Abstract: A simple, sensitive, accurate and rapid HPLC method for naftopidil determination in dog plasma or serum has been developed. Naftopidil was extracted from alkalinized plasma or serum with diethyl ether. The mobile phase consists acetonitrile and 0.05 mol·L^-1 phosphate buffer (pH 6.5) (60:40). Verapamil was used as the internal standard and the eluate was monitored at 230 nm. The calibration curve of naftopidil was linear within the range of 10 ng·mL^-1(1200 ng·mL^-1. The recovery of this method is 100.23%±3.00%, within-day RSD and between-day RSD were no more than 3.30%, 5.56% respectively. The plasma drug concentration-time course in dogs after an oral single dose of 200 mg conformed to the one-compartment model. Mean T1/2Ke, Tmax, Cmax value were 3.19±1.27 h, 1.15±0.49 h, and 697.48±94.22 ng·mL^-1 respectively.

Key words: Naftopidil, Naftopidil, HPLC, HPLC, Pharmacokinetics, Pharmacokinetics