Strategies to prolong the residence time of drug delivery systems on ocular surface

Ocular diseases may be treated via different routes of administration, such as topical, intracameral, intravitreal, oral and parenteral. Among them the topical route is most accepted by patients, although it provides in many cases lowest bioavailability. Indeed, when a formulation reaches precorneal area, i.e., drug absorption and/or action site, rapidly eliminated due to eye protection mechanisms blinking, basal reflex tearing, naso-lacrimal draining. To avoid this reduce frequency dosing, various strategies have been developed prolong residence time after administration. These include use viscosity increasing mucoadhesive excipients well combinations thereof. From delivery system point view, liquid semisolid formulations are preferred over solid ocular inserts contact lenses. Furthermore, can contain nano- microcarrier systems that contribute prolonged time. Within review an overview about types their performance valid animal models clinical trials provided.