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BACKGROUND Metformin hydrochloride (MH) is an oral anti-hyperglycemic agent belonging to the biguanide class of drugs. OBJECTIVE The present study involves the formulation and evaluation of gastro-retentive floating microparticles containing MH as a model drug for the prolongation of absorption time. METHODS Three levels of a three-factor, Box-Behnken design were used to evaluate the critical formulation variables. Microparticles were prepared using a water-in-oil-in-water double-emulsion solvent evaporation method and examined in terms of production yield, particle size, entrapment efficiency, floating ability, morphology, FTIR (Fourier transform infrared spectroscopy), and in vitro drug release. RESULTS The optimum conditions for preparing MH microparticles were predicted to be the content of ethyl cellulose content (150 mg), poly (ε-caprolactone) (150 mg), and polyvinyl alcohol (1 %w/v). The optimized MH microparticles were found to be spherical with a mean size of 350.2 µm. Entrapment efficiency was 58.62% for microparticles. 63.94% of microparticles showed floating properties. The FTIR analysis confirmed no chemical linkage between microparticle components. In vitro release study showed a controlled release for up to 8h. CONCLUSION These results demonstrated that MH microparticles, as a drug delivery system, may be useful to achieve a controlled drug release profile suitable for oral administration and may help to reduce the dose of drug and to improve patient compliance.