Formulation Optimization and Consistency Evaluation of In Vitro Release for Felodipine-metoprolol Sustained-release Tablets

OBJECTIVE To optimize the formulation of felodipine-metoprolol sustained-release tablets and evaluate the consistency of their release in vitro with commercially available preparations. METHODS The release of felodipine and metoprolol was analyzed by HPLC. The influences of crucial factors of solid dispersion, pellets, and tablets on the release of felodipine and metoprolol were investigated and thereby the formulation was optimized. RESULTS The components of pellets, particle size of pellets, amount of porogenic agent in pellet membrane, weight gain of pellets, and amount of retarding agent significantly influenced the in vitro release of felodipine or metoprolol. The release of felodipine and metoprolol from self-made felodipine-metoprolol sustained-release tablets in 0.3% SDS solution, pH 4.0 citrate buffer solution containing 0.3% SDS, pH 6.8 phosphate buffered saline containing 0.3% SDS, and 0.1 μmol·L^-1 HCl containing 0.3% SDS was conformed with that from commercial felodipine-metoprolol sustained-release tablets. CONCLUSION The self-made felodipine-metoprolol sustained-release tablets has the consistent release behaviour with the commercial ones.