INJECTABLE DRUG
`DEVELOPMENT
`
`TECHNIQUES TO REDUCE
`PAIN AND IRRITATION
`
`Edited by
`
`Pramod K. Gupta
`and
`Gayle A. Brazeau
`
`Interpharm Press
`Denver, Colorado
`
`PRESS
`
`CSL EXHIBIT 1006
`CSL v. Shire
`
`Page 1 of 33
`
`

`

`Invitation to Authors
`Interpharm Press publishes books focused upon applied tech(cid:173)
`nology and regulatory affairs impacting healthcare manufactur(cid:173)
`ers worldwide. If you are considering writing or contributing to
`a book applicable to the pharmaceutical, biotechnology, medical
`device, diagnostic, cosmetic, or veterinary medicine manufacturing in(cid:173)
`dustries, please contact our director of publications.
`
`Library of Congress Cataloging-in-Publication Data
`
`Injectable drug development : techniques to reduce pain and irritation I
`edited by Pramod K. Gupta and Gayle A. Brazeau.
`p. em.
`Includes bibliographical references and index.
`ISBN 1-57491-095-7
`1. Injections. 2. Injections-Complications. 3. Drug development.
`I. Gupta, Pramod K., 1959-
`. II. Brazeau, Gayle A.
`[DNLM: 1. Injections-adverse effects. 2. Pain-chemically induced.
`3. Pain-prevention & control. 4. Pharmaceutical Preparations(cid:173)
`administration & dosage. WB 354 156 1999]
`RM169.149 1999
`615' .6-dc21
`DNLM/DLC
`for Library of Congress
`
`99-26911
`CIP
`
`10 9 8 7 6 54 3 2 1
`
`ISBN: 1-57491-095-7
`~opyright © 1999 by Interpharm Press. All rights reserved.
`·,
`f.C:>
`'<;
`'\.
`f
`p:: All ~ights reserved. This book is protected by copyright. No part of it may be re(cid:173)
`. ..
`<2.- produced, stored in a retrieval system, or transmitted in any form or by any
`mea$s, electronic, mechanical, photocopying, recording, or otherwise, without
`,r; wrttt,tm permission from the publisher. Printed in the United States of America.
`c.!:~
`'Where a product trademark, registration mark, or other protected mark is
`~ m;;1 in the text, ownership of the mark remains with the lawful owner of the
`~a ~- No claim, intentional or otherwise, is made by reference to any such marks
`m his book.
`/ While every effort has been made by Interpharm Press to ensure the accuracy
`-....__..,of the information contained in this book, this organization accepts no responsi(cid:173)
`bility for errors or omissions.
`
`,·.·.·
`\ ')
`'"-
`
`Interpharm Press
`15 Inverness Way E.
`Englewood, CO 80112-5776, USA
`
`Phone: +1-303-662-9101
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`+ 1-303-7 54-3953
`Orders/on-line catalog:
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`
`Page 2 of 33
`
`

`

`1); 1 r1!,1t
`v; r~
`~ l) t-f
`Tc;G
`
`.........._,,
`
`Contents
`
`Preface
`Acknowledgments
`
`Editors and Contributors
`
`A: BACKGROUND OF PAIN, IRRITATION, AND/OR
`MUSCLE DAMAGE WITH INJECTABLES
`
`1.
`
`Challenges in the Development of
`Injectable Products
`Michael J. Akers
`
`General Challenges
`Safety Concerns
`Microbiological and Other Contamination Challenges
`Stability Challenges
`Solubility Challenges
`Packaging Challenges
`Manufacturing Challenges
`Delivery/ Administration Challenges
`References
`
`xiii
`xiv
`
`XV
`
`3
`
`4
`5
`6
`8
`10
`11
`11
`13
`14
`
`iii
`
`Page 3 of 33
`
`

