Abstract: AIM: To establish a reversed phase highperformance liquid chromatographic method to determine cilostazol in human plasma and to study the pharmacokinetics of cilostazol in 10 healthy volunteers. METHODS: Using diazepam as the internal standard, cilostazol was extracted from human plasma with a mixture of 2mol ·L^-1 NaOH-diethyl ether anhydrous (1:4).The mobile phase was acetonitrile-water (45:55), flow rate 1 ml· min^-1, and the UV absorbance wavelength 254 nm.The pharmacokinetic analysis of cilostazol in 10 healthy volunteers after oral administration of 100mg was studied. RESULTS: Linear range of the standard curve was from 20 to 2 000 μg·L^-1 (r=0.9999).The quantitative limit for cilostazol was 10 μg·L^-1.The mean extraction recovery was 80.2 %±3.6 %.The mean analytical recovery was 97.0 % ±3.8 %.The relative standard deviation of intra-day and inter-day did not exceed 5.8 % and 10.1 %, respectively.It was found to be fitted to a twocompartment open model and its pharmacokinetic parameters were as follow:t_max 3.58 ±1.08 h, C_max 920 ±230 μg ·L^-1 AUC_0-48 11.0 ±3.3 mg·h^-1 ·L^-1, respectively. CONCLUSION: The method is suitable for drug monitoring of cilostazol and the pharmacokinetics of cilostazol in human provides a useful index for clinical trial.

Key words: cilostazol, high-performance liquid chromatography, serum concentration, pharmacokinetics