Treatment of diseases of the eye with mucoadhesive delivery systems

Abstract Delivery of drugs to the eye is complicated by the efficient removal mechanisms in the precorneal area which serve to maintain a good refractive surface. The absorption of drugs into the eye requires a prolonged precorneal residence time and good corneal permeation. However, for most drugs corneal permeation is low. Since the precorneal drug concentration acts as the driving force for passive diffusion, the corneal epithelium and conjunctival membranes act as reservoirs for potential absorption into the eye and surrounding structures. However, the ability to increase the size of the precorneal reservoir by increasing tear film thickness with viscolysers or by increasing the time of residence with sticky immiscible ointments is unsatisfactory due to changes in visual acuity produced by refractive changes or blurring. The mucus layer covering the cornea and conjunctiva is an important target to improve drug retention by mucoadhesion of a polymer excipient, especially one that specifically attaches to the corneal rather than to conjunctival mucin. The attached polymer-mucin bond can then be used to entrap soluble, colloidal and particulate material on the eye surface.