`

`iv
`
`2.
`
`Injectable Drug Development
`
`Pain, Irritation, and Tissue Damage
`with Injections
`
`Wolfgang Klement
`
`Must Injections Hurt?
`Mechanisms of Pain and Damage
`Routes of Drug Injection
`Cutaneous/Subcutaneous Injections
`Intramuscular Injections
`22
`Intra-arterial Injections
`24
`Intravenous Injections
`26
`Conclusions and Perspectives
`Acknowledgements
`References
`
`18
`
`3.
`
`Mechanisms of Muscle Damage with
`Injectable Products
`Anne McArdle and Malcolm J. Jackson
`
`Abstract
`Introduction
`Mechanisms of Muscle Damage
`Elevation of Intracellular Calcium Concentration
`60
`Increased Free Radical Production
`Loss of Energy Homeostasis
`61
`Methods of Assessing Drug-Induced Skeletal
`Muscle Damage
`Microscopic Analysis of Skeletal Muscle
`63
`Muscle Function Studies
`64
`Leakage of Intramuscular Proteins
`Microdialysis Studies of Individual Muscles
`65
`Cellular Stress Response
`Techniques to Assess the Mechanisms of Muscle Damage
`Models of Muscle Damage
`66
`Techniques to Show Changes in Muscle Calcium Content
`Markers of Increased Free Radical Activity
`67
`Methods of Measuring Cellular Energy Levels 67
`Conclusions
`Acknowledgments
`References
`
`62
`
`64
`
`58
`
`66
`
`15
`
`15
`16
`18
`
`49
`50
`50
`
`57
`
`57
`57
`58
`
`62
`
`66
`
`67
`67
`68
`
`Page 4 of 33
`
`

`

`Contents
`
`v
`
`B: METHODS TO ASSESS PAIN, IRRITATION, AND
`MUSCLE DAMAGE FOLLOWING INJECTIONS
`
`4.
`
`In Vitro Methods for Evaluating
`Intravascular Hemolysis
`Joseph F. Krzyzaniak and Samuel H. Yalkowsky
`
`Significance
`In Vitro Methods for Evaluating Hemolysis
`Static Methods
`81
`Dynamic Methods
`82
`Comparison of In Vitro and In Vivo Hemolysis Data
`Summary of In Vitro Methods
`References
`
`5.
`
`Lesion and Edema Models
`Steven C. Sutton
`Edema and Inflammation
`Lesion Models
`Rabbit
`92
`Mice
`96
`Rat
`96
`Biochemical Models
`Serum Glutamic-Oxaloacetic Transaminase
`N-Acetyl-13-Glucosaminidase
`97
`Myeloperoxidase
`97
`Creatine Kinase
`98
`Edema Models
`105
`Inducing Edema
`Exudative Models of Inflammation
`Vascular Permeability Models
`105
`Footpad Edema Models
`106
`Correlation of Models
`Rabbit Lesion Versus Rabbit Hemorrhage Score Model
`Rabbit Lesion Versus Rabbit CK Model
`108
`Rabbit Lesion Versus Rat Footpad Edema Model
`Rabbit Lesion Versus Rat CK Model
`109
`Rat and Human
`110
`
`97
`
`105
`
`77
`
`78
`79
`
`85
`86
`87
`
`91
`
`91
`92
`
`97
`
`105
`
`107
`
`107
`
`109
`
`Page 5 of 33
`
`

`

`vi
`
`Injectable Drug Development
`
`111
`
`Models for Extended-Release Formulations
`Predicting Muscle Damage from
`Extended-Release Formulations
`Future Directions
`112
`Muscle Damage and CK
`Gamma Scintigraphy
`112
`Electron Parametric Resonance and
`Nuclear Resonance Imaging
`112
`Effect of Edema and Lesion on Bioavailability
`Formulation
`113
`Conclusions
`References
`
`113
`
`6.
`
`Rat Paw-Lick Model
`Pramod K. Gupta
`
`Methodology
`Correlation Between Rat Paw-Lick and Other
`Pain/Irritation Models
`Application of Rat Paw-Lick Model to Screening
`Cosolvent-Based Formulations
`Limitations of the Rat Paw-Lick Model
`Concluding Remarks
`References
`
`7.
`
`Radiopharmaceuticals for the Noninvasive
`Evaluation of Inflammation Following
`Intramuscular Injections
`Agatha Feltus, Michael Jay, and Robert M. Beihn
`
`Gamma Scintigraphy
`Gamma Cameras
`Detectors
`133
`Collimators
`135
`Electronics and Output
`Computers
`137
`Tomographic Imaging
`Quality Control
`139
`Radionuclides and Radiation
`Scintigraphic Detection of Inflammation ·
`
`136
`
`139
`
`110
`
`112
`
`114
`115
`
`119
`
`120
`
`120
`
`123
`126
`128
`128
`
`131
`
`132
`132
`
`140
`141
`
`Page 6 of 33
`
`

