A simple and sensitive high-performance liquid chromatography mass spectrometry（LC-MS）method for the simultaneous determination of irbesartan and hydrochlorothiazide in human plasma was developed and applied to a pharmacokinetic study. Acetaminophen was used as the internal standard（IS）.Sample pretreatment using liquid-liquid extraction with ethyl acetate was used.The analysis was carried out on an Elite SinoChrom ODS-BP C_（18）column with a mobile phase composed of acetonitrile-water （35：65,v/v）.Target ions were [M-H]^-m/z 427.25 for irbesartan,[M-H]^-m/z 295.95 for hydrochlorothiazide and [M-H]^- m/z 150.05 for the IS via an electrospray ionization（ESI）source.The intra-and inter-day precision（RSD%）was below 14.5% for irbesartan and hydrochlorothiazide,and the accuracy（RE%）was less than 1.9% and-2.0% for irbesartan and hydrochlorothiazide,respectively.The linear calibration curves were obtained in the concentration range of 10-5000 ng/mL （r0.99）for irbesartan and 1-200 ng/mL（r0.99）for hydrochlorothiazide with the lower limit of quantification（LLOQ）of 10 ng/mL and 1 ng/mL,respectively.The method was applied to a clinical pharