ABSTRACT
Posurdex, a dexamethasone posterior segment drug delivery system for intravitreal use, consists of dexamethasone combined with a biodegradable polymer that allows gradual release of the drug as it hydrolyses. The release of dexamethasone depends on its diffusion through the polymer matrix, the solubility of the polymer, and the rate of degradation of the polymer matrix. Potent corticosteroids such as triamcinolone acetonide, fluocinolone acetonide and dexamethasone can be very effective in these cases, but the clinician must be alert to the potential toxic effects after prolonged systemic administration. Site-specific delivery of the drug in the vitreous cavity may be able to achieve a high concentration and eliminate these systemic side-effects. Given the concerns of glaucoma and cataract associated prolonged steroid treatments in the clinical scenario of persistent macular edema, a drug delivery system that can achieve therapeutic drug levels for a moderate period may potentially be more desirable than reservoir implants, which release the drug for 2–3 years.
