INJECTABLE DRUG
`
`DEVELOPMENT
`
`TECHNIQUES TO REDUCE
`PAIN AND IRRITATION
`
`Edited by
`
`Pramod K. Gupta
`
`and
`
`Gayle A. Brazeau
`
`Interpharm Press
`Denver, Colorado
`
`
`
`INTERPHARM"
`P R E S S
`
`AstraZeneca Exhibit 2079 p. 1
`InnoPharma Licensing LLC v. AstraZeneca AB IPR2017-00905
`
`

`

`Invitation to Authors
`
`dustries, please contact our director of publications.
`
`____._, Interpharm Press publishes books focused upon applied tech—
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`:'- nology and regulatory affairs impacting healthcare manufactur-
`...——-=== ers worldwide. It‘ you are considering writing or contributing to
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`_
`
`Library of Congress Catalogingain-Puhlication Data
`
`lnjectable drug development : techniques to reduce pain and irritation !
`edited by Framed K.- Gupta and Gayle A. Brazeau.
`p.
`cm.
`
`Includes bibliographical references and index.
`ISBN 1-57491i095-7
`
`1. Injections. 2. lniections—Complications. 3. Drug development.
`I. Gupta, Pramod FL. 1959—
`. Ii. Brazeau. Gayle A.
`lDNLM: 1. Injections—adverse effects. 2. Pain—chemically induced.
`3. Pain—prevention 8: control. 4. Pharmaceutical Preparations—
`administration 8: dosage. WB 354 156 1999]
`RM159J49
`1999
`B‘lS'.6—-—dc21
`DNLMJDLC
`
`for Library of Congress
`
`99-25911
`CIP
`
`10987654321
`
`ISBN: 1-57491-095-7
`
`Copyright © 1999 by Interpharm Press- All rights reserved.
`
`All rights reserved. This book is protected by copyright. No part of it maybe re-
`producad, stored in a retrieval system, or transmitted in any form or by any
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`written permission from the publisher. Printed in the United States of America.
`Where a product trademark, registration mark, or other protected mark is
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`mark. No claim. intentional or otherwise. is made by reference to any such marks
`in this book.
`
`While every effort has been made by Interphartn Press to ensure the accuracy
`of the information contained in this book. this organization accepts no responsi-
`bility for errors or omissions.
`
`Interpharm Press
`’15 lnverness Way E.
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`
`AstraZeneca Exhibit 2079 p. 2
`
`

`

`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
`
`3
`
`10
`
`11
`
`11
`
`‘13
`
`‘14
`
`iii
`
`AstraZeneca Exhibit 2079 p. 3
`
`

`

`iv
`
`2.
`
`lnjectable 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
`
`1'8
`
`Intramuscular Injections
`
`22
`
`[mm-arterial Injections
`
`24
`
`Intravenous Injections
`
`26
`
`Conclusions and PerSpectives
`
`Acknowledgements
`
`References
`
`Mechanisms of Muscle Damage with
`Injectable Products
`
`Anne McArdle and Malcolm J. Jackson
`
`Abstract
`
`Introduction
`
`Mechanisms of Muscle Damage
`
`Elevation oflntracellular Calcium Concentration
`
`58
`
`Increased Free Radical Production
`
`60
`
`Loss of Energy Homeostasis
`
`51
`
`Methods of Assessing Drug—Induced Skeletal
`Muscle Damage
`
`Microscopic Analysis of Skeletal Muscle
`
`62
`
`Muscle Function Studies
`
`63
`
`Leakage of Intramuscular Proteins
`
`64
`
`Mitrodialysis Studies ofIndividual Muscles
`
`64
`
`Cellular Stress Response
`
`65
`
`15
`
`‘15
`
`16
`
`‘18
`
`49.
`
`50
`
`50
`
`57
`
`57
`
`57
`
`58
`
`6.2
`
`Techniques to Assess the Mechanisms of Muscle Damage
`
`66
`
`Models of Muscle Damage
`
`66
`
`Techniques to Show Changes in Muscle Calcium Cement
`
`66
`
`Markers oflncreased Free Radical Activity
`
`67
`
`Methods ofMeasuring Cellular Energy Levels
`
`6?
`
`Conclusions
`
`Acknowledgments
`
`References
`
`6?
`
`67
`
`68
`
`AstraZeneoa Exhibit 2079 p. 4
`
`

