Sustained and Prolonged drug delivery approaches are very common in today’s Pharmaceutical formulation design and research work is still going on in achieving better drug product. Ophthalmic use of viscosity-enhancing agents, penetration enhancers, cyclodextrins, prodrug approaches, ocular inserts and the ready existing drug carrier systems along with their application to ophthalmic drug delivery are very common to improve ocular bioavailability. Amongst these hydrogel (insitugel forming) systems are of very important. They help to increase in precorneal residence time of drug to a sufficient extent that anocular delivered drug can exhibit its maximum biological action. The concept of this innovative ophthalmic delivery approach is to decrease the systemic side effects and to create a more pronounced effect with lower doses of the drug. Many polymers are very useful with majority of hydrogels, which undergo reversible sol-gel phase transitions in the ocular cul-de-sac to form viscoelastic gels due to phase changes of polymers in response to the physiological environment (temperature, pH and presence of ions in organism fluids. These insitu forming gels can be applied as solution and exhibit pseudo plastic behavior to minimize interference with blinking, increase precorneal residence of the delivery system and enhanced ocular bioavailability.
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