Prodrugs incorporated into nanotechnology-based drug delivery systems for possible improvement in bioavailability of ocular drugs delivery

Numerous systems have been designed during the past three decades to improve bioavailability of ophthalmic drug delivery, including: ocular prodrugs and nanotechnology-based drug delivery system. The former can improve the efficacy of ocular drug via enhancing corneal penetration of ocular drugs, prolonging their duration of action and/or reducing the systemic side-effects, unfortunately, some characteristics of the prodrugs, such as poorly aqueous stability, poorly aqueous solubility and severe eye irritation probably, limit their clinical practice and cannot be ignored. As we all know, nanotechnology for ocular drug delivery can carry poorly soluble drugs, protect the encapsulated molecules from hydrolysis, control the rate of drug delivery and prolong the precorneal retention of drugs. All of these merits may solve the problems in the utilization of ocular prodrugs and increase the bioavailability of ocular drug delivery. By reviewing recent advances of prodrugs and nanostructures in ocular drug delivery, this paper focus specifically on the promising prospects of nanocarriers overcoming the drawbacks of prodrugs for ophthalmic drug delivery by precorneal routes.