Collagen shield enhancement of topical dexamethasone penetration

Collagen corneal shields were investigated as a vehicle for enhancing the ocular penetration of topical 0.1% dexamethasone alcohol in rabbit eyes. Four protocols were compared: a single dexamethasone drop, hourly drops, a 24-hour collagen shield presoaked in 0.1% dexamethasone, and a presoaked collagen shield followed by hourly drops. Dexamethasone concentrations in the cornea, aqueous, iris, and vitreous were measured by radioassay at six time intervals, and cumulative drug delivery over 6 hours was calculated for each tissue. Treatment with a presoaked collagen shield plus hourly drops resulted in peak and cumulative drug delivery to the cornea, aqueous, iris, and vitreous that was twofold to fourfold higher than delivery achieved with hourly drops alone. A presoaked shield by itself yielded equivalent or superior peak and cumulative drug delivery compared with a regimen of hourly drops. Collagen shields significantly enhance topical dexamethasone penetration and may be useful for maximizing the intraocular delivery of dexamethasone and for decreasing the required frequency of topical dexamethasone administration.