Treatise on Ocular Drug Delivery


by

Ashim K. Mitra

DOI: 10.2174/97816080517551130101
eISBN: 978-1-60805-175-5, 2013
ISBN: 978-1-60805-347-6



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A multidisciplinary approach is increasingly being adapted by the Pharmaceutical industry to tackle several challenges in developing e...[view complete introduction]

Table of Contents

Foreword

- Pp. i-iii (3)

Patrick M. Hughes

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Preface

- Pp. iv

Ashim K. Mitra

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List of Contributors

- Pp. v-vii (3)

Ashim K. Mitra

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A Brief Overview of Ocular Anatomy and Physiology

- Pp. 3-19 (17)

Sai H.S. Boddu, Aarika L. Menees, Animikh Ray and Ashim K. Mitra

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Routes of Ocular Drug Delivery - Conventional vs. Novel Routes

- Pp. 20-41 (22)

Deep Kwatra, Ramya Krishna Vadlapatla, Varun Khurana, Dhananjay Pal and Ashim K. Mitra

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Drug Delivery to Anterior Segment of the Eye

- Pp. 42-67 (26)

Jwala Renukuntla, Sujay J. Shah, Mitesh Patel, Aswani Dutt Vadlapudi and Ashim K. Mitra

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Barriers for Posterior Segment Ocular Drug Delivery

- Pp. 68-95 (28)

Ripal J. Gaudana, Megha Barot, Ashaben Patel, Varun Khurana and Ashim K. Mitra

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Biodegradable Polymers for Ophthalmic Applications

- Pp. 96-113 (18)

Viral Tamboli, Sulabh Patel, Gyan P. Mishra and Ashim K. Mitra

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Drug Delivery Systems for Diseases of the Back of the Eye

- Pp. 114-139 (26)

Ashish Thakur and Uday B. Kompella

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Novel Strategies to Enhance Ocular Bioavailability

- Pp. 140-160 (21)

Pradeep K. Karla, Sai HS. Boddu, Ashaben Patel, Ann-Marie Ako-Adouno and Ashim K. Mitra

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Microdialysis - Utility in Establishing PK/PD Relationships in Ophthalmology

- Pp. 161-202 (42)

Kay D. Rittenhouse, Harisha Atluri, Sai HS. Boddu and Ashim K. Mitra

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Recent Patents and Regulatory Aspects on Ophthalmic Drug Delivery Systems

- Pp. 203-252 (50)

Soumyajit Majumdar, Ketan Hippalgaonkar, Tushar Hingorani and Walter G. Chambliss

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Application of Nanotechnology in Ocular Drug Delivery

- Pp. 253-284 (32)

Xiaoyan Yang, Ashaben Patel, Aswani Dutt Vadlapudi and Ashim K. Mitra

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index

- Pp. 285-291 (7)

Ashim K. Mitra

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Foreword

Therapeutic efficacy of pharmacotherapy in the eye necessitates delivering complex drug substances to sequestered active sites for the appropriate duration. Achieving this is fraught with challenges from issues of bioavailability to simple non-compliance, whether that’s due to physical limitation such as in the elderly, lifestyle factors or simply not self-administering medication. Drug delivery can greatly improve the therapeutic outcome in these cases. Moreover, in certain diseases drug delivery may not only enhance performance of an active, but is an absolute requite for function.

Despite new and novel therapies for posterior segment diseases there is still a very large unmet medical need to treat serious ocular conditions. Vision threatening back of the eye diseases such as wet age-related macular degeneration, diabetic macular edema, uveitis and geographic atrophy are leading causes of blindness. Various therapeutic classes of drugs are showing promise at a receptor or ligand level for affecting these diseases. Promising new drug substances range from antibodies, antibody fragments and peptides to aptamers and siRNAs. In the case of some drugs, such as siRNAs, the lack of an effective delivery system may prevent fulfilling the promise of an entire therapeutic class.

Unfortunately, delivering these drugs to their intended target; the choroid, RPE and vitreoretinal space remains illusory. Without new and novel drug delivery strategies, effective pharmacologic intervention in these diseases may never come to fruition. Drug delivery to the eye is multifactorial and poses significant challenges. Bioavailability to the anterior segment of the eye remains low from topical administration despite decades of research. In fact, the challenges to ocular drug delivery are becoming exponentially greater with therapies directed towards posterior segment diseases and a much broader palette of drug substances to be delivered. The present eBook not only covers these issues in significant detail, but the leading experts in the field authored the chapters. The present eBook offers an integrated understanding of anatomy and physiology, disease state, drug absorption and disposition and drug delivery.

