Formulation and Evaluation of Gastro-bilayer Floating Tablets of Simvastatin as Immediate Release Layer and Atenolol as Sustained Release Layer

Combination therapy is highly desired to deliver atenolol and simvastatin for dyslipidemia and hypertension as a concomitant drug treatment. On other hand, atenolol has poor absorption in lower gastrointestinal tract, short half-life and simvastatin has poor solubility. Therefore, the present study was to develop gastro-bilayer floating matrix tablet in which simvastatin was incorporated as immediate layer and atenolol as sustained release layer. Gastro-bilayer floating tablets were prepared by direct compression method and optimized using hydroxypropyl methylcellulose K100 (37.5% w/w) as release retardant and sodium bicarbonate as a gas-forming agent. The immediate release layer comprised sodium starch glycolate as superdisintegrant. The tablets of optimized formulations floated on the test medium for more than 12 h with 9 min of floating lag time. Atenolol release was sustained for 12 h via diffusion mechanism and more than 96% release of simvastatin within 15 min was achieved. It can be concluded that, the biphasic drug release pattern was successfully achieved through the formulation of gastro-floating bilayer tablets in this study, allowing strengthened combination therapy for hypertension and dyslipidemia.