FORMULATION, EVALUATION AND IN VITRO DISSOLUTION PERFORMANCE OF ENALAPRIL MALEATE SUSTAINED RELEASE MATRICES: EFFECT OF POLYMER COMPOSITION AND VISCOSITY GRADE.

The present study aimed at developing the sustained release matrix tablets of enalapril maleate and evaluating the effect of polymer concentration and viscosity grade on drug release. The sustained release enalapril maleate tablets were successfully formulated by direct compression method using nonionic cellulose ethers HPMC K15, HPMC K100 and HPC polymers either alone or in combination. In-vitio drug release study was carried out in phosphate buffer (pH 6.8) for a period of 24 h following USP dissolution apparatus II i.e., paddle apparatus. Model dependent approaches like zero-order, first order, Higuchi's model and Korsmeyer-Peppas model were used to assess drug release from various formulations. All the three polymers alone or in combination sustained the drug release. The drug release characteristics from HPMC and HPC polymer followed zero order release kinetics except for 45% concentration of all polymers alone or in combination where by the drug release followed Higuchi's model. In all cases, the drug release mechanism was both diffusion as well as erosion.