`

`Contents
`
`vii
`
`141
`Gallium-67
`143
`Radiolabeled Leukocytes
`Radiolabeled Antibodies
`145
`Other Radiopharmaceuticals
`Summary
`References
`
`147
`
`8.
`
`A Primer on In Vitro and In Vivo Cytosolic
`Enzyme Release Methods
`Gayle A Brazeau
`
`160
`
`164
`
`Rationale for Utilizing Release of Cytosolic Components
`as a Marker of Tissue Damage
`Experimental Models
`Isolated Rodent Skeletal Muscle Model
`General Experimental Overview
`159
`Isolation, Extraction, and Viability of Isolated Muscles
`Muscle Exposure to the Test Formulation
`162
`Incubation Media
`164
`Cytosolic Enzymes Utilized in Isolated Muscle Studies
`Controls and Data Analysis
`164
`Muscle Cell Culture Methods to Evaluate Muscle Injury
`General Considerations
`165
`General Considerations in the Optimization of Experimental
`Cell Culture Systems
`166
`Selected Cell Lines in Screening for Drug-Induced Toxicity
`In Vivo Enzymatic Release Methods
`General Considerations
`169
`Animal Models
`170
`Quantification of Tissue Damage
`Conclusions
`Acknowledgments
`References
`
`171
`
`9.
`
`Histological and Morphological Methods
`Bruce M. Carlson and Robert Palmer
`
`Basic Principles Underlying Morphological Analysis
`Techniques of Morphological Analysis
`
`148
`149
`
`155
`
`157
`159
`159
`
`165
`
`168
`
`169
`
`172
`173
`173
`
`177
`
`179
`180
`
`Page 7 of 33
`
`

`

`viii
`
`Injectable Drug Development
`
`180
`
`Electron Microscopic Methods
`Histological Methods
`183
`Histochemical Methods
`185
`187
`Immunocytochemical Methods
`Neuromuscular Staining Methods
`189
`Summary of Strengths and Limitations of
`Morphological Techniques in Assessing
`Muscle Damage After Injections
`References
`
`10. Conscious Rat Model to Assess Pain
`Upon Intravenous Injection
`John M. Marcek
`Experimental Procedures
`Experiment 1
`196
`Experiment 2
`197
`Experiment 3
`197
`Experiment 4
`197
`Experiment 5
`197
`Experiment 6
`197
`Experiment 7
`198
`Statistical Analyses
`Results
`Discussion
`Applications
`Summary and Conclusions
`Acknowledgments
`References
`
`198
`
`C: APPROACHES IN THE DEVELOPMENT OF
`LESS-PAINFUL AND LESS-IRRITATING INJECTABLES
`
`11. Cosolvent Use in Injectable Formulations
`Susan L. Way and Gayle Brazeau
`
`Commonly Used Solvents
`Polyethylene Glycols
`219
`
`Propylene Glycol
`Ethanol
`225
`
`223
`
`190
`191
`
`193
`
`195
`
`198
`204
`209
`210
`211
`211
`
`215
`
`218
`
`Page 8 of 33
`
`

`

`Contents
`
`ix
`
`· 226
`Glycerin
`Cremophors
`227
`Benzyl Alcohol
`228
`Amide Solvents
`230
`Dimethylsulfoxide
`232
`Hemolytic Potential of Solvents/Cosolvents
`In Vitro/In Vivo Hemolysis Comparisons
`237
`Muscle Damage
`Cosolvent-Related Pain on Injection
`Cosolvents Known to Cause Pain
`245
`Methods to Minimize Pain
`247
`Conclusions
`References
`
`12. Prodrugs
`
`Laszlo Prokai and Katalin Prokai-Tatrai
`
`Design of Prodrugs
`Specific Examples of Prodrugs Developed to Improve
`Water Solubility of Injectables
`Anticancer Agents
`273
`Central Nervous System Agents
`Other Drugs
`288
`Conclusions
`References
`
`283
`
`13. Complexation-Use of Cyclodextrins to
`Improve Pharmaceutical Properties of
`Intramuscular Formulations
`Marcus E. Brewster and Thorsteinn Loftsson
`Cyclodextrins
`Preparation of Cyclodextrin Complexes
`Characterization of Cyclodextrin Complexes
`Use of Cyclodextrins in IM Formulations
`Methodologies
`319
`IM Toxicity of Cyclodextrins and Their Derivatives
`Use ofCyclodextrins to Replace Toxic Excipients
`in IM Formulations
`323
`Use of Cyclodextrins to Reduce Intrinsic
`Drug-Related Toxicity
`326
`
`320
`
`233
`
`242
`245
`
`250
`251
`
`267
`
`267
`
`273
`
`295
`297
`
`307
`
`308
`312
`313
`319
`
`Page 9 of 33
`
`

