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The majority of eye diseases are treated with topical eye drops. The meagre bioavailability and beneficial answer exhibited by these conventional eye drops due to fast precorneal elimination of the drug may be surmount by the use of in situ gelling systems that are instilled as drops into the eye and undergo a sol-to-gel transition in the cul-de-sac. In recent years, increased attention has been given to the development of new systems for the delivery of ocular medication. A number of ocular delivery systems lengthen the extent of drug action by enhancement of corneal absorption; these include suspension, soluble gels and emulsions, hydrophilic ocular inserts, ion-pair associations, liposomes, niosomes, nanosuspension, nanoparticles and prodrugs. Other delivery systems endow with a controlled release of drugs, thus avoiding the pulse-entry with which side-effects are associated. These systems can be based on any of several different mechanisms, and include both erodible and nonerodible matrices, wafers. Timolol maleate was the first (beta)-blocker to be used as an antiglaucoma agent and to date remains as the standard because none of the newer beta blockers were found to be more effective. Timolol maleate has the longest record of safety and efficacy to lower IOP and is administered via eye drops one or more times per day. The critical step is to develop a formulation for timolol maleate that leads to sustained delivery for long time.
K. S. Rathore. B. N. Girls College of Pharmacy, Udaipur-Rajasthan, India. kamalsrathore@gmail.com
11.16 Vehicles, delivery systems, pharmacokinetics, formulation (Part of: 11 Medical treatment)