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K. Okabe, H. Kimura, J. Okabe, A. Kato, N. Kunou, M. Nozaki, Y. Ogura; Intraocular Tissue Distribution of Betamethasone following an Intrascleral Implantation of Sustained Drug Delivery Device . Invest. Ophthalmol. Vis. Sci. 2003;44(13):4430.
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Purpose:To evaluate the tissue distribution of betamethasone (BM) after implantation of a non-biodegradable polymeric intrascleral implant as a new controlled intraocular delivery system. Methods: Intrascleral implants designed to release BM for at least 1 month were placed in the sclera of pigmented rabbits. The BM concentrations in the aqueous humor, vitreous, and retina/choroid were determined by high performance liquid chromatography (HPLC) at weeks 1, 2, and 4 after implantation. The BM concentrations in three sections of retina/choroid were also investigated. Retinal toxicity was evaluated by electroretinography and histological examination. Results: The BM release from the intrascleral implant in vitro and in vivo showed zero-ordered release profiles for 4 weeks. The BM concentrations in the retina/choroid after implantation of the intrascleral device remained higher than the effective concentrations for suppressing various inflammatory processes for at least 4 weeks. The BM concentrations in the retina/choroid around the implantation site were over 10 times higher than in the opposite side and the posterior pole throughout the study. No substantial toxic reactions were observed by electroretinography or histologic study. Conclusions: These findings suggested that the polymeric intrascleral implant could be a useful drug carrier for intraocular delivery of BM without producing severe retinal toxicity. The implantation site might be determined in consideration of the intraocular drug distribution after implantation.
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