Transport Barriers in Transscleral Drug Delivery for Retinal Diseases

Vol. 39, No. 5, 2007

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Transport Barriers in Transscleral Drug Delivery for Retinal Diseases
Stephanie H. Kim^{a, b}, Robert J. Lutz^b, Nam Sun Wang^a, Michael R. Robinson^c

^aDepartment of Chemical and Biomolecular Engineering, University of Maryland, College Park, Md.,
^bNational Institute of Biomedical Imaging and Bioengineering, and
^cNational Eye Institute, National Institutes of Health, Bethesda, Md., USA

Address of Corresponding Author

Ophthalmic Res 2007;39:244-254 (DOI: 10.1159/000108117)

Key Words

Drug delivery
Pharmacokinetics
Retina
Transscleral
Drug transport
Metabolism
Clearance

Abstract

Transscleral delivery has emerged as an attractive method for treating retinal disorders because it offers localized delivery of drugs as a less invasive method compared to intravitreal administration. Numerous novel transscleral drug delivery systems ranging from microparticles to implants have been reported. However, transscleral delivery is currently not as clinically effective as intravitreal delivery in the treatment of retinal diseases. Transscleral drug delivery systems require drugs to permeate through several layers of ocular tissue (sclera, Bruch's membrane-choroid, retinal pigment epithelium) to reach the neuroretina. As a result, a steep drug concentration gradient from the sclera to the retina is established, and very low concentrations of drug are detected in the retina. This steep gradient is created by the barriers to transport that hinder drug molecules from successfully reaching the retina. A review of the literature reveals 3 types of barriers hindering transscleral drug delivery: static, dynamic and metabolic. While static barriers have been examined in detail, the literature on dynamic and metabolic barriers is lacking. These barriers must be investigated further to gain a more complete understanding of the transport barriers involved in transscleral drug delivery.

Author Contacts

Stephanie H. Kim
National Institutes of Health
9000 Rockville Pike, Building 13/3N07
Bethesda, MD 20892-5766 (USA)
Tel. +1 301 435 9350, Fax +1 301 496 6608, E-Mail kimstep@mail.nih.gov

Article Information

Received: March 9, 2007
Accepted after revision: June 6, 2007
Published online: September 12, 2007
Number of Print Pages : 11
Number of Figures : 3, Number of Tables : 1, Number of References : 124

Medline Abstract (ID 17851264)

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