The aim of the present investigation was to prepare extended release film coated matrix tablets of cephalexin using binary mixture of two grades of hydrophilic polymer, hydroxypropyl methyl cellulose (HPMC), by direct compression method. Results of the preliminary trials indicated that the polymers used have significant release retarding effect on the formulation. To study the effect of concentration of polymers on drug release from matrix tablets, 3(2) full factorial design was applied. The concentration of HPMC K15M and HPMC 15cps were used as independent variables, while percentage drug release was selected as dependent variable. The dissolution data were fitted into zero-order, first-order, Higuchi and Korsemeyer-Peppas models to identify the pharmacokinetics and mechanism of drug release. Comparative study of dissolution profile of final batch F3 with market preparation (Sporidex AF 375) was done by similarity factor (f(2)) determination and it was concluded that final formulation F3 (10% HPMC K15M, 17.5% HPMC 15cps) shows good similarity with the market product. The results of the accelerated stability study of final formulation F3 for 1 month revealed that storage conditions were not found to have made any significant changes in final formulation F3. The release of cephalexin was prolonged for 6 h by using polymer combinations of HPMC and a twice daily matrix tablet was formulated.
Keywords: Cephalexin; factorial design; hydroxypropyl methyl cellulose; matrix tablets; release kinetics; similarity factor (f2).