Use of Natural Gums and Cellulose Derivatives in Production of Sustained Release Metoprolol Tablets

Metoprolol tartrate sustained-release tablets (100 mg) were prepared using xanthan/guar gums and also hydroxypropyl methyl cellulose (HPMC) carboxymethyl-Cellulose (CMC) polymers by direct compression method. Physical characteristics of the tablets and water uptake in addition to their dissolution profiles were compared with standard (Lopressor SR) tablets. Dissolution test was performed in the phosphate buffer solution (pH 6.8) and the samples were analyzed spectrophotometerically in 275.7 nm. Dissolution studies showed that formulations containing 100 and 80% of HPMC, 100% of guar, and 20% of xanthan followed the Higuchi model, while those containing 60 and 40% HPMC and 100 and 80% xanthan followed a zero-order model. The tablets with 40% xanthen followed a Hixon-Crowell model. In cellulose derivatives the highest MDT and dissolution efficiency until 8 hr (DE8%) belonged to tablets with 40% HPMC, increasing the amount of CMC decreased the drug release rate, and formulations containing 60 and 40% of HPMC had the USP dissolution standards. While, in the gum formulations, the highest mean dissolution time and the lowest DE(8)% belonged to tablets with 100% xanthan, increasing the xanthan decreased the release rate of metoprolol, and formulations containing 80 and 100% xanthan had the USP dissolution standards. Results showed that natural gums are suitable for production of sustained-release tablets of metoprolol.