Asian Journal of Chemistry Vol. 22, No. 3 (2010), 2147-2154 Methyl Cellulose Based Sustained Release Thermosensitive in situ Fast Gelling Ocular Delivery of Ketorolac Tromethamine MANAS BHOWMIK*, SANCHITA DAS, JAYDEEP SINHA, SWARNENDU BAG, DIPANKAR CHATTOPADHYAY† and LAKSHMI K. GHOSH Pharmaceutics Research Lab II, Department of Pharmaceutical Technology, Jadavpur University, Kolkata-700 032, India Tel: (91)(433)343278; E-mail: b.manasju@gmail.com The purpose of this study is to develop methyl cellulose (MC) based in situ gelling formulations of ketorolac tromethamine (KT) for enhan- cing its ocular bioavailability. The gelation temperature of 1 % w/v MC solution was 60 ºC. Sodium chloride was added to reduce the gelation temperature of MC solution below physiological temperature, i.e., 37 ºC. The effect of NaCl concentration on the rheological property and drug release profile of prepared formulations were examined. It was observed that 5-7 % w/v NaCl lowered the gelation temperature below 37 ºC and the solution was free flowing liquid at 25 ºC for proper instil- lation to the eye as drop (s) and gave sustain drug release profile. In an attempt to increase drug release time by increasing viscosity of gel at 37 ºC without compromising the in situ gelation capability, hydroxy propyl methyl cellulose (HPMC K15 M) was added, replacing MC that gave finally 1 % w/v polymer (MC and HPMC mixture) solution contai- ning 0.5 % w/v KT. The viscosity and drug release profile of prepared formulations containing HPMC were evaluated. The highest viscosity at 37 ºC and slowest drug release was obtained from MC:HPMC::2:1 solution containing 7 % w/v NaCl. Key Words: Methyl cellulose, Hydroxy propyl methyl cellulose, Ketorolac tromethamine, in situ Gelling, Sodium chloride. INTRODUCTION Poor bioavailability of conventional ophthalmic liquid formulation is caused by the rapid elimination of drug through lacrimal secretion and normal tear turnover 1-3 . Ocular bioavailability can be significantly improved by increasing precorneal resid- ence time of drug 4,5 or by instillation of concentrated drug solution 6 . To increase the ocular residence time of drug, many formulations were developed such as viscous solutions, ointments, gels, suspensions and inserts 7,8 . The concentrated drug solutions causes both ocular and systemic side effects 9 . This problems can be overcome by using in situ gel forming ocular drug delivery systems prepared from polymers that †Department of Polymer Science and Technology, University College of Science and Technology, 92, A.P.C. Road, University of Calcutta, Kolkata-700 009, India.