`

`x
`
`Injectable Drug Development
`
`Conclusions and Future Directions
`Acknowledgments
`References
`
`14. Liposomal Formulations to Reduce
`Irritation of Intramuscularly and
`Subcutaneously Administered Drugs
`Farida Kadir, Christien Oussoren, and Daan I. A Crommelin
`Liposomes: A Short Introduction
`Liposomes as Intramuscular and Subcutaneous
`Drug Delivery Systems
`Studies on Reduction of Local Irritation
`Studies on the Protective Effect After
`Intramuscular Administration
`342
`Studies on the Protective Effect After Intradermal and
`Subcutaneous Administration
`345
`Discussion
`Conclusions
`References
`
`15. Biodegradable Microparticles for the
`Development of Less-Painful and
`Less-Irritating Parenterals
`Elias Fattal, Fabiana Quaglia, Pramod Gupta, and Gayle Brazeau
`
`Rationale for Using Microparticles in the Development
`of Less-Painful and Less-Irritating Parenterals
`Poly(Lactide-co-Glycolide) Microparticles as Delivery
`Systems in the Development of Less-Painful and
`Less-Irritating Parenterals
`Polymer Selection
`357
`Microencapsulation Technique
`Drug Release
`366
`Sterilization
`368
`Residual Solvents
`368
`Stability of the Encapsulated Drug and
`Microparticle Products
`369
`Protection Against Myotoxicity by Intramuscularly/
`Subcutaneously Administered Microparticles
`
`360
`
`329
`330
`330
`
`337
`
`338
`
`340
`341
`
`349
`350
`351
`
`355
`
`356
`
`357
`
`370
`
`Page 10 of 33
`
`

`

`Contents
`
`xi
`
`Conclusions
`References
`
`16. Emulsions
`Pramod K. Gupta and John B. Cannon
`
`Rationale for Using Emulsions for Reducing Pain and
`Irritation upon Injection
`Potential Mechanisms of Pain on Injection
`Case Studies
`Propofol (Diprivan®)
`Diazepam
`384
`Etomidate
`388
`Pregnanolone (Eltanolone®)
`
`382
`
`388
`
`389
`
`Methohexital and Thiopental
`Amphotericin B
`390
`Clarithromycin
`391
`Challenges in the Use of Emulsions as Pharmaceutical
`Dosage Forms
`Physical Stability
`Efficacy
`393
`Dose Volume
`Other Issues
`Conclusions
`References
`
`393
`
`394
`394
`
`D: FUTURE PERSPECTIVES IN THE DEVELOPMENT OF
`LESS-PAINFUL AND LESS-IRRITATING INJECTABLES
`
`17. Formulation and Administration Techniques
`to Minimize Injection Pain and Tissue
`Damage Associated with Parenteral Products
`Larry A Gatlin and Carol A Gatlin
`
`Formulation Development
`?reformulation
`402
`Formulation
`404
`Focus on Osmolality, Cosolvents, Oils, and pH
`pH
`415
`
`410
`
`371
`372
`
`379
`
`380
`381
`382
`
`393
`
`395
`395
`
`401
`
`402
`
`Page 11 of 33
`
`

`

`xii
`
`Injectable Drug Development
`
`Post-Formulation Procedures
`pH, Additives, and Solvents
`416
`Devices and Physical Manipulations
`References
`
`417
`
`Index
`
`416
`
`420
`
`423
`
`Page 12 of 33
`
`

`

`17
`
`Formulation and
`Administration Techniques
`to Minimize Injection Pain
`and Tissue Damage
`Associated with Parenteral
`Products
`
`Larry A. Gatlin
`Biogen, Inc.
`Cambridge, Massachusetts
`
`Carol A. Brister Gatlin
`Genzyme
`Cambridge, Massachusetts
`
`Parenteral products significantly contribute to global health by providing
`effective and immediate therapy through direct delivery of therapeutic
`compounds to the patient. However, as with most routes of delivery, par(cid:173)
`enteral drug administration has both real and perceived disadvantages.
`The two potential disadvantages that are typically associated with par(cid:173)
`enteral therapy are tissue damage and injection pain. Whether this pain is
`real or imagined makes little difference to the patient, and there exists a
`significant literature that both highlights the pain caused by injectable
`drug products and offers methods to reduce these effects.
`The first section of this chapter provides a strategy that can be used
`to develop a parenteral product. Emphasis is placed on the two formula(cid:173)
`tion parameters, . pH and tonicity, that are usually associated with tissue
`damage and injection pain. It is through the adjustment of these parame(cid:173)
`ters that the product formulator can minimize adverse effects. The second
`section of this chapter describes administration techniques used by
`
`401
`
`Page 13 of 33
`
`