`

`Contents
`
`v
`
`B: METHODS T0 ASSESS PAIN,- IRRITATION, AND
`MUSCLE DAMAGE FOLLOWING INJECTIONS
`
`In. Vitro Methods for Evaluating
`Intravascular Hemolysis
`
`Joseph E 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
`
`Lesion and Edema Models
`
`Steven C Sutton
`
`Edema and Inflammation
`
`Lesion Models
`
`Rabbit
`
`92
`
`Mice
`
`96
`
`Her
`
`96
`
`Biochemical'Models
`
`Serum Giutamic—Oxaloacetic Transaminase
`
`97
`
`N-Acetyi-B-Glucosaminidase
`
`.97
`
`MyeiOperoxidase
`
`9?
`
`Creatine Kinase
`
`98
`
`Edema Models
`
`inducing Edema
`
`105
`
`Exudative Models oflnflammation
`
`105
`
`Vascular Permeability Models
`
`105
`
`Footpad Edema Models
`
`106
`
`Cert-elation of Models
`
`Rabbit Lesion Versus Rabbit Hemorrhage Score Model
`
`10?
`
`Rabbit Lesion Versus Rabbit CK Model
`
`1'08
`
`Rabbit Lesion Versus Rat Footpad Edema Modei
`
`109
`
`Rabbit Lesion Versus Rat CK Model
`
`109
`
`Rat and Human
`
`110
`
`77
`
`is
`
`79
`
`85
`
`.86
`
`87'
`
`91
`
`91
`
`92-
`
`97'
`
`‘105
`
`107
`
`AstraZeneca Exhibit 2079 p. 5
`
`

`

`vi
`
`Injeclable Drug Development
`
`Models for Extended-Release Formulations
`
`Predicting Muscle Damage fmm
`Extended-Release Formulations
`
`111
`
`Future Directions
`
`Muscle Damage and CK 112
`
`Gamma Scintigrapny
`
`112
`
`Electron Parametric Resonance and
`
`Nuclear Resonance Imaging
`
`1‘12
`
`Effect of Edema and Lesion on Bioavailabilily
`
`1'13
`
`Fonnulalion
`
`1 13
`
`Conclusions
`
`References
`
`Rat Paw-Lick Model
`
`Pramoo‘ 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
`
`Radiopharmaceuticals for the Noninvasive
`Evaluation of Inflammation Following
`Intramuscular Injections
`
`Agatha Feltus, Michael Jay, and Robert M. Beihn
`
`Gamma Scintigraphy
`
`Gamma Cameras
`
`Detectors
`
`I33
`
`Colllmalors
`
`135
`
`Electronics and Output
`
`136
`
`Computers
`
`137
`
`Tomographlc Imaging
`
`1139
`
`Quality Control
`
`139
`
`Radionuclides. and Radiation
`
`Scintigraphic Detection of Inflammation
`
`1‘10
`
`1'12
`
`1‘14
`
`‘115
`
`1‘19
`
`120
`
`120
`
`“123
`
`126
`
`128
`
`128
`
`131
`
`‘132
`
`132
`
`140
`
`141
`
`AstraZencca Exhibit 2079 p. 6
`
`

`

`Contents
`
`vii
`
`Gallium—67
`
`T41
`
`Radiolabeled Leukocytes
`
`Radiolabeled Antibodies
`
`143
`
`1-45
`
`Other Radiopharmaceuricals
`
`147
`
`Summary
`
`References
`
`A Primer on In Vitro and In Vivo Cytosolic
`Enzyme Release Methods
`
`Gayle A. Brazeau
`
`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 oflsolated Muscles
`
`160
`
`Muscle Exposure to the Test Formulation
`
`16.?
`
`Incubation Media
`
`164
`
`Cytoaolic Enzymes Utilized in Isolated Muscle Studies
`
`164
`
`Controls and Data Analysis
`
`164
`
`148
`
`149
`
`155
`
`15?
`
`159
`
`159
`
`Muscle Cell Culture Methods to Evaluate Muscle Injury
`
`155
`
`General Considerations
`
`165
`
`General Considerations in the Optimization of Experimental
`Cell Culture Systems
`166
`
`Selected Cell Lines in Screening for Drugblnduced Toxicity
`
`1'68
`
`In Vivo Enzymatic Release Methods
`
`General Considerations
`
`169
`
`Animal Models
`
`1 re
`
`Quantification of Tissue Damage
`
`1?!
`
`Conclusions
`
`Acknowledgments
`
`References
`
`Histological and Morphological Methods
`
`Bruce M. Carlson and Robert Palmer
`
`Basic Principles Underlying Morphological Analysis
`
`Techniques of Morphological Analysis
`
`169
`
`172
`
`173
`
`173
`
`177
`
`179
`
`“180
`
`AstraZeneca Exhibit 2079 p. 7
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`

