ABSTRACT

The aim was to design bilayer tablets of rosuvastatin and diltiazem hydrochloride to give conventional release of rosuvastatin calcium and sustained release of diltiazem hydrochloride. The conventional release layer comprised lactose and micro crystalline cellulose as diluents (separately and in combined form) and the sustained release layer comprised HPMC K100M and ethyl cellulose (with different ratio of HPMC K100M and ethyl cellulose) as the release retarding polymers. Direct compression method was used for formulation of the bilayer tablets. Preformu-lation studies were performed prior to compression. The bilayer tablets were evaluated for weight variation, di-mension, hardness, friability, drug content, and disintegration time and in vitro drug release using USP dissolution apparatus type II (paddle). More than 90% of rosuvastatin calcium was released within 150 min. HPMC K100M and Ethyl cellulose sustained the release of diltiazem hydrochloride from the sustained release layer for 24 hour. After stability tests, degradation of both drugs were found but the drugs contents were found within the range. The release of diltiazem hydrochloride was found to follow a mixed pattern of Korsmeyer-Peppas, Higuchi model and zero order release models and the kinetic studies of the formulations revealed that diffusion is the predominant mechanism of drug release. The IR spectrum studies revealed that there was no disturbance in the principal peaks of pure drugs. This further confirms the integrity of pure drugs and no incompatibility of them with excipients. The stability studies were carried out for the optimized batch for three months and it showed acceptable results.