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H Kim, J Baffi, N Collins, M Fronheiser, g Byrnes, KG Csaky, P Yuan, RJ Lutz, R Dedrick, MR Robinson; The Ocular Distribution of a Lipophilic Fluorescent Compound Released in the Subconjunctival Space from a Sustain-Release Device in the Rat . Invest. Ophthalmol. Vis. Sci. 2002;43(13):2303.
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Purpose: Pharmacologic approaches using anti-angiogenesis agents may be helpful for the treatment of choroidal neovascularization. The delivery of drugs into the choroid and subretinal space may be safer and more effective using sustained-release implants placed in the subconjunctival space versus surgical implantation directly into the vitreous cavity. We investigated the ocular distribution of a lipophilic fluorescent compound, 5-hexadecanoylaminofluorescein (H-110, MW= 586), from a sustained-release device placed in the subconjunctival space to determine the feasibility of using this approach for drug delivery into the vitreou Methods: We used the lipophilic fluorescent compound to construct sustained-release matrix implants to produce slow rates of drug release for a prolonged period time. Three types of matrices were formed by combining the compound with either polyvinyl alcohol, hydropropyl cellulose (HPC), or silicone. The in vitro release rates of the three different implant designs were determined. The implants, made into 1.5mm flat discs, were surgically placed in the subconjunctival space of Brown Norway rats. The animals were sacrificed periodically up to 1 week post-implantation, enucleated, and frozen sections of the globes were done. The slides were examined using a fluorescent microscope. Results: The in vitro drug release from the implants showed characteristic matrix device behavior in which the accumulated amount of H-110 released increased as . All three implant designs released the lipophilic fluorescent compound (H-110) rapidly into the surrounding substantia propria and underlying sclera. Significant amounts of H-110 in the choroid and subretinal space were detected only in the eyes receiving the most rapidly releasing implant (HPC matrix design). Conclusion: The choroid was a formidable barrier to the passage of a lipophilic fluorescent compound into the vitreous cavity from a sustained-release device placed in the subconjunctival space of the rat. This may be due to the rapid clearance of the drug from the blood flow in the choroid and/or to the limitation of lipophilic compounds to penetrate a partial aqueous barrier.
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