Metformin hydrochloride is an biguanide class of antidiabetic agent superior to the phenformin, therefore an attempt to extend release of metformin hydrochloride was carried out using Eudragit L100, Eudragit NE 30D and Hydroxy propyl methyl cellulose (HPMC)/ethylcellulose (EC) combination. The technique employed was wet granulation followed by compression. The matrix tablets prepared with different proportions of the retarding polymers were subjected to various physico-chemical characterizations. The in vitro release profiles of the resulting tablets were evaluated in 0.1N Hcl for 2 hrs and pH 6.8 phosphate buffer for remaining hours. Preliminary data suggested that the matrix tablets made with HPMC/EC combination of polymer showed a great promise as a retardant for release. The other in process quality parameters were also studied for the same batch of tablets that gave in vitro profiles in accordance with the theoretical release profiles. The shelf life of the product was determined by subjecting the tablets to various temperatures. The stability of drug in the formulation was determined using Fourier transform infrared spectroscopy. The release kinetics has been examined for the tablets with respect to the in vitro profiles and stability data from the stand point of a diffusion controlled process (Higuchi profile) and that of a first order kinetics. Bioavailability study using rabbits was also performed for the matrix tablets (HPMC/EC) and the pharmacokinetic treatment was given to the in vivo data obtained. The in vitro and the in vivo studies revealed the potential suitability of HPMC/ EC polymers to formulate the matrix tablets for sustaining the release of metformin hydrochloride.
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