The aim of this work is to develop topical hydrogels containing diclofenac potassium (DP) at 1 % w/v concentration using conventional hydrophilic hydroxypropyl methyl cellulose (HPMC, 50cPs) and different grades of modified hydrophobic hydroxypropyl methyl cellulose (HPMC, 60L, 60M, 90L and 90 M grade). Small quantity of hydrophobic HPMC is good enough to prepare gel of satisfactory quality. Hydrophobic formulations of higher viscosity with small quantity of polymer show higher release compared to hydrophilic formulations of lower viscosity with higher polymer concentration. Kinetic analysis of in vitro release profile was done by comparing the goodness-of-fit of some empirical/ semi-empirical and statistical models. From the accuracy point of view, direct fitting is preferred to transformed linear fit methods. Further, it was observed that the log-logistic distribution was the best fit for hydrophobic formulations. For hydrophilic ones, the semi-empirical models and Weibull distribution worked best, although log-logistic also showed a close fit. Hydrophobic formulations with enhancers are found to have the most promising anti-nociceptive activity.
