Rotating in vitro in vivo data of two controlled-release metformin formulations

This study was conducted to compare the bioavailability of two controlled-release metformin preparations (Diabetmin Retard and Glucophage Retard) and also to correlate the in vitro and in vivo data obtained with the two preparations. Twelve healthy volunteers participated in the study, conducted according to a completely randomized, two-way crossover design. The preparations were compared using area under the plasma concentration-time curve AUC(0-infinity), time to reach peak plasma concentration T-max, and peak plasma concentration C-max, while correlation was determined between in vitro release and in vivo absorption. Diabetmin Retard demonstrated a slower rate of in vitro release, but a faster rate of in vivo absorption than Glucophage Retard. However, the in vivo absorption of both products was found to be slower than that of drug released in vitro. A satisfactory relationship could be established between the in vitro and in vivo results, but there was no rank order correlation. No statistically significant difference was observed between the two preparations in the parameters AUC(0-infinity), and C-max. However, a slight but statistically significant difference was observed between the T-max values, but it may not be therapeutical significant. Moreover, the 90% confidence interval for the ratio of the logarithmic transformed AUC(0-infinity) values, as wc ll as the logarithmic transformed C-max values, of Diabetmin Retard over those of Glucophage Retard was within the acceptance criteria of 0.80-1.25.