Abstract: AIM: To investigate the pharmacokinetic properties and bioequivalence of nifedipine sustained-release tablets after multiple doses administration in healthy volunteers.METHODS: Twenty two male healthy volunteers were enrolled in a randomized two-way crossover design with multiple doses (20 mg·d^-1 ×;7 d)study.Nitrendipine was used as the internal standard and the concentrations of nifedipine in plasma were determined by HPLC-APCI-MS.The pharmacokinetic parameters were calculated and the bioequivalence were compared by DAS(ver 1.0)program.RESULTS: The pharmacokinetic parameters of test and reference preparations were as follows:C_max(52.5 ±;27.4)and (54.0 ±;31.2)ng·ml^-1;C_min(5.4 ±;4.1)and (6.2 ±;5.9)ng·ml^-1;C_av(16.8±;9.2)and (19.3 ±;12.4)ng·ml^-1;T_max(3.7 ±;0.9)and (4.1 ±;1.1)h;t_{1 2}(8.9 ±;4.9)and (8.5 ±;3.1)h;AUC_{0 -τ}(403.4 ±;221.0)and (461.9 ±;296.6)μg·h·L^-1 , AUC_0-36h (444.4 ±;256.1)and (503.1 ±;330.9) ng·h·ml^-1;AUC_{0 -∞} (482.1 ±;268.9) and(542.3 ±;348.4)ng·h·ml^-1;DF (299.8 ±;117.7)%and (279.2 ±;97.5)%, respectively.There were no significantdifferences (P>;0.05)in T_max , C_max , C_min ,Cav , DF , AUC_{0 -τ} , AUC_{0 -36}h , AUC_{0 -∞} and t_{1 2} between the two preparations.The relative bioavailability of test tablets was (100.6 ±;38.6)%.CONCLUSION: The test and reference preparations were bioequivalence.

Key words: nifedipine, pharmacokinetics, bioequivalence, bioavailability, HPLC-APCI-MS