`

`viii
`
`lnjectable Drug Development
`
`Electron Microscopic Methods
`
`180
`
`Histological Methods
`
`183
`
`Histochemical Methods
`
`185
`
`lmmunocytochemlcal Methods
`
`1-8?
`
`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'
`
`Emerlmente?
`
`ExperimentB
`
`Experiment4
`
`Experimentfi
`
`Experiment 6
`
`Experiment 7
`
`196
`
`197
`
`197
`
`19?
`
`19?
`
`1.9?
`
`198-
`
`Statlstlcal Analyses
`
`198
`
`Results
`
`Discussion
`
`Applications.
`
`Summary and Conclusions
`
`Acknowledgments
`
`References
`
`C: APPROACHES IN THE DEVELOPMENT OF
`
`LESS—PAINFUL AND LESS-IRRITATING INJECTABLES
`
`‘11.
`
`Cosol'vent Use in Injectable Formulations
`
`Susan L. Way and Gayle Brazeau
`
`Commonly Used Solvents
`
`Polyefliylene Glycols
`
`219
`
`Propylene Glycol
`
`223
`
`Ethanol
`
`225
`
`190
`
`191
`
`193
`
`‘195
`
`‘198
`
`204-
`
`209
`
`2‘10
`
`211
`
`2‘11
`
`215
`
`2‘18
`
`AstraZeneca Exhibit 2079 p. 8
`
`

`

`Contents
`
`ix
`
`Glycen'n
`
`226
`
`Cremophors
`
`22?
`
`Benzyl Alcohol
`Amide Solvents
`
`228
`23D
`
`Dimethylsultbxlde
`
`232
`
`Hemolytic Potential of SolventsICosolvents
`
`In Vitro/In Viva Hemolysis Comparisons
`
`237
`
`Muscle Damage
`
`Cosolvent—Related Pain on Injection
`
`Cosolvents Known to Cause Pain
`
`245
`
`Methods to Minimize Pain
`
`24?
`
`Conclusions
`
`References
`
`‘12.
`
`Prodrugs
`
`Laszlo- Prokai and Katalin Prokaf—Ta trai
`
`Design of Prodrugs
`
`Specific Examples of Prodrugs Developed to Improve
`Water Solubility of Injectables
`
`Anticancer Agents
`
`27’3
`
`Central Nervous System Agents
`
`283
`
`Other Drugs
`
`388
`
`Conclusions
`
`References
`
`‘13.
`
`Complexation—Use of Cyclodextrins to
`Improve Pharmaceutical Properties of
`Intramuscular Formulations
`
`Marcus E. Brewster and Thorstean Lofisson
`
`Cyclodextrins
`
`Preparation of Cyclodextr-in Complexes
`
`Characterization of Cyclodextrin Complexes
`
`Use of Cyclodextrins in IM Formulations
`
`Methodologies
`
`3.19
`
`[M Toxlclw'of Cyclodextn‘ns and Their Derivatives
`
`320
`
`Use of Cyclodextrins to Replace Toxic Excfpfen ts
`in HM Fonnulatlons
`323
`
`Use of Cydodex‘tn'ns to Reduce Intrinsic
`Drug-Related Toxicity
`326
`
`233
`
`242
`
`245
`
`250
`
`251
`
`267
`
`267
`
`273
`
`295
`
`297
`
`307
`
`308
`
`312
`
`313
`
`319
`
`AstraZeneca Exhibit 2079 p. 9
`
`