`

`402
`
`Injectable Drug Development
`
`healthcare professionals to reduce tissue damage or pain caused by com(cid:173)
`mercial parenteral products. By recognizing the potential risks these al(cid:173)
`terations may confer to commercial formulations (such as decreased
`product stability or modified efficacy), the formulator will be better pre(cid:173)
`pared to support the "real-world" use of the product.
`
`FORMULATION DEVELOPMENT
`
`The development strategy for parenteral products is similar for all prod(cid:173)
`ucts. The challenge is in the details of solving the physical/chemical diffi(cid:173)
`culties encountered with a specific molecule within the timeline allowed
`for development. This section provides a parenteral product development
`outline with an emphasis on two formulation parameters, pH and tonicity,
`which may be modified to minimize tissue damage and pain caused by a
`parenteral product.
`The activities necessary to develop a parenteral product can be placed
`into the following three broad areas: preformulation, formulation, and
`scale-up. While there are alternative development perspectives, all devel(cid:173)
`opment ultimately needs to accomplish the same activities. Preformulation
`includes the characterization of the bulk drug plus initial screening for ex(cid:173)
`cipient compatibility with the drug. Formulation activities include the iden(cid:173)
`tification and selection of a suitable vehicle (aqueous, nonaqueous, or
`cosolvent system), necessary excipients with appropriate concentrations
`(buffers, antioxidants, antimicrobials, chelating agents, and tonicity con(cid:173)
`tributors), and the container/closure system. Scale-up activities aid in mov(cid:173)
`ing the product to a manufacturing site (although not discussed here,
`references are available to provide guidance).
`
`Preformulation
`
`Preformulation studies provide fundamental data and the experience nec(cid:173)
`essary to develop formulations for a specific compound. Activities are
`initiated and experiments performed for the purpose of characterizing
`specific and pharmaceutically significant physicochemical properties of
`the drug substance. These properties include interactions of the drug with
`excipients, solvents, packaging materials, and, specifically relating to the
`subject of this book, biological systems. These investigations also evaluate
`the drug under standard stress conditions of temperature, light, humidity,
`and oxygen. Many of these factors should be considered critically prior to
`animal testing, since these data will influence activities such as samples
`prepared for toxicology and animal testing, solubilization techniques, and
`design of subsequent studies.
`
`Page 14 of 33
`
`

`

`Formulation and Administration Techniques
`
`403
`
`Areas of specific interest during preformulation are provided in out(cid:173)
`line form below, along with an outline of additional characterization infor(cid:173)
`mation needed to formulate a protein drug substance. Since analytical
`methods are usually developed concurrently with the preformulation data
`and then refined during formulation activities, the team must effectively
`communicate and collaborate to ensure appropriate assays are used to ob(cid:173)
`tain data having sufficient accuracy and precision.
`
`Preformulation Physicochemical Properties
`
`1. Molecular weight
`
`2. Color
`
`3. Odor
`
`4.
`
`5.
`
`Particle size, shape, and crystallinity
`
`Thermal characteristics
`
`5.1. Melting profile
`
`5.2. Thermal profile
`
`6. Hygroscopicity
`
`7. Absorbance spectra
`
`8.
`
`Solubility
`
`8.1. Selected solvents (water, ethanol, propylene glycol, poly(cid:173)
`ethylene glycol 400, plus others as necessary)
`
`8.2. pH profile
`
`8.3. Temperature effects
`
`8.4. Partition coefficient
`
`9.
`
`Stability
`
`9.1. Selected solvents
`
`9.2. pH profile
`
`10.
`
`Ionization constant (pK or pi)
`
`11. Optical activity
`
`Page 15 of 33
`
`

`

`404
`
`Injectable Drug Development
`
`Additional Characterization for Protein Drugs
`
`1.
`
`Physical stability
`
`1.1. Aggregation
`
`2.
`
`Solubility
`
`3. Chemical stability
`
`3.1. Beta-elimination
`
`3.2. Deamidation
`
`3.3.
`
`Isomerization/cyclization
`
`3.4. Oxidation
`
`3.5. Thiol disulfide exchange
`
`4. Analytical methods
`
`4.1. Fluorescence spectroscopy
`
`4.2. Electrophoresis
`
`4.3. Calorimetry
`
`4.4. Size exclusion chromatography
`
`4.5. Reverse phase high performance liquid chromatography
`(HPLC)
`
`4.6. Circular dichroism
`
`4.7. Mass spectrometry
`
`4.8. Light scattering
`
`Formulation
`
`Formulation activities include the identification and selection of a suitable
`vehicle (aqueous, nonaqueous, or cosolvent system), necessary excipients·
`with appropriate concentrations (buffers, antioxidants, antimicrobials,
`chelating agents, and tonicity contributors), and the container/closure sys(cid:173)
`tem. The formulator is interested in the same list of activities given for pre(cid:173)
`formulation; however, the activities are focused on specific excipients and
`characterization of the formulation. The principles of formulating a par(cid:173)
`enteral product have been outlined by several authors, although most do
`not specifically include the evaluation of tissue damage or pain caused by
`injection of the final product. This is likely due to the assumption that
`
`Page 16 of 33
`
`

