Intraocular tissue distribution of betamethasone after intrascleral administration using a non-biodegradable sustained drug delivery device

PURPOSE. To evaluate the tissue distribution of betamethasone (BM) after implantation of a nonbiodegradable intrascleral implant as a new, controlled intraocular delivery system. METHODS. Nonbiodegradable 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 highperformance liquid chromatography (HPLC) at 3, 7, 14, and 28 days after implantation. The BM concentrations in three sections of retina-choroid were also investigated. Retinal toxicity was evaluated by electroretinography and histology. RESULT. The BM released 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 placement of the intrascleral implants remained higher than effective concentrations for suppressing various inflammatory processes for at least 28 days, The BM concentrations in the retina-choroid around the implantation site were more than 10 times higher than in, e opposite side throughout the study. No substantial toxic reactions were observed by electroretinography or histology. CONCLUSIONS. These findings suggested that the nonbiodegradable intrascleral implant could be a useful drug carrier for intraocular delivery of BM without producing severe retinal toxicity. The intrascleral site may be considered for effective intraocular drug distribution after implantation.