An insight to ocular in situ gelling systems

Eye is delicate organ of body whose defence mechanism restricts entry of exogenous substances. Conventional drug delivery systems get washed off within a short period of time and results in poor ocular bioavailability. Development of in situ gel having protracted ocular residence time is one of the mile stone triumphs by pharmaceutical researcher for treatment of eye aliments. This polymeric system showed sol-to-gel phase transition by change in physiological parameters in pre-corneal area which includes pH, temperature or ionic interactions etc. Three types of in situ gels are well known based on mechanism involved in phase transition viz. temperature dependent, pH sensitive, ion activated systems. Gel formed after phase transitions have high viscosity along with bio-adhesive property, which increases resistance for instantaneous rinse off due to defence contrivance. Plus it prevents nasal-lachrymal drainage and avoids the systemic side effects. Recently, in situ gels have been vexed in amalgamation with another drug delivery system. It may include use of two or more stimuli systems together or added advantages of nano-technology. Combination of in situ gel with nano-particles is utmost remedy for ocular treatment with water insoluble drugs