In-Situ Forming Polymeric Drug Delivery Systems for Ophthalmic Use: An Overview

Delivery of drug into the ocular region is hindered by the protective layers that encapsulate the eyes, it has always been a major problem to get an effective bioavailability of the active drug in the ocular region due to the low precorneal resident time of most of the ocular delivery systems specifically convention once such as ointment, solution and suspension, as a result, most of the delivery systems are not capable of effectively treating ocular diseases. Several works have and are being carried out to overcome this problem one of which is using in-situ forming polymeric systems. Ocular In-situ gelling systems are a novel class of ocular drug delivery systems that are initially in a solution form but instantaneously gets converted into a viscous gel upon introduction or installation in the ocular cavity from which the active drugs get released in a sustained manner. This sol-togel phase transition depends upon various factors like change in pH, ion presence and change in temperature. Gel formed after the transformation has preferred viscosity along with bio-adhesive property, which increases the gel’s resident time in the ocular area and also releases the drug in a prolonged and sustained manner unlike conventional eye drops and ointments. This review emphasizes various ocular in-situ systems namely, pH triggered, Ion activated, and Temperature triggered systems which have prolonged residence time in the cul-de-sac area of the eye, hence increasing the ocular bioavailability.