Comparative pharmacokinetics of two nifedipine products in capsule form following single oral administration in healthy volunteers.

The pharmacokinetic parameters (AUC, Cmax, Tmax, and t1/2) of nifedipine following single oral administration of a 10 mg capsule of test product were compared to those of the same amount of a reference product. The two products in capsule form were administered according to a randomized two-way crossover design in 22 healthy male volunteers. Nifedipine plasma concentrations were determined using a rapid, sensitive and precise high performance liquid chromatography (HPLC) method with ultraviolet (UV) detection at 235 nm. The parametric 90% confidence intervals of the mean value of the ratio [Myogard (test product) /Adalat (reference product)] for pharmacokinetic parameters were 0.90-1.08, 0.80-1.07, and 0.93-1.12 for AUC0-->infinity, Cmax and t1/2, respectively. In each case, values were within the acceptable bioequivalence range of 0.8-1.25. Distribution free point estimate for the difference in expected medians of Tmax of the two products (Myogard-Adalat) was 0.00 h with a 90% confidence interval of 0.00-0.13 which is greater than the accepted bioequivalence of +/- 0.12. The kinetic parameters were comparable to those reported for nifedipine, and no statistically significant differences were found in any of them when comparing the two products by analysis of variance (ANOVA) on log-transformed data. Thus, the two products could be considered bioequivalent regarding absorption rate (Cmax and Tmax), extent of absorption (Cmax and AUC) and elimination (t1/2).