Relative bioavailability study of two nifedipine tablet formulations in healthy male volunteers

OBJECTIVE: To assess the bioequivalence of two oral formulations containing 10 mg of nifedipine. The test preparation were Macorel tablets, the reference preparation were Adalat tablets. SUBJECTS, MATERIAL AND METHODS: The study was designed as a single-dose, three-period crossover randomized design to 18 non-smoker, healthy male volunteers under fasting conditions. Seventeen volunteers completed the study. Plasma samples were analyzed for nifedipine by HPLC after solid-phase extraction. The pharmacokinetic parameters used to assess the bioequivalence of the two formulations were AUC(0-infinite) and AUC(0-t) for the extent of absorption and Cmax and Tmax for the rate of absorption. Statistical comparisons of AUC(0-infinite) AUC(0-t), and Cmax data were evaluated after logarithmic transformation by two-way analysis of variance (ANOVA), and differences of Tmax were tested non-parametricaly. RESULTS: Point estimates (90% confidence intervals) of the test/reference ratios were 97.4% (87.6%-108.3%) for AUC(0-infinite) 97.0% (85.6%-110.1%) for AUC0-t, and 107.7% (89.1%-130.7%) for Cmax. No statistically significant difference was found for Tmax and elimination half-life values. CONCLUSION: Therefore, in accordance with the European Union bioequivalence requirements, the test and reference nifedipine preparations are bioequivalent for both the extent and the rate of absorption.