International Journal of PharmTech Research CODEN( USA): IJPRIF ISSN : 0974-4304 Vol.1, No.2, pp 164-169, April-June 2009 Review on Ocular Inserts *Rathore K. S. 1 , Nema R. K. 2 1 B.N.Girls College of Pharmacy, Udaipur,India. 2 S.D.College of Pharmacy, Muzaffarnagar-UP,India. E-mail: kamalsrathore@yahoo.com Abstract: The conventional dosage forms are account for 90% of currently accessible ophthalmic formulations. The major problem encountered is rapid precornel drug loss. To improve ocular drug bioavailability, there are significant efforts directed towards newer drug delivery systems for ophthalmic administration. Newer research in ophthalmic drug delivery systems is directed towards a combination of several drug delivery technologies, that includes to develop systems which is not only prolong the contact time of the vehicle at the ocular surface, but which at the same time slow down the elimination of the drug. Key Words: Ocular Inserts, Newer Ocular Drug Delivery System, In-Situ Gel. Introduction: Ocular drug delivery is one of the most fascinating and challenging tasks facing the Pharmaceutical researchers. One of the major barriers of ocular medication is to obtain and maintain a therapeutic level at the site of action for prolonged period of time. The anatomy, physiology and biochemistry of the eye render this organ exquisitely impervious to foreign substances. The challenging to the formulator is to circumvent the protective barriers of the eye without causing permanent tissue damage. The development of newer, more sensitive diagnostic techniques and therapeutics agents renders urgency to the development of maximum successful and advanced ocular drug delivery systems 1 . The therapeutic efficacy of an ocular drug can be greatly improved by prolonging its contact with the corneal surface. For achieving this purpose, viscosity-enhancing agents are added to eye drop preparations or the drug is formulated in a water insoluble ointment formulation to sustain the duration of intimate drug-eye contact. Unfortunately, these dosage forms give only marginally maximum sustained drug-eye contact than eye drop solutions and do not yield a constant drug bioavailability. Repeated medications are still required throughout the day 2 . These practical issues have stimulated the search for alternative methods for ocular drug delivery. Much of the work recently devoted to ocular inserts, which serves as the platform for the release of one or more active substances. It has become clear, however that the development of an ocular insert that reliably combines controlled release with absence of any irritation to the patient, poses a formidable technical challenge 3 . The conventional ocular dosage forms for the delivery of drugs are- i. Eye drops (solution, suspension) ii. Ophthalmic Ointments The eye drop dosage form is easy to install but suffers from the inherent drawback that most of the instilled volume is eliminated from the pre-corneal area 4 resulting in a bioavailability ranging from 1-10% of total administrated dose 5 . The poor bioavailability and rapid pre-corneal elimination of drugs given in eye drops is mainly due to conjunctival absorption, rapid solution drainage by gravity, induced lachrymation, blinking reflex, low corneal permeability and normal tear turnover. Because of poor ocular bioavailability, many ocular drugs are applied in high concentrations. This cause both ocular and systemic side-effects 6 , which is often related to high peak drug concentrations in the eye and in systemic circulation. The frequent periodic instillations of eye drops are necessary to maintain a continuous sustained therapeutic drug level. This gives the eye a massive and unpredictable dose of medication 7 . Suspension types of pharmaceutical dosage forms are formulated with relatively water insoluble drugs to avoid the intolerably high toxicity created by saturated solutions of water-soluble drugs. However, the rate of drug release from the suspension is dependent upon the