Development and evaluation of sustained release matrix tablets of losartan potassium

The objective of the present study was to develop a sustained release matrix tablets of Losartan potassium, an anti hypertensive drug. The sustained release tablets were prepared by wet granulation and formulated using different drug and polymer ratios. Hydrophilic natural polymers like xanthan Gum (XG), guar gum and cellulose were used. Compatibility of the drug with various excipients was studied. The compressed tablets were evaluated and showed compliance with Pharmacopoeial limits. Formulation was optimized (F2) on the basis of acceptable tablet properties and in vitro drug release. The resulting formulation produced matrix tablets with optimum hardness, consistent weight uniformity and friability. All tablets but one exhibited gradual and near completion sustained release for losartan potassium and 90.88% released at the end of 12h. The results of dissolution studies indicated that formulation F2 (drug to polymer 1:2) is the most successful of the study and exhibited drug release pattern very close to theoretical release profile. A decrease in release kinetics of the drug was observed on increasing polymer ratio. Applying exponential equation, all the formulation tablets (except F2) showed diffusion-dominated drug release. The mechanism of drug release from F2 was diffusion coupled with erosion.