`

`x
`
`lnjectable Drug Development
`
`Conclusions and Future Directions
`
`Acknowledgments
`
`References
`
`‘14. Liposomal Formulations to Reduce
`Irritation of Intramuscularly and
`Subcutaneoust Administered Drugs
`
`Faricla Kao'll: Christien Oussoren, and" Dean J. A. Crommelin
`
`Liposomes: A Short Introduction
`
`Liposomes as Intramuscular and Subcutaneous
`Drug Deliveryr Systems
`
`Studies on Reduction of Local Irritation
`
`Studies on the Protective Efi'ect After
`Intramuscular Administration
`342
`
`Studies on the Protective Efiect Alter lntradermal and
`Subcutaneous Administration
`345
`
`Discussion
`
`Conclusions
`
`References
`
`15. Biodegradable Microparticles for the
`Development of Less-PainfiJ] 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
`
`PolytLactide-co-Glycolide] Micropa'rticles- as Delivery
`Systems in the Development of Less—Painful and
`Less—Irritating Pare'nte'rals
`
`329
`
`330
`
`330
`
`33?
`
`338
`
`340
`
`341
`
`3.49
`
`350
`
`351
`
`355
`
`35.6
`
`357'
`
`Polymer Selection
`
`357
`
`Mlcmencapsulatlon Technique
`
`360
`
`Drug Release
`
`366
`
`Sterilization
`
`368
`
`Residual Solvents
`
`368
`
`Stability of the Encapsulated Drug and
`Microparlicle Products
`369
`
`Protection Against Myotoxicity by Intramuscularly/
`Subcutane0usly‘ Administered Microparticles
`
`370
`
`Astra-Zeneca Exhibit 2079 p. 10
`
`

`

`Contents
`
`:0
`
`Conclusions.
`
`References
`
`‘16. Emulsions
`
`Framed 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
`
`Pmpofol (Diprivan®}
`
`382'
`
`Diazepam 384
`Etomidate
`388
`
`Pregnanolone (EltanoloneEJ
`
`388
`
`Methohexftal' and Thiopental
`
`389
`
`Amphotericin B
`
`390
`
`Clarithromycin
`
`3.91
`
`Challenges in the Use of Emulsions as Pharmaceutical
`Dosage For-ms
`
`Physical Stability
`
`393
`
`393
`Efl‘icacy
`Dose Volume
`
`394
`
`Other Issues
`
`394
`
`Conclusions
`
`References
`
`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. Catlin and Carol A. Gatlin
`
`Formulation Development
`Preformulation
`402
`
`Formulation-
`
`404
`
`Focus on Osmolah’ty, Cosolvents, Oils. and pH 410
`
`pH 415
`
`371
`
`372
`
`379
`
`380
`
`381
`
`382
`
`393
`
`395
`
`395
`
`401
`
`402
`
`AstraZeneca Exhibit 2079 p. 11
`
`

`

`xii
`
`Im‘ectable Drug Development
`
`Post-Formulation Procedures
`
`pH. Additives, and Solvents
`
`418-
`
`Devices and Physical! Manipulation?
`
`41?"
`
`References
`
`Index
`
`416
`
`420
`
`423
`
`Astra-Zeneca Exhibit 2079 p.. 12
`
`

`

`2
`
`Pain, Irritation, and Tissue
`Damage with Injections
`
`Wolfgang Klement
`
`Department ofAnesthesiology and Intensive Care
`Ev. Jung—Stilling—Hospital
`Siegen, Federal Republic of Germany
`
`MUST INJECTIONS HURT?
`
`Parenteral administration of drugs is common in medical practice, eSpe-
`cially for drugs with little or no bioavailability following gastrointestinal
`absorption, with more rapid onset times than possible with oral adminis-
`tration, or with desired local effects. Since needles are used to penetrate the
`skin, some amount of pain is tolerated by the physician [who does not feel
`it) and by the patient (who preferably wants to get help]. Pain, however, is
`an essential sensation warning the organism against possible tissue dam—
`age. Scrutiny of knowledge about the possibility of irritation and damage
`with certain drugs and their formulations reveals that the physician’s
`knowledge of irritation and damage is often small compared to the in—
`
`creasing numbers of injections and infusions he or she applies.
`This chapter's point of view derives from the author’s experiences
`with years of intravenous (IV) administration of infusions and anesthetic
`drugs with relatively high incidences of pain, itching, edema, and throm-
`botic complications; often, there is little knowledge about the underlying
`mechanisms and tolerance of the “usual” problems. Anesthesiologists, in
`particular, are confronted with problems associated with injections, espe-
`cially with IV routes, for the following reasons:
`
`-
`
`Anesthesia, regional or general, is usually performed through an IV
`line.
`
`15
`
`AstraZeneca Exhibit 2079 p. 13
`
`

