Bioequivalent study of nifedipine sustained-release tablets in healthy volunteers

AIM To develop a LC-MS method for determining the nifedipine in human plasma.The pharmacoki- neties and bioequivalence of nifedipine sustained-release tablets were studied.METHODS The human plasma samples were obtained at certain time points after a single or multiple oral dose of the test or reference formulations.Plasma sam- pies were processed by liquid-liquid extraction using diazepam as the internal standard.The pharmacokinetic parameters were calculated and the bioequivalence of nifedipine sustained-release tablets were evaluated.RESULTS The main pharmacokinetic parameters of nifedipine test and reference formulations after a single oral administration were as follows: t_(max)=(2.2±0.7) and (2.3±0.8)h;ρ_(max)(68.3±23.2)and(71.1±18.6)μg·L~(-1);t_(1/2)(6.0±2.1) and (6.2±3.4) h.The relative bioavailability of nifedipine sustained-release tablets was (97.5±15.6) %.The main pharmacokinetic parameters after a multiple oral administration were as follows:t_(max)(2.0±0.8) and (2.2±0.9) h;ρ_(max)(63.1±26.8) and (63.5±24.7)μg·L~(-1);t_(1/2)(7.1±2.6) and (7.2±2.6) h.The relative bioavailability of nifedipine sustained-re- lease tablets was (97.1±30.5)%.CONCLUSION The developed LC-MS method is reliable,rapid and simple.The statistical analysis results show that the two formulations are bioequivalent.