Topical dexamethasone delivery to the retina: An aqueous cyclodextrin-based microsuspension

Abstract

Topical drug delivery to the eye is challenging and with conventional eye drops only 0.07%–4% of the dose reaches the aqueous humor and less than 0.001% the retina. Consequently, all currently available drug treatments for retinal diseases are based on invasive drug administration such as intravitreal injections and inserts. Six obstacles or barriers to drug permeation from the ocular surface into the eye have been identified and characterized. This review describes how each of these obstacles was addressed through cyclodextrin-based aqueous eye drop microsuspension and how novel physiochemical formulation techniques made it possible to deliver therapeutic drug concentrations topically to the retina. Finally, it is demonstrated that the therapeutic efficacy of aqueous 1.5% (w/v) dexamethasone eye drop microsuspension in humans for diabetic macular edema is comparable to that of a 0.7 mg dexamethasone/polymer intravitreal insert.