Pharmacokinetics and bioequivalence of two brands of metformin 500 mg tablets in Iranian healthy volunteers

The aim of this study was to evaluate the pharmacokinetics (PK) and bioequivalence (BE) of two metformin tablets. For in vitro evaluation, weight variation, assay and dissolution tests were performed. A randomized, single dose, two-period, cross over study in healthy male fasting volunteers was designed. A 2-week washout period separated the two periods. For analysis of PK parameters blood sampling was performed before and after drug administration in various time points up to 12 h. Metformin concentration in plasma was determined using a developed high performance liquid chromatography method. Both formulations passed the assay, content uniformity, and dissolution tests acceptance value. PK parameters, representing the rate and the extent of metformin absorption were calculated and analyzed for two formulations. The 90 % CI obtained by analysis of variance for the ratios of Cmax, AUC0-t, and AUC0-∞ were 92.14-110.95, 92.72-107.37 and 89.42-110.23 % respectively, meeting the criteria for BE (80-125 %). Administration of a single dose of test and reference formulations did not result in statistically significant differences between in vitro and in vivo BE parameters in healthy Iranian male volunteers. Thus in the case of rate and extent of absorption the test and reference formulations were considered bioequivalent. © 2013 The Korean Society of Pharmaceutical Sciences and Technology.