Development and In Vitro Evaluation of Modified Release Coated Tablets of Freely Water Soluble Drug Metoprolol Succinate

The purpose of the present study was to design, characterize and evaluate extended release coated tablets of Metoprolol Succinate (MS) to reduce its dosing frequency. Core tablets were prepared using various matrix forming agents like HPMC, HPC, and HEC, and further subjected for coating using blend of aqueous dispersion of a hydrophobic and hydrophilic polymer, (Surelease®: HPMC E15) to control the drug release of the highly water soluble drug Metoprolol Succinate. Varying the matrix forming agent concentrations in the core tablets and percentage coating build up on core tablets showed range of drug release patterns in phosphate buffer pH 6.8. The present study dealt with the suitable grade of cellulose polymer and optimized coating composition which can modify the drug release to match up with the USP dissolution specifications and marketed product for the MS. The optimized formulation containing Metolose 90 SH 100000 and 3% coating with plasticized Surelease: hydroxypropyl methylcellulose (HPMC E15) showed extended drug release up to 24hrs and the drug release pattern was similar with the specifications. The in-vitro dissolution studies revealed that the release rate is inversely proportional to the concentration of matrix former in the core tablet and percent of coating thickness. The kinetic treatment illustrate that the optimized formulation HMC5 followed zero order kinetics with diffusion mediated drug release which is evidenced from n value of (0.73) Peppas equation. FT-IR and DSC studies indicated no interaction between the drug and excipients and prepared formulations showed good stability as per ICH guidelines. Key words: Metoprolol Succinate, Extended Release, HPMC E15, Surelease, Coated Tablet