only a few performance tests needed,
it might be more practical to include them during OQ or process validation.
Combining OQ and PQ decreases the number of documents (less documentation
work in the future) and cuts approval time and effort. Again, the procedure for
PQ is the same as for IQ and OQ ([develop PQ protocols, approve PQ protocols
(by the quality assurance, production, and technical departments), perform PQ,
work out the PQ report, and approve the PQ report (by the quality assurance,
production, and technical departments)]. The documentation and test description
are identical to those in the OQ phase.
Performance qualification should be executed by customer personnel. It is
a great disadvantage if it has to be performed by the supplier. Ideally this phase
allows know-how to be established at the pharmaceutical company.
The following technical systems need to be performance-tested and qualified:
Copyright © 2003 Marcel Dekker, Inc.
High purity water systems (monitoring of the quality parameters: pH,
TOC, conductivity, CPU, temperature)
HVAC systems (temperature, pressure, humidity)
Complex connected systems (e.g., filling line, BPI production line; performance
parameters)
IX. DOCUMENTATION SYSTEM
To quickly locate any given document, it is mandatory to have implemented an
appropriate documentation system. In case of a fault in production or inspection,
it becomes necessary to find a document within 15 to 20 min. All companies
should test the reliability of their documentation system using internal audits.
One aspect of a working documentation system is a standardized documentation
structure. If every system is documented using the same document
structure, everyone can gain access to the necessary information quickly. Figure
10 shows an example of a documentation structure.
Documents do not need to be delivered to the customer in paper format.
Electronic media documents such as CDs are equally acceptable. Obviously, an
appropriate reading system must be in place to access the documents at a later
date (e.g., for an inspection). Such a system must remain in place until the
Figure 10 Documentation structure.
Copyright © 2003 Marcel Dekker, Inc.
documentation is destroyed. In case of a complete electronic documentation
system the whole system needs to be validated by computer validation.
X. CHANGE CONTROL
Change control is defined in the PIC/S document PI 006 as follows: “A formal
system by which qualified representatives of appropriate disciplines review proposed
or actual changes that might affect a validated status. The intent is to
determine the need for action that would ensure and document that the system
is maintained in a validated state.”
Change control is a lifetime monitoring approach. Planning for wellexecuted
change control procedures (Fig. 11) includes the following aspects:
Figure 11 Change control procedure flowchart.
Copyright © 2003 Marcel Dekker, Inc.
Workable documentation system
Defined responsibilities and job descriptions
Defined review procedures
Well-trained staff
The implementation of a change control system is an important and necessary
step in the validation approach for equipment and facilities. Vital to any
change control system is its efficiency in that it does not require too much time
and effort to handle changes. In order to design an efficient change control
system, the following aspects need to be taken into consideration:
Early categorization of a change as major or minor change (i.e., catalogue).
This should speed up the decision and approval time of a
change.
Easy and logical way of document flow (production engineering, quality
assurance, production).
Easy and logical decision tree for major or minor changes or planned or
emergency changes.
It is not only good practice but also essential that a requested change is
only implemented after the appropriate change control procedures and approvals
have been followed. Time and money are often wasted because a change was
not correctly evaluated (major or minor) or personnel was not familiar with the
best practice for change control procedures. It is crucial for an efficient change
control process that the production, engineering, and validation departments are
working together very closely.
Clear change control procedures have to be in place for all eventualities.
This must include instructions for situations in which the supervisory or management
personnel is not present when the problem occurs. In such a case, for
example, a change or correction might be implemented quickly by the maintenance
or operational personnel that must then be reviewed and approved by
management within 24 hr.
REFERENCES
1. U.S. Food and Drug Administration. 21 CFR 210/211 Good Manufacturing Practice.
Fed Reg (2001).
2. U.S. Food and Drug Administration. Guide to Inspection of Validation Documentation
(1995).
3. Recommendation on Validation Master Plan, Installation and Operational Qualification,
Non-Sterile Process Validation and Cleaning Validation, Pharmaceutical Inspection
Co-Operation Scheme PIC/S PI 006 (2002).
Copyright © 2003 Marcel Dekker, Inc.
4. EC. Guide on Good Manufacturing Practices for Medical Products. EU (2001).
5. U.S. Food and Drug Administration. Guide to Inspection of Process Validation
(1987).
6. The gold sheet. F-D-C Rep 34 (2000).
7. Vina, B. GMP Compliance, Productivity, and Quality. Interpharm Press (1998).
8. ISPE. Baseline? Pharmaceutical engineering guide series: Introduction of commissioning
and qualification. ISPE 2000 European seminar, Amsterdam, 2000.
Copyright © 2003 Marcel Dekker, Inc.
14
Validation and Verification
of Cleaning Processes
William E. Hall
Hall & Pharmaceutical Associates, Inc., Kure Beach, North Carolina, U.S.A.
I. INTRODUCTION
The cleaning processes used in pharmaceutical operations have achieved an increasing
emphasis in the past decade both by the regulatory agencies and industry
itself. At this time it is generally regarded as just as critical to have effective
cleaning processes as to have consistent, validated manufacturing processes.
Several developments have caused this emphasis on the cleaning process. First,
the new generation of products (as well as those in the current “pipeline”) tend
to be more potent (e.g., many are