OBJECTIVE To develop a LC-MS/MS method for the determination of ezetimibe and total ezetimibe in human plasma and to study its pharmacokinetics in Chinese healthy volunteers.METHODS The analyte and internal standard(¹³C6-ezetimibe)were extracted from plasma samples by liquid-liquid extraction with methyl tert-butyl ether.The reversed-phase chromatographic separation was performed on a Capcell C₁₈ column(2 mm×50 mm,5 μm),and the extract was eluted with a gradient consisting of acetonitrile and 5 mmol·L^-1 ammonium acetate at a flow rate of 0.25 mL·min^-1.The analyte was detected using negative ionization by multiple reaction monitoring mode.The mass transition paires of m/z 408.5→ m/z 207.8 and m/z 408.5→ m/z 207.8 were applied to detect ezetimibe,and ¹³C6-ezetimibe was used to quantify ezetimibe and total ezetimibe.RESULTS A good linearity was obtained in the concentration range of 0.020～20μg·L^-1(r=0.999 4,n=9)for ezetimibe and 0.25～250 μg·L^-1(r=0.999 8,n=9)for total ezetimibe in human plasma.The inter-and intra-day precision(RSD)were less than 12% and the method recoverys were within 97%～104%.The pharmacokinetic parameters of ezetimibe and total ezetimibe after a single oral administration of 10 mg ezetimibe tablets were as follows:AUC_0-inf(121.9±41.7)and(536.8±182.7)μg·h·L^-1;AUC_0-t(102.1±31.4)and(478.8±170.0)μg·h·L^-1;ρ_max(4.9±1.6)and(48.5±17.3)μg·L^-1;t_max(5.2±6.4)and(1.5±0.9)h;t_1/2(26.4±28.8)and(22.5±11.0)h;MRT(23.6±3.8)and(19.7±3.8)h,respectively.CONCLUSION A reliable LC-MS/MS method is developed and validated for the determination of ezetimibe and total ezetimibe in human plasma.The parameters of its pharmacokinetics in Chinese male volunteers are same as reported abroad.