Sustained release matrix tablet of 100 mg losartan potassium: Formulation development and in vitro characterization

Sustained release matrix tablets of 100 mg losartan potassium HCl were fabricated with two release retarding polymers namely HPMC K100 M and affinisol by direct compression method. Nine trial formulations were prepared by varying content of these polymers, each from 50 mg to 100 mg; keeping the total weight of the tablet 310 mg. The best formulation was selected based on in vitro drug release profile for 12 hours conducted in Type II dissolution apparatus at 50 rpm and water as dissolution medium. Pre-compression parameters such as bulk density, tap density, Carr's index and Hausner ratio were evaluated for the selected tablet. The tablets were subjected to thickness, weight variation test, drug content, hardness and friability. Drug release kinetics, surface morphology and accelerated stability study were investigated for that selected formulation. Formulation F4 with the composition of 75 mg HPMC K100M and 100 mg affinisol was selected as the best formulation that extended the drug release up to 12 hours. Pre-compression parameters and other tableting properties were within the Pharmacopoeia limit. Release kinetics analysis proved non-fickian zero-order drug release and that was further confirmed by surface morphology of the tablets before and after dissolution study visualized by SEM. The developed formulation was found to be stable for one month stored at 60 degrees C.