Formulation and Characterization of Sustained Release Floating Microballoons of Metformin Hydrochloride

Purpose: To formulate sustained release gastroretentive microballoons of metformin hydrochloride with the objective of improving its bioavailability. Methods: Microballoons of metformin hydrochloride were formulated by solvent evaporation and diffusion method using varying mixtures of hydroxypropyl methylcellulose (HPMC) and ethyl cellulose (EC) polymers. The balloons were characterized for particle size, surface morphology, incorporation efficiency, floating behavior and in vitro drug release. Results: The mean particle size of the formulated microballoons was in the range of 34.2 +/- 4.7 to 95.7 +/- 2.2 mu m. Incorporation efficiencies of over 83.8 +/- 0.9 % were achieved for the optimized formulations. Most of the formulations were buoyant with maximum buoyancy of 81.4 +/- 2.0 % for > 12 h, showing good floating behavior of microballoons. Release kinetic data showed best fit to the Higuchi model, indicating that diffusion was the predominant mechanism of drug release. Conclusion: Microballoons is a potential suitable delivery system for sustained release of metformin hydrochloride with improved bioavailability when compared with conventional dosage forms of the drug.