`

`Formulation and Administration Techniques
`
`405
`
`deviation of pH or tonicity from physiological conditions causes these ef(cid:173)
`fects. It is, however, important to consider that a product may cause tissue
`damage with little associated pain, pain with little tissue damage, or both
`pain and tissue damage. Therefore, the models utilized to assess either the
`pain or tissue damage associated with a product need to be selected care(cid:173)
`fully. Several complementary methods may be needed, and these models
`are provided throughout this book.
`Significant formulation activities begin with initial preformulation
`data and knowledge of the specific route of administration. These data
`provide the formulator with the requirements and limitations for the final
`formulation. Due to the location of human pain receptors, formulation ap(cid:173)
`proaches to reduce pain are more critical for subcutaneous (SC) and intra(cid:173)
`dermal injections and less critical for intramuscular (IM) and intravenous
`(IV) administration.
`Injection volume is one of the most important considerations in the
`formulation development of a commercial product. This volume is selected
`based on the proposed injection route. Since veins have a relatively large
`volume and blood flow rate, a product administered by the IV route can
`have a volume greater than 10 mL; as the volume increases, the delivery
`rate may need to be controlled. This is in contrast to IM injections, which
`are normally limited to 3 mL, SC injections to 1 mL, and intradermal injec(cid:173)
`tions to 0.2 mL. Recommended maximum injection volumes are author de(cid:173)
`pendent but not radically different.
`Thus, the factors that need to be considered in evaluating the hemol(cid:173)
`ysis caused by a product include both the quantity and proportions of the
`substances and how rapidly the blood dilutes the product. The data in
`Table 17.1 provide some perspective on the vascular system's capability of
`diluting an injected IV product, in terms of both volume and rate. The
`choice of solvent is dependent both on the route of administration, which
`
`Table 17 .1. Physical Characteristics of the Arteriovenous System
`Volume (cm3)
`Anatomical Section
`Velocity (em/sec)
`
`Aorta
`
`Arteries
`
`Arterioles
`
`Capillaries
`
`Venules
`
`Veins
`
`Vena cava
`
`100
`
`325
`
`50
`
`250
`
`300
`
`2,200
`
`300
`
`40
`
`40-100
`
`10-0.1
`
`0.1
`
`0.3
`
`0.3-5
`
`5-30
`
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`Injectable Drug Development
`
`as noted above imparts volume limitations, and on drug solubility in the se(cid:173)
`lected solvent. IV injections are typically restricted to dilute aqueous solu(cid:173)
`tions to ensure compatibility with the blood; however, IM or SC injections
`allow for oily solutions, cosolvent systems, suspensions, or emulsions.
`Pain, soreness, and inflammation of tissues are frequently observed in the
`administration of parenteral suspensions, particularly with products hav(cid:173)
`ing a high solid content.
`A third important consideration in the development of a parenteral
`product is compatibility of the formulation with the tissue. An isotonic so(cid:173)
`lution is less irritating, causes less toxicity and pain, and minimizes hemol(cid:173)
`ysis. An isotonic product, however, is not always the goal since for SC or
`IM injections a hypertonic solution may facilitate drug absorption. Having
`an isotonic product is, however, very important for intraspinal injections,
`where the fluid circulation is slow and abrupt changes in osmotic pressure
`can contribute to unwanted and potentially severe side effects.
`The choice of acceptable excipients in parenteral product develop(cid:173)
`ment remains limited compared to other dosage forms, due to concerns of
`injection safety and feasibility of sterilization. In order to avoid uncertainty
`and reduce development time, most formulators select excipients success(cid:173)
`fully used in marketed products. A short list of commonly used additives,
`their functions, and typical concentrations is given in Tables 17.2 and 17.3.
`As the number of biotechnology products increases, excipients such as hu(cid:173)
`man serum albumin (HSA), amino acids, and sucrose are finding increas(cid:173)
`ing utility. In Europe, the use of animal-derived excipients such as HSA and
`some polysorbate surfactants has become problematic due to the increas(cid:173)
`ing concern with bovine spongiform encephalitis (BSE). This concern is
`expanding to the rest of the world and has impact on the selection of
`excipients.
`An excipient selected for a parenteral product may serve one or more
`purposes. For example, benzyl alcohol is primarily a preservative; how(cid:173)
`ever, it has a transient local anesthetic property. Dual roles may help in the
`goal to minimize both the number of product ingredients and their quan(cid:173)
`tity. The justification for each selection will become a part of the formula(cid:173)
`tion development report.
`
`Antimicrobials
`
`Preservatives are always included in a product when multiple doses will be
`drawn from a single vial unless the drug itself is bacteriostatic. The addi(cid:173)
`tion of an antimicrobial is not a substitute for good manufacturing prac(cid:173)
`tices; however, many times they are added to single-use containers. They
`are specifically excluded from large-volume products intended for
`infusion. In some cases, as with benzyl alcohol, the excipient may have
`multiple functions. Therefore, the decision whether or not to include a
`preservative in a single-use product may be product specific. The rationale
`
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`407
`
`Table 17.2. Additives Commonly Used in Parenteral Products
`
`Substance
`
`Concentration (percent)
`
`Antimicrobial
`
`Benzalkonium chloride
`
`Benzethonium chloride
`
`Benzyl alcohol
`
`Chlorobutanol
`
`Chlorocresol
`
`Metacresol
`
`Phenol
`
`Methyl p-hydroxybenzoate
`
`Propyl p-hydroxybenzoate
`
`Butyl p-hydroxybenzoate
`
`Antioxidants
`
`Acetone sodium bisulfite
`
`Ascorbic acid
`
`Ascorbic acid esters
`
`Butylhydroxyanisole (BHA)
`
`Butylhydroxytoluene (BHn
`
`Cysteine
`
`Monothioglycerol
`
`Sodium bisulfite
`
`Sodium metabisulfite
`
`Tocopherols
`
`Glutathione
`
`Surfactants
`
`0.01
`
`0.01
`
`1-2
`
`0.25-0.5
`
`0.1-0.3
`
`0.1-0.3
`
`0.5
`
`0.18
`
`0.02
`
`0.015
`
`0.2
`
`0.1
`
`0.015
`
`0.02
`
`0.02
`
`0.5
`
`0.5
`
`0.15
`
`0.2
`
`0.5
`
`0.1
`
`Polyoxethylene sorbitan monooleate
`
`Sorbitan monooleate
`
`0.1-0.5
`
`0.05-0.5
`
`for any preservative addition should be a part of the product development
`report.
`Common antimicrobial agents are given in Table 17.2. These agents
`are grouped into five chemical classes: quaternary ammonium com(cid:173)
`pounds, alcohols,-esters, mercurials, and acids. The alcohols and esters are
`commonly used in parenteral products. The quaternary compounds, which
`are commonly used in ophthalmic products, are not compatible with neg(cid:173)
`atively charged ions or molecules.
`
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`
`Table 17.3. Common Buffers Used in Parenteral Formulations
`Usual Buffering Range
`
`Buffer
`
`PKa
`
`Acetic acid
`
`Citric acid
`
`Glutamic acid
`
`Phosphoric acid
`
`Benzoic acid
`
`Lactic acid
`
`Ascorbic acid
`
`Tartaric acid
`
`Succinic acid
`
`Adipic acid
`
`Glycine
`
`Malic acid
`
`Triethanolamine
`
`Diethanolamine
`
`Tromethamine
`
`4.8
`
`3.14, 4.8, 5.2
`
`2.2, 4.3, 9.7
`
`2.1, 7.2, 12.7
`
`4.2
`
`3.1
`
`4.2, 11.6
`
`3.0, 4.3
`
`4.2, 5.6
`
`4.4, 5.28
`
`2.34, 9.6
`
`3.4, 5.1
`
`8.0
`
`9.0
`
`8.1
`
`3.5-5.7
`
`2.1-6.2
`
`8.2-10.2
`
`2-3.1, 6.2-8.2
`
`3.2-5.2
`
`2.1-4.1
`
`3.2-5.2
`
`2.0-5.3
`
`3.2-6.6
`
`3.4-6.3
`
`1.5-3.5, 8.8-10.8
`
`2.4-6.1
`
`7-9
`
`8.0-10.0
`
`7.1-9.1
`
`The literature reports interactions of the parabens with surfactants
`and formation of molecular complexes with gelatin, methylcellulose,
`polyvinyl pyrrolidone, and polyethylene glycol. These interactions may de(cid:173)
`crease preservative efficacy. Some antimicrobial compounds, such as ben(cid:173)
`zyl alcohol, may be adsorbed by the container closure. Thus, microbial
`preservation must be demonstrated for the final formulated product.
`
`Buffers
`
`The buffer system establishes and maintains the product pH. A specific
`buffer system is selected such that the pKa of the system is within one pH
`unit ofthe pH desired for the product. A list of common buffers is provided
`in Table 17.3. The selection of the product pH is based on the stability of the
`active drug. When alternative buffers are available, a comparison of their
`respective effects on stability will usually aid in the final choice. The acetate
`buffer system is not a good choice for a lyophilized product due to the
`volatility of acetic acid. Loss of acetic acid results in a pH shift when the
`product is reconstituted. The pH of solutions containing a phosphate
`buffer system have been shown to shift during cooling due to precipitation
`of sodium phosphate species. These pH shifts during freezing may cause
`
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`Formulation and Administration Techniques
`
`409
`
`damage to a protein. Since the specific buffer and the buffer capacity can
`contribute to injection pain, these effects should be evaluated in the selec(cid:173)
`tion of the buffer. Each species of the buffer system affects the tonicity of
`the final product; this influence must be considered during product devel(cid:173)
`opment. For example, as the pH of a formulation containing monosodium
`phosphate is adjusted, the disodium salt is formed and contributes to prod(cid:173)
`uct tonicity.
`
`Antioxidants
`
`Preformulation data will identify compounds sensitive to oxidation. Free
`radicals or molecular oxygen mediates oxidation, and several alternative
`stabilization approaches are available. In many cases, several approaches
`are utilized concurrently. One approach is lowering the product pH, which,
`according to the Nernst equation, increases the oxidation potential of the
`drug and thus increases stability. When oxygen contributes to degrada(cid:173)
`tion, it can be displaced during the filling operation by "bubbling" an inert
`gas such a nitrogen or argon gas through the solution prior to filling the
`vials. Additionally, the container headspace can be overlaid with the inert
`gas. An antioxidant may be useful if further protection is necessary. The
`specific antioxidant selected should have a lower oxidation potential than
`the drug. Several antioxidants and concentrations should be evaluated be(cid:173)
`cause, in many cases, a single agent is not sufficient. Sulfites are associated
`with allergic reactions in some patients. This reaction has a rapid onset and
`is not always confirmed by an oral challenge. Despite this reaction poten(cid:173)
`tial, sulfites may be used in a formulation if necessary to stabilize a life(cid:173)
`saving product.
`Examples of antioxidants include sodium bisulfite, ascorbic acid, glu(cid:173)
`tathione, and propyl gallate. Sodium bisulfite tends to react irreversibly
`with the double bonds found in aldehydes and some ketones, and fre(cid:173)
`quently results in a significant loss of biological activity. Epinephrine forms
`a bisulfite addition product, as do other sympathomimetic drugs having
`ortho- or para-hydroxybenzyl alcohol derivatives. The meta-hydroxy alco(cid:173)
`hol does not react with sodium bisulfite. Sulfites are converted to sulfates
`in' the oxidation reaction, and if small amounts of barium are present, a
`precipitate will form.
`
`Chelating Agents
`
`Chelating agents are used to increase the solubility of a drug or to impart
`some product stability. Compounds such as ascorbic acid, citric acid, and
`ethylenendiaminetetraacetic acid chelate metals, which would otherwise
`catalyze oxidation reactions, and provide measurable benefits for some
`products.
`
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`Injectable Drug Development
`
`Surfactants
`
`Surfactants are used to solubilize a drug and, for protein products, to min(cid:173)
`imize adsorption of the protein on surfaces. Most polysorbates are derived
`from animal sources, and their use in Europe is becoming problematic due
`to the increasing concerns with BSE. This concern is expanding to the rest
`of the world and will impact in the selection of excipients. Several suppli(cid:173)
`ers are beginning to offer polysorbates from vegetable sources. Polysor(cid:173)
`bates can contain peroxides that may adversely affect product stability
`and, as for all excipients, specifications will need to be established.
`
`Tonicity Agents
`
`The active drug and each excipient contribute to the tonicity of the formu(cid:173)
`lation. When the tonic contribution of these combined ingredients is not
`sufficient to provide an isotonic solution, then tonicity agents, such as dex(cid:173)
`trose, sodium chloride (NaCl), sodium sulfate, or mannitol can be added.
`Additional details are provided in the osmolality section below.
`In summary, formulation activities focus on the selection of the
`solvent, the necessary excipients (buffers, antimicrobials, antioxidants,
`chelating agents, surfactants, and tonicity agents) with corresponding con(cid:173)
`centrations, the container/closure system, and on demonstrating adequate
`stability.
`
`Focus on Osmolality, Cosolvents, Oils, and pH
`
`The contribution of isotonicity in reducing injection pain is not always
`clear but, at a minimum,