`

`16
`
`miserable Drug Development
`
`-
`
`By means of their daily training, anesthesiologists are considered
`"IV Specialists” and are often called in case of problems with IV
`lines and administration.
`
`0 Most ofthe anesthetic drug formulations, minimally, have the po-
`
`tency to evoke pain.
`
`-
`
`Thus, most of the studies dealing with pain and discomfort on injection are
`related to data from anesthesia-related drugs.
`Systematic studies in humans about serious sequelae of injections are
`lacking. This may be due to ethical reasons or to the scarcity of such com-
`plications, since new drug formulations have. been tested extensively in an-
`imals before administration in humans is allowed. Nevertheless, there are
`
`numerous case reports dealing with thrombotic complications, tissue dam-
`age, and necrosis after drug injections. This helps us keep in mind that
`pain, irritation, and damage are still problems with inj ectable products and
`that we must not diminish our efibrts to design safer drug formulations.
`
`MECHANISMS OF PAIN AND DAMAGE
`
`From a theoretical point of View, there are a number of factors that can lead
`to pain and damage.
`Pain is mediated by the stimulation of nociceptors, which are spread
`
`throughout the whole organism in different densities, Nociceptors can be
`stimulated by strong mechanical pressure,
`low or high temperatures,
`and/or chemical irritants. The possible chemical agents are numerous and
`
`may he released from noxious cellular damage (e.g'., potassium and hydro-
`gen ions, adenosine triphosphate IATPD or they may be a chain link in the
`inflammation cascade that takes place after a noxious stiinulus (e.g.,
`kinines, histamine, serotonin, etc; see Figure 2.1).
`Thus, injections may cause pain mechanically by forcing a nonfitting
`volume of iniection into tissue. or a small vessel, by low (< 20°C) or high
`[> 40°C) temperature of the injected solution, or by chemical activation'ldi—
`rectly or by causing cellular damage). Remember that pain not only warns
`of possible tissue damage, but that serious and noxious stimuli also cause
`the nociceptors to release mediators for starting the inflammatory cascade
`[e.g., substance P, calcitonin genearelated peptide, etc), which. in turn
`causes weal, flare reaction, and edema. in sum, chemical irritants may
`cause not only pain but also morphological changes like inflammation via
`excessive stirriulation of nociceptors.
`Cellular and tissuo damage-can be caused by cellular or tissue specific
`toxicity or by aggressive physicochemical properties [e.g., acidity, basicity,
`high or low osmolality) leading to cellular membrane destabilization.
`In both cases, the extent of possible damage depends on the local peak
`concentration of the irritant, as well as on the time course of local
`
`AstraZeneoa Exhibit 2079 p. 14:
`
`

`

`
`
`Pain, Irdtaticn, and Tissue Damage with Injections
`
`17
`
`
`
`Figure 2.1. Interactions of ncciceptor, tissue, and vessels during
`inflamation following trauma.
`
`INFLAMMATORY REACTION
`
`hradykluin
`leukotrienes
`Delmarpha-
`
`nuclear
`
`macro bases
`
`
`
`
`TEA
`
`A
`
`
`
`histamine, mam blond flow,
`serotonin
`annulary
`
`_
`Interleukin-5
`
`prosta—
`
`z‘gfir‘ar‘ediator release
`‘
`' (e.g., substance P,
`
`-
`NGF
`
`vessels
`
`
`
` direct stimulation
`
`Trauma causes cellular damage and thus direct and indirect noxious stimulation of
`the nociceptor. The mediators released by the activated nociceptor start the
`inflammation cascade, leading to an increase in nociceptor activation, mediator
`release, and vascular and tissue reactions.
`
`
`concentration. The peak concentration in the tissue or blood is determined
`by the concentration and volume of the injection and the speed of injec-
`tion. Immediate processes like dilution in blood, local binding (e.g., pro-
`teins, fat), enzymatic degradation, and chemical reactions all contribute to
`the effective peak concentration during injections.
`The time course of local concentration depends on the distribution
`(diffusion) of the substance in the tissue and the velocity of chemical reac—
`tions with the surrounding tissue. This, in turn, depends on the supply of
`reacting substances and thus is often determined by local blood flow. Thus,
`the possibility for serious sequelae is highest with injections of noxious for-
`mulations designed for specific areas into the wrong area (e.g., solutions
`for artery embolization of arteriovenous malformations into the wrong ves—
`as] or paravascularly; paravascular administration of chemotherapy; injec-
`tion of a solution for an intramuscular [1M] route into subcutaneous fat).
`
`Various kinds of allergic reactions can also cause complications, both
`at the site of injection as well as systemically. The reason for damage is
`
`AstraZeneca Exhibit 2079 p. 15
`
`