The first five chapters of the eBook lay the foundation for ocular drug delivery and the current state of the art. Chapter 1 nicely deals with the anatomic and physiologic constraints to drug delivery. Chapter 2 explores delivery beyond conventional topical and systemic approaches. Taking advantage of non-conventional routes of delivery minimizes some of the issues with conventional topical therapy including tear dilution, rapid precorneal drainage and may also buffer systemic absorption to some extent. Additionally, these novel routes offer new and novel opportunities for sustained and controlled delivery to the eye. This chapter differentiates conventional and novel routes and discusses their relative merits. Chapters 3 and 4 deal with anterior and posterior segment drug delivery, respectively. The various attempts to improve anterior segment drug delivery are described. Static and dynamic barriers to drug delivery are discussed. A decade ago little consideration was given to the dynamic barriers to penetration as well as the role of enzymes and transporters in posterior segment drug delivery. The field is just now realizing the impact of these factors and Chapter 4 describes these critical and newly defined variables.

Specific strategies for achieving effective drug delivery to the eye are detailed in Chapter 5 through 7 and Chapter 10. In Chapter 5, biodegradable polymers for drug delivery are reviewed. This class of polymers represents a significant component of many posterior segment drug delivery strategies. Unfortunately, a detailed understanding as it relates to the eye is often missing from the ocular formulator’s arsenal. This is a crucial chapter for anyone interested in ocular drug delivery. Drug delivery in a broader context is dealt with in chapter 6 and includes erodible and non-erodible systems. Implants, microspheres, liposomes and semi-solids as well as more complex delivery systems are discussed. These strategies have been shown to be effective in circumventing many of the barriers to ocular absorption, but none are without potential side effects. Chapter 7 addresses enhancing the permeation of these barriers, rather than circumvention, through techniques such as ultrasound, microneedles and prodrug modification.

The next two chapters cover critical areas for the field. The eye is not readily amenable to serial sampling and as such it is difficult to reasonably power ocular pharmacokinetic studies. Microdialysis as a tool to address the limitations of classic ocular pharmacokinetic techniques is discussed in Chapter 8. This is a tool that will go a long way in facilitating the development of effective treatments for ocular diseases. However, getting new delivery systems approved and protected is as important as innovating new technologies. Unmet patient needs are not addressed until a drug delivery system is shown to be safe and effective in well-controlled clinical trials, approved through the relevant regulatory bodies and commercialized for use. Chapter 9 discusses US regulatory requirements and guidelines relevant to ophthalmics as well as recent patents in the field. The final chapter of the eBook, Chapter 10, discusses the exiting new area of nanotechnology in drug delivery. Nanotechnology advances such as liposomes, niosomes, nanoparticles and dendrimers among others are fully explored

The present eBook covers in significant detail the issues and resolutions with developing drug delivery systems for the eye. Moreover, key researchers in the field authored this eBook. This eBook serves as a great reference for anyone involved in treating ocular disease including: ophthalmologists and other clinicians, pharmaceutical formulation scientists, ocular pharmacokineticist and pharmacists amongst others. This reference should be in the armamentarium of any scientist serious about drug delivery to the ocular tissues.

Patrick M. Hughes
Formulations and Drug Delivery Sciences,
Allergan, Inc.


Preface

Over the last three decades, considerable attention has been paid to the field of ocular drug delivery due to challenges encountered in delivery of ocular drugs. The global market for ocular therapeutics in 2008 was approximately $ 12.5 billion, which has been rising at a constant rate of 9% every year. This result was achieved from significant research efforts provided by ocular drug delivery scientists and researchers across the globe. Despite the complex anatomy and physiology of the eye, drug delivery to this globe has been widely explored with many novel drug delivery systems, devices and newly developed technologies such as nanotechnology, iontophoresis and phonophoresis. The primary objective of this eBook is to provide a comprehensive understanding of ocular barriers and highlight current progress in the field of ocular drug delivery.

In this eBook, recent advances and developments in ocular drug delivery systems have been specifically addressed. Ocular anatomy and physiology along with a distinctive comparison between conventional and novel routes for drug delivery have been described. A detailed review on the development of liposomes, nanoparticles, implants and nanomicelles which has revolutionized drug delivery to both anterior and posterior segment of the eye has also been discussed. Novel strategies such as ocular iontophoresis, phonophoresis and transporter targeted prodrug delivery which are being currently investigated for improving ocular drug delivery have also been provided. This eBook will definitely serve as an excellent reference to all future ocular researchers and scientists striving to improve drug delivery to the eye.

Ashim K. Mitra
Division of Pharmaceutical Sciences,
University of Missouri-Kansas City,
USA

List of Contributors

Editor(s):
Ashim K. Mitra
University of Missouri-Kansas City
USA




Contributor(s):
Sai H.S. Boddu
Department of Pharmacy Practice
College of Pharmacy and Pharmaceutical Sciences, The University of Toledo
Toledo
Ohio
USA


Aarika L. Menees
School of Medicine
University of Missouri-Kansas City,
Kansas City
Missouri, 64108
USA


Animikh Ray
Division of Pharmaceutical Sciences
University of Missouri-Kansas City,
Kansas City
Missouri, 64108
USA


Ashim K. Mitra
Division of Pharmaceutical Sciences
University of Missouri-Kansas City,
Kansas City
Missouri, 64108
USA


Deep Kwatra
Division of Pharmaceutical Sciences
University of Missouri-Kansas City,
Kansas City
Missouri, 64108
USA


Ramya Krishna Vadlapatla
Division of Pharmaceutical Sciences
University of Missouri-Kansas City,
Kansas City
Missouri, 64108



Varun Khurana
Division of Pharmaceutical Sciences
University of Missouri-Kansas City,
Kansas City
Missouri, 64108



Dhananjay Pal
Division of Pharmaceutical Sciences
University of Missouri-Kansas City,
Kansas City
Missouri, 64108



Jwala Renukuntla
Division of Pharmaceutical Sciences
South College School of Pharmacy
Tennessee
USA


Sujay Shah
Division of Pharmaceutical Sciences
University of Missouri-Kansas City,
Kansas City
Missouri, 64108



Aswani Dutt Vadlapudi
Division of Pharmaceutical Sciences
University of Missouri-Kansas City,
Kansas City
Missouri, 64108



Mitesh Patel
Division of Pharmaceutical Sciences
University of Missouri-Kansas City,
Kansas City
Missouri, 64108



Ripal J. Gaudana
Division of Pharmaceutical Sciences
University of Missouri-Kansas City,
Kansas City
Missouri, 64108



Megha Barot
Division of Pharmaceutical Sciences
University of Missouri-Kansas City,
Kansas City
Missouri, 64108



Ashaben Patel
Division of Pharmaceutical Sciences
University of Missouri-Kansas City,
Kansas City
Missouri, 64108



Viral Tamboli
Division of Pharmaceutical Sciences
University of Missouri-Kansas City,
Kansas City
Missouri, 64108



Sulabh Patel
Division of Pharmaceutical Sciences
University of Missouri-Kansas City,
Kansas City
Missouri, 64108



Gyan P. Mishra
Division of Pharmaceutical Sciences
University of Missouri-Kansas City,
Kansas City
Missouri, 64108



Ashish Thakur
Department of Pharmaceutical Sciences and Department of Ophthalmology
University of Colorado Anschutz Medical Campus, Aurora
Colorado , 80045
USA


Uday B. Kompella
Department of Pharmaceutical Sciences and Department of Ophthalmology
University of Colorado Anschutz Medical Campus, Aurora
Colorado , 80045
USA


Pradeep K. Karla
Division of Pharmaceutical Sciences,
School of Pharmacy, Howard University
Washington D.C., 20059
USA


Ann-Marie Ako-Adouno
Division of Pharmaceutical Sciences,
School of Pharmacy, Howard University
Washington D.C., 20059
USA


Kay D. Rittenhouse
Translational Medicine Ophthalmology
Specialty Care Business Unit, Pfizer Inc.
New York, 10027
USA


Harisha Atluri
Xeno Port Inc. Santa Clara
California , 95050
USA


Soumyajit Majumdar
Department of Pharmaceutics
University of Mississippi
Mississippi , 38677
USA


Tushar Hingorani
Department of Pharmaceutics
University of Mississippi
Mississippi , 38677
USA


Ketan Hippalgaonkar
Department of Pharmaceutics
University of Mississippi
Mississippi , 38677
USA


Walter G. Chambliss
Department of Pharmaceutics
University of Mississippi
Mississippi , 38677
USA


Xiaoyan Yang
Division of Pharmaceutical Sciences
University of Missouri-Kansas City, Kansas City
Missouri , 64108
USA




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