Pharmacokinetic Study of Nifedipine in Healthy Adult Male Human Volunteers

Purpose: To evaluate the pharmacokinetics of nifedipine in healthy adult Pakistani subjects. Methods: Each of six fasting volunteers received 20 mg nifedipine (2 x Adalat® 10 mg capsules) orally once and then another one week later. Their blood samples were obtained at regular time intervals and analysed by HPLC. Using the non-compartmental approach, plasma levels of nifedipine were employed to compute their individual disposition kinetics, including Cmax (maximum plasma concentration), Tmax (time to reach maximum plasma concentration), MRT (mean residence time), AUC0-∞ (area under curve), AUMC0-∞ (area under first moment curve) and Ka (absorption rate constant). Results: The suggested therapeutic level of nifedipine for the treatment of hypertension (15-35 ng.mL-1) was achieved in all six volunteers within 0.25 h after dose administration, and maintained for more than 6 h. Tmax was 1.58 h and Cmax varied from 140 – 300 ng.mL-1. Mean absorption rate constant was 2.22 h-1 while mean absorption half-life was 0.43 h. The mean elimination rate constant was 0.16 h-1 while 5.7 h was recorded for terminal half-life. AUC0-∞, AUMC0-∞ and MRT were 1879.86 ng.h.mL-1, 8244.04 ng.h2.mL-1 and 4.2 h, respectively. Conclusion: This study confirms the rapid absorption of nifedipine in humans. AUC was similar to that previously reported for Nigerians but slightly lower than that stated in the literature for other south Asian races. Further studies on large segments of the local population using the non-compartmental model for kinetic analysis is recommended.