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 DE8% 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.