`

`18
`
`Injectable Drug Development
`
`based on the molecular structure of all substances. Aspects of a drug for—
`mulation other than the actual drug (Vehicles, diluents, stabilizers) are also
`able. to cause allergic reactions. This mixture should be tailored to the pa—
`tient’s disposition and allergies. In most cases, local reactions are moderate
`and transient. Therefore, allergic reactions will only be discussed when
`their likelihood is high or there is a possibility for severe damage.
`This chapter presents an overview of the problems and sequelae that
`can occur using different routes of injection, primarily IV. Certain drugs
`and formulations will serve as examples (where possible sequelae with in—
`jections were observed and studied]. If known, reasons and mechanisms
`for pain, irritation, and damage are described, and suggestions are pro~
`
`vided to prevent possible damage.
`
`ROUTES OF DRUG INJECTION
`
`Cutaneous/Subcutaneous Injections
`
`Subcutaneous and, in particular, paravascuiar injections have been per—
`formed where inh‘avascular injections were intended. Since it is unclear
`whether or not inattentive paravascular injections will occur with incorrect
`needle positiou exclusively, this problem is discussed later.
`Subcutaneous injections are done more frequently into tissues with
`relatively low blood flow like fat and connective tissue. On the one hand,
`this would hopefully produce the desired effect of slow absorption and
`longer duration of action. Irritant drug formulations, on the other band,
`
`also form long acting subcutaneous deposits and stay in contact with the
`tissue, vessels, and nerve fibers, slowly decreasing in concentration. There-
`fore, the theoretical possibility of causing damage is high, and this is the
`reason that some drug formulations designed for injection into the muscles
`with a good blood supply may cause severe damage when injected into
`subcutaneous fat.
`
`A review of possible cutaneous reactions to injectables was published
`recently Morgan 1995a; Morgan 19951)). It included special aspects of skin
`pathology and histopathology‘. In most of the cutaneous and subcutaneous
`injections three groups of drugs were administered: insulins, heparins, and
`local anesthetics. Therefore, these drugs will serve as examples for seque—
`lae of cutaneous injections for the following discussion.
`In the case of insulin, local reactions to injection are frequently im-
`munologic problems. In early formulations, pain, itching, flare, edema, and
`indurations occurred in more than 50 percent of the patients during ther-
`apy. These preparations were impure and acidic (pi-I 3.5), which may ex—
`plain the high incidence of allergic reactions and pain on injection. The
`incidence of allergic reactions decreased with highly purified insulins
`and is minimal with human insulin produced using recombinant DNA
`
`AstraZeneca Exhibit 2079 p. 16
`
`

