Development and Evaluation of Bilayer Tablets of Losartan Potassium

The aim of present study is to prepare bilayer tablets of Losartan Potassium with an immediate release and a controlled release layer. The immediate layer was prepared using super disintegrant sodium starch glycolate and controlled release layer is formulated with polymer guar-gum and HPMC K15M, individually in different concentrations and in combinations. The values of pre-compression parameters evaluated were within prescribed limits. (Angle of repose 17.66-26.10, Carrs index 18.05-20.17 % and hausners ratio of 1.19-1.29 indicated good flow property). Post compression parameters such as hardness were found to be 5.46 to 7.21 kg/cm2 sufficient enough to withstand the mechanical stress condition while handling. In all the formulations, the friability value is less 1 % and meets the Indian Pharmacopoeial limits. The percentage drug content of all the tablets was found to be almost are nearer to 100 %, swelling index of matrix tablets were directly proportional to the concentration of the polymer. Formulation (F5) containing combination of guar-gum and HPMC K15M showed better swelling index than that of other formulation. Invitro drug release from the controlled release layer increased with an increase in the polymer concentration because of increase in the thickness of the layer, which retarded drug diffusion out of tablets. Formulation (F5) containing combination of guar-gum and HPMC k15M in equal proportions showed the drug release up to 24hrs. Kinetic release studies of optimized formulation F5 showed zero order release.