Formulation Development of Metoprolol Succinate Controlled Release Tablets using Ethyl-cellulose-polyvinyl-pyrrolidone Coating

It is challenging to develop a controlled release (CR) formulation for a freely water soluble drug molecule without using rate controlling polymers in the core matrix. This study is aimed to develop and evaluate cost-effective ethyl cellulose (EC)-polyvinyl pyrrolidone (PVP) film coating that can effectively control the release of freely water soluble drug, metoprolol succinate (MS) and to match that of release profile with its marketed tablet. Simple core tables of MS were compressed and coated with a solution composed of hydrophobic rate controlling polymer, EC and water soluble pore forming polymer, PVP. The effect of formulation parameters such as the ratio of EC to PVP and tablet coating weight gain on the in-vitro drug release were evaluated. Release profile of the optimized formulation at different pH conditions was determined and the similarity factor (f2) with marketed release profile was calculated.It was observed that drug release rate increased with a decrease in the ratio of ethyl cellulose to PVP and decreased with increased weight gain of the coating membrane. Among all the formulations, the formulation with EC and PVP at a ratio of 60:40 %w/w and 9% weight gain showed matching release profile to marketed tablet with f2 value of 72.25. The optimized formulation showed pH independent in-vitro release. This study successfully demonstrated that EC-PVP film coating can effectively control the release rate of freely soluble drugs. Once a day CR formulation of metoprolol succinate pharmaceutically equivalent to marketed tablet was developed.