`

`Pain, Irritation and Tissue Damage with Injections
`
`‘19
`
`(deoxyribonucleic acid) technology (Goldfine and Kahn 1994). Since the in-
`cidence of latex allergies seems to be increasing, care should be taken that
`the sealing compounds of vista and syringes used in insulin therapy do not
`contain rubber. This may exert an allergic reaction that does not depend on
`insulin allergy (Towse et al. 1995). A special case of damage to the cutis and
`subcutis is caused by insulin-induced lipatrophy, which occurs with re-
`peated injections at the same injection site. The incidence is said to be up
`to 3 percent in adults and even higher in children. The underlying mecha—
`nism is thought to be immunologic (Reeves et al. 1980]. The addition of cor-
`ticosteroids (Kumar et al. 1977), use of highly purified insulins, regular
`change of injection site, and intramuscular administration should prevent
`its development.
`With Subcutaneous heparin injection, 3 heparin-induced skin necrosis
`may occur days after the drug administration (starting with edema, flare,
`and pain at the injection site) and lead to necrotic lesions of the cutis and
`subcutis. An impressive image of such a reaction was recently published
`[Christiaens and Nieuwenhuis 1996). This complication is rare and its
`
`causes are unknown, but the delay between first injections and necrosis
`does not indicate a direct chemical reaction to the drug formulation. Since
`
`heparin—induced skin necrosis is often accompanied by thrombocytopenia,
`it may represent a localized form of the hep arm-induced thrombocympenia
`syndrome (Mar et a1. 1995] and cause local thrombotic lesions of small ves-
`sels followed by tissue necrosis.
`Local anesthetics, usually administered intra— or subcutaneously for
`minor surgical procedures, were known to cause pain on injection, espe-
`cially in the case of lidocaine. That pain on inj ection occurs with the appli~
`cation of local anesthetics, which the patient is told will minimize his or her
`pain during surgery, does not help improve the patient’s confidence in
`modern medicine. Numerous studies have been performed. examining how
`to avoid pain on injection (see Table 2.1).
`Since the pH of various formulations of lidocaine varies between 4- and
`5 (author’s unpublished data; Lugo—Janer et al. 1993], the acidity was be-
`lieved to cause pain, thus, the solutions were buffered, usually with small
`amounts of 8.4 percent'sbdium bicarbonate. With the use of buffered ver-
`sus plain Iidocaine, the intensity of pain on intra- and subcutaneous injec—
`tion decreased by 40 to 80 percent (Brogan et al. 1995,- Matsumoto et al.
`1994; Christoph et al. 1988). Similar results were obtained with buffered li-
`docaine in digital nerve blocks (Bartl‘ield et al. 1-993], buffered prilocaine in
`IV regional anesthesia (Armstrong et al. 1990), and intracutaneously in—
`jected buffered mepivacaine (Christoph et al. 1988).
`Some authors tried to use warmed plain lidocaine (37 to 40°C) to min-
`
`imize pain on injection. While pain intensity sometimes decreased by 40 to
`70 percent (Brogan et al. 1995; Davidson and Boom 1992), others failed to
`evoke beneficial effects with warming [Mader et al. 1994,- Dalton et al.
`1989). Buffered lidocaine provoked the same low pain intensity with 37°C
`
`AstraZeneca Exhibit 2079 p. 17
`
`

`

`20
`
`Im'ectable Drug Development
`
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`
`
`
`
`
`
`
`

`

`Pain, irritation and fissue Damage m'th Infections
`
`21
`
`rather than 20°C (Martin et a1. 1996), but others described no benefit of
`
`warming or buffering except when lidocaine was warmed and buffered
`[Mader et a1. 1994]. To add further to the confusion, saline solutions of li-
`docaine with a pH of 4.2 and 5.3 evoked less pain than buffered lidocaine
`with a pI-l of 8.4- (Lug‘o—Janer et al. 1993]. In the latter study. however, only
`solutions with epinephrine were used, and its possible pain-evoking [or in-
`creasing) properties may have contributed to the confusion.
`The reason for the painful injections is not easy to determine. None of
`the pain—reducing methods deacribed. before is able to make the injections
`painless. Although intra— and subcutaneous injections cause some pain
`mechanically by distracting the. tissue [which may explain the pain occur—
`ring even with buffered local anesthetics), it remains. unclear whether or
`not the substances themselves cause pain. Controlled studies using a
`placebo (i.e., pain testing with dermal injections of pure buffered diluent
`versus buffered diluent with local anesthetic] have not been performed
`
`with two exceptions:
`
`‘l.
`
`2.
`
`Lugo—Janer and colleagues [1993) tested bacteriostatic saline so-
`lution with epinephrine 1300.000, which was found to be signif—
`icantly less painful on intradermal infiltration than lidocaine with
`epinephrine 12100300 with sodium bicarbonate 80 meq/mL. Un-
`fortunately, two different amounts of epinephrine were used,
`thus decreasing the amount of information on lidocaine’s intrin—
`
`sic pain—evoking properties.
`
`In conuast. Farley and associates (1994) found more discomfort
`with the injection of normal saline than with lidocaine in normal
`saline, which goes against its pain-evoking properties. UnfOrtu-
`nately, their preparation of normal saline had an acid pH of 4.8
`versus a more normal pH of 6.5 with lidocaine in saline. There-
`fore, the acid pH of the preparations, not the local anesthetics.
`seem to evoke the pain with dermal injections.
`
`Thus. pain on intra- and subcutaneous injections of local anesthetics is
`common. is hicompatible with the idea of local anesthetics, depends in all
`likelihood on acid pH values, and thus can be avoided by buffering the drug
`solutions. which apparently does not affect the numbing activity.
`Severe local reactions like skin necrosis. however, are rare. Allergic re-
`actions. especially with local anesthetics of the esther type did occur. The
`systemic immediate type reactions can be serious and require immediate
`treatment. Local reactions were transient and usually did not cause lesions.
`
`Vasoactive additives like epinephrine may cause tissue damage, especially
`when applied in ear lobes or digits. The cause for necrosis is a long-lasting
`vasoconstri'ction and, therefore. is most liker due to ischemia. This type of
`
`necrosis is not related to local anesthetics but to alpha—adrenergic actions
`of vasoconstrictors. It may also happen following accidental application of
`
`Asnacheoa Exhibit 2079 p. 19
`
`

