Bioinequivalence of marketed diltiazem preparations

A bioequivalence study of three brands of regular diltiazem--Angizem (A), Dilzem (B) and Herbesser (C) has been carried out in 5 healthy, male volunteers. After a single oral dose of 60 mg of each preparation, the mean AUC (0-8 h) and Cmax of preparation B was significantly higher than of brands A and C. The tmax of A and B was significantly lower than of C. B had a higher dissolution rate in vitro (98.8% dissolved in 45 min) than A and C. Thus, there was bioinequivalence of the three brands of diltiazem, due partly to differences in dissolution and perhaps in part to a first pass effect.