Topical drug delivery to the posterior segment of the eye: Dexamethasone concentrations in various eye tissues after topical administration for up to 15 days to rabbits

Delivering drug to the back of the eye remains a challenging task owning to the anatomical and physiological barrier of the eye. Today injection and implants are routinely used to treat diseases in the posterior segment of the eye. Both methods require repeated injection or insertion with potential complication such as retinal detachment, endophtalmitis and retinal haemorrhage, a better non-invasive approach is therefore needed. The aim of this study was to investigate if topically applied dexamethasone in cyclodextrin micro-suspension could deliver dexamethasone to the posterior segment of the eye in therapeutic concentrations in rabbits. Un-anesthetized pigmented rabbits were used in this study where they received eye drop in the left eye and were sacrificed 1, 2, 6 h after administration, and 7 and 15 days after receiving eye drop to the left eye 3 times a day. The result showed that dexamethasone was detectable in all ophthalmic tissues tested and at relatively high concentrations in tissues at the back of the eye. Furthermore, dexamethasone did not accumulate in the ocular tissues after multiple daily dosing for up to 15 days. This novel delivery technique could therefore be used to deliver lipophilic drug to the posterior segment of the eye.