Abstract: AIM: To study the pharmacokinetics and relative bioavailability of naftopidil in healthy male volunteers .METHODS: The naftopidil concentrations in plasma were determined by HPLC.The test and reference formulations of naftopidil were given to 18 healthy male volunteers .The calibration curve was linearwithin the range of 1.6-400 μg·L^-1, r =1.The minimum detection limit was 1 μg·L^-1.The mean recovery rate was 85.2 % -89.9 %, RSDs of inter-day and intra-day were no more than 8.0 %.RESULTS: After a single oral dose of 50 mg naftopidil test capsules or reference tablets, the main pharmacokinetic parameters AUC_0-24:295.6±90.9 and 291.6±89.3 μg·L^-1 ·h-1 ;AUC_0-∞:320.0±97.2 and 318.0±98.3 μg·L^-1·h^-1 ;T_max:0.6±0.2 and 0.6±0.2 h ;C_max:129.1±60.7 and 138.3±72.5μg·L^-1 ;T1 2:5.9±1.7 and 6.4±2.1 h, respectively.The relative bioavailability F_0-24, F_0-∞ were 101.9±12.9 % and 101.2±12.3 %, respectively.CONCLUSION: No significant difference exists among the pharmacokinetic parameters for the test capsules and the reference tablets of naftopidil.The two formulations were bioequivalent.

Key words: naftopidil, HPLC, pharmacokinetics, bioequivalence