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

This study was conducted to compare the bioavailability of two controlled-r elease metformin preparations (Diabetmin Retard and Glucophage Retard) and also to correlate the in vitro and in vivo data obtained with the two prepa rations. Twelve healthy volunteers participated in the study, conducted acc ording to a completely randomized, two-way crossover design. The preparatio ns 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 rele ase and in vivo absorption. Diabetmin Retard demonstrated a slower rate of in vitro release, but a faster rate of in vivo absorption than Glucophage R etard. However, the in vivo absorption of both products was found to be slo wer 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 r ank 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 be tween the T-max values, but it may not be therapeutical significant. Moreov er, the 90% confidence interval for the ratio of the logarithmic transforme d AUC(0-infinity) values, as wc ll as the logarithmic transformed C-max val ues, of Diabetmin Retard over those of Glucophage Retard was within the acc eptance criteria of 0.80-1.25.