Design, development and in-vitro evaluation of metoprolol tartrate tablets containing xanthan-tragacanth

The present study was undertaken to develop oral sustained release tablets of metoprolol tartrate using natural hydrophilic matrix formers (xanthan gum and tragacanth). Sustained release matrix tablets of metoprolol tartrate were prepared by using different ratios of drug, xanthan gum and tragacanth. Microcrystalline cellulose (MCC) was used as diluent. The polymer was incorporated into a matrix system using direct compression technique. All the lubricated formulations were compressed using concave punches in compression machine. Compressed tablets were evaluated for diameter, hardness, friability, weight variation and in vitro dissolution using USP dissolution apparatus-II. Different formulations were evaluated with respect to dissolution profile in 900 mL phosphate buffer (pH 6.8), 0.1 M HCl solution and distilled water for 12 h at 37 degrees C. Increasing the amount of polymer (xanthan gum) in the formulation led to slow release of drug and decreasing the amount of polymer gave enhanced release of metoprolol tartrate. The kinetic treatment showed the best fitted different mathematical models (Zero order, First order, Higuchi's and Hixson-Crowell). Most of the solid matrix formulations followed Higuchi or zero order kinetics. The formulations F1, F2, F3 and F7, F8, F9 showed maximum linearity while the formulations F4, F5, F6 were not of linear behavior. The results showed that the formulation F9 containing 30% xanthan gum and 10% gum tragacanth is the most similar to that of the reference marketed preparation.