Pharmacokinetics of nifedipine in Taiwanese

To elucidate the pharmacokinetics of nifedipine in Taiwanese, a retrospective review of nifedipine bioequivalence studies completed in Taiwan in the past 5 years was conducted. A total of 198 healthy male volunteers were given a single dose of a 10 mg Adalat(R) capsule as a reference drug after overnight fasting. Pharmacokinetic parameters derived from Adalat(R) administration were calculated by non-compartmental analysis with the WinNonlin program. After oral administration of an immediate-release dosage form of a 10 mg nifedipine capsule to Taiwan residents, a skewed distribution with no clear evidence of bimodality of pharmacokinetic parameters was observed. The mean C-max was 143.12 +/- 53.48 ng/ml, the mean AUC was 293.77 +/- 115.62 ng (.) h/ml, the mean T-1/2 was 3.08 +/- 1.61 h, and the median value of T-max was 0.61 h. Compared with other published studies, the C-max and AUC of nifedipine after 10 mg administration were significantly higher in Taiwanese than in British and American subjects. However, the C-max and AUC were similar to those of Indian and Mexican subjects. According to the antimode of AUC distribution of 22.5 ng (.) h/ml/mg proposed by Kleinbloesem, 69.7% of Taiwanese can be categorized as slow metabolizers. Based on the results in this study, the majority of Taiwanese show lower activity of nifedipine metabolism. Copyright (C) 2004 John Wiley Sons, Ltd.