A Brief Insight into Rational and Novel Approaches to Ocular Drug Delivery

As an isolated organ, eye is very difficult to study from a drug delivery point of view. Ophthalmic drug delivery is extremely interesting and highly challenging endeavours. In recent scenario, most eye-diseases are treated with topical application of eye-drops. But these conventional eye-drops have two major problems. 1) It needs frequent administration at every 4 hours or 1 hour if the infection is severe and 2) Formation of crystalline deposits on cornea due to its pH-dependent solubility which is very low. In order to provide the solution to above problems many new formulations have been developed, which include nanosuspension, nanoemulsion, inserts, hydrogels, in-situ gel, etc. The poor bioavailability of ophthalmic solution caused by dilution and drainage from the eye can be overcome by using in-situ forming ophthalmic drug delivery system prepared from polymers that exhibit reversible liquid-gel phase transition. The developed formulation provides better drug product effectiveness, reliability, stability, safety, non-irritancy and prolonged release. Thus, it’s a viable alternative to conventional eye-drops by virtue of its ability to enhance bioavailability through its longer pre-corneal residence time & ability to provide prolonged drug release upto 8 hours. The main important factor is the reduced frequency & the ease of installation resulting in better patient acceptance. Keywords: Ophthalmic delivery, in-situ gel, polymers, liquid-gel phase transition, pre-corneal residence time, prolonged drug release.