`

`22
`
`Infectable Drug Develbpment
`
`such drugs, and serious sequelae can be prevented by immediate treatment
`with alpha-adrenergic blocking agents like phentolamine (Hardy and Agos—
`tini 1995).
`
`Intramuscular Injections-
`
`IM injections were widely used for more than .a century and—compared
`to IV administration—were thought to be less harmful and equally reliable
`in effect. The development of methods to measure drug concentrations in
`blood, however, revealed interindividual as well as interdrug differences
`in bioavailability (Koch—Weser 1974a, b]. Since this time, and paralleled by
`the deveIOpment of better materials and techniques of IV application, IM
`injections may not be used as often clinically. Nevertheless, many drugs are
`still injected intramuscularly, e.g., analgesics and antibiotics, and some
`problems do occur with this route of application. Due to the blood flow
`through skeletal muscle, injection concentration in the tissue decreases
`more quickly than in subcutaneous fat, with poor blood supply. But dura-
`tion of contact of the concentrated injection to the tissue is long, when com-
`pared to IV injections with rapid dilution by blood.
`Although skeletal muscle is poorly innervated nociceptively, pain is
`
`frequent with intramuscular injections, and the reasons for this have been
`studied for years (Travail ‘1955;Taggart 1972]. Research has shown that so-
`lutions with pH levels far above the physiologically tolerable range, and
`with high or very low osmolality give rise to pain on injection. The volume
`of the injection relates to pain intensity, so that, in addition to chemical ac-
`tivation, muscular nociceptors obviously reapond to tissue distention. The
`size and cut of the needle used also contribute to pain on intramuscular in-
`jection. The nerve fibers stimulated by the needle, however, seem to be lo-
`cated in the skin and in subcutaneous connective tissue, since this type of
`pain can be reduced by local cooling. Adding local anesthetics to the injec-
`tion has been recommended for pain relief, but are not used very often.
`Digital pressure applied to the region immediately before intramuscular in-
`jection reduced pain intensity by 3? percent (B'arnhill et a1. 1996}.
`Damage to muscle cells seems to occur with each intramuscular injec-
`tion, leading to measurable elevations in serum creatine kinase (CK) con—
`centrations. Numerous studies reported this nuisance in the diagnostic use
`of the enzyme in patients after intramuscular injections. Direct muscle tox-
`icity of drugs, the distention trauma, the effects of certain drugs on cell
`membrane permeability, and other mechanisms were all accused of being
`responsible for enzyme release-
`One ingenious study related the dimansion of muscle damage to the
`physicochemical. data of the injection (Sidell et a1. 19H]:
`
`- With injection of constant volumes, (SK-response depends on the
`concentration of the drug and the osmoiality of the solvents.
`
`AstraZeneca Exhibit 2079 p. 20
`
`

`

`Pain, Irritation, and Tissue Damage with Injections
`
`23
`
`injections of saline above an osmolality of 1.5 osmol/L increased
`GK activity in a concentration dependant manner up to 160 mil!
`mL with 3.2 osmoUL.
`
`0
`
`Some drugs/solvents may have their own muscle toxicity, since
`osmolalityfeffect curves differ between substances and vehicles.
`e.g., pralidoxime chloride with an osmolality below 2.0 osmollL
`increased CK activity to the same level as an equal volume of
`saline with an 05mola1ity of 3.2 osmol/L.
`
`it With the injection of constant concentrations, CK response was
`related to the injected volume, is, the total dose.
`
`I Muscle activity after an IM injection increased the CK response.
`
`This local cellular