Formulation and Evaluation of Sustained Release Bilayer Tablets of Verapamil Hydrochloride and Enalapril Maleate

The present study is aimed to develop a sustained release bilayer tablet of a combination of Verapamil hydrochloride and Enalapril maleate which possess synergistic effect in mild to moderate hypertension in the doses 240 mg and 10 mg respectively. The tablets of both the drugs were formulated by direct compression method individually using different ratios of the controlled release hydrophilic polymers such as HPMC K100 and Carbopol 934. All the tablets were subjected to post-compression evaluation parameters such as hardness, friability, weight variation, thickness and drug content and were found to be within the limits. In vitro studies of the formulated tablets were performed in acid buffer pH 1.2 for first 2 hrs and phosphate buffer pH 6.8 for the remaining hours. The optimised formulations of both the drugs (VH 1& EM 6) which showed release upto 24 hrs were selected for compression into bilayer tablets and post compression studies were evaluated which were found to be comply with the standards. The in vitro drug release data was fitted into various kinetic models which showed that the drug release follows zero order release and the best fit release kinetics was achieved with the Korsmeyer - Peppas model.