A REVIEW ON TOPICAL OPHTHALMIC DRUG DELIVERY SYSTEMS
Optimum bioavailability can be achieved when just enough cyclodextrin (< 15%) is added to the aqueous eye. drops solution to solubilise the lipophilic water insoluble drug15. But lncreased concentration will result in decrease in bioavailability. 6. Bioadhesive polymers: The bioadhesive polymers16 adhere to the mucin coat covering the conjunctiva and the comeal surfaces of the eye, thus prolonging the residence time of a drug in the conjunctival sac. These polymers can be neutral, synthetic or semi synthetic. Polyacrylic acid, polycarbophil and hyaluronic acid are synthetic polymers commonly used. Chitosan is a bioadhesive vehicle suitable for ophthalmic formulation since it exhibits general biological properties such as biodegradability, nontoxicity and biocompatibility. Due its positive charge at neutral pH and ionic interaction with the negative charges of sialic acid occurs. Xanthan and carrageenan are also described as bioadhesive polysaccharides17. ENHANCEMENT IN CONTROLLED DRUG-DELIVERY It is realized that the preferred system of ophthalmic delivery would provide improved bioavailability, site-specific delivery and with continuous drug release. So achievements have been made in the following areas: 1. In situ forming gels: The progress has been made in gel technology lip the development of droppiable gel. They are liquid uponjnstillation and undergo phase transition in the ocular cul-de-sac to form visco-elastic gel and this provides a response to environmental changes18.Pages: 1 2 3 4 [5] 6 7 8 9 10 11 12 13 14
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20.02.2010
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