EVALUATION AND OPTIMIZATION OF GAS‑GENERATING AGENTS IN FLOATING BILAYER TABLETS OF METFORMIN HYDROCHLORIDE AND CANAGLIFLOZIN

OBJECTIVE: The present study was designed to systematically evaluate and optimize gas generating agents for the development of a gastro retentive floating bilayer tablet containing metformin hydrochloride (sustained release layer) and canagliflozin (immediate release layer). METHODS: The investigation was carried out in two sequential stages. Initially, different gas generating agents sodium bicarbonate, sodium carbonate, potassium carbonate and calcium carbonate were screened at a fixed concentration of 7.5% w/w of the sustained release (SR) layer (batches C7–C10). Based on performance, sodium bicarbonate was selected for further optimization at varying concentrations of 5%, 7.5% and 10% w/w (batches C11, C7 and C12). Bilayer tablets were prepared using direct compression technique. Floating characteristics were assessed in simulated gastric fluid, while drug content and dissolution studies were performed using validated analytical methods. RESULTS: Among the tested agents, sodium bicarbonate demonstrated superior buoyancy characteristics. A concentration dependent reduction in floating lag time was observed. Batch C12, containing 10% w/w sodium bicarbonate (80 mg per 800 mg SR layer), exhibited the shortest floating lag time (65 ± 3 s) and remained buoyant for more than 12 h. The formulation also showed sustained release of metformin over 12 h and rapid release of canagliflozin within 30 min. All evaluated parameters complied with pharmacopeial specifications. CONCLUSION: Sodium bicarbonate at 10% w/w was identified as the optimal gas generating agent concentration for achieving rapid onset of buoyancy and prolonged gastric retention in the developed bilayer tablet system.