Development and evaluation of regioselective bilayer floating tablets of Atenolol and Lovastatin for biphasic release profile

This study was performed to design bilayer regioselective floating tablets of atenolol and lovastatin to give immediate release of lovastatin and sustained release of atenolol. Bilayer floating tablets comprised two layers, i.e immediate release and controlled release layers. The immediate release layer comprised sodium starch glycollate as a super disintegrant and the sustained release layer comprised HPMC K100M and xanthan gum as the release retarding polymers. Sodium bicarbonate was used as a gas generating agent. Direct compression method was used for formulation of the bilayer tablets. Accelerated stability studies were carried out on the prepared tablets inaccordance with ICH guidelines. Roentgenography was carried out to study the in vivo buoyancy of the optimized formulation. All formulations floated for more than 12 h. More than 90% of lovastatin was released within 30 min. HPMC K100M and xanthan gum sustained retarded the release of atenolol from the controlled release layer for 12 h. After stability tests, degradation of both drugs were found but the drugs, contents were found to be within the range. Diffusion exponents (n) were determined for all the formulations (0.53-0.59). The release of atenolol was found to follow a mixed pattern of Korsmeyer-Peppas, Hixson-Crowell and zero order release models. The optimized formulation was found to be buoyant for 8 h in stomach. Therefore, biphasic drug release pattern was successfully achieved through the formulation of floating bilayer tablets inthis study.