[Bioequivalence of generic drugs and substitution: example of depot verapamil]

Following oral administration of 240 mg Verapamil-HCl as Isoptin RR, Veramex SR 240 and durasoptin SR 240, plasma concentration time curves of Verapamil and ECG changes were determined in 14 healthy subjects. There was a linear correlation between maximal plasma concentration and prolongation of PQ-intervals of the ECG. No hysteresis was observed when the changes in PQ-interval were plotted against plasma concentration. Comparison of concentration and effect profiles showed that the three formulations were not equivalent and a change in therapy from one to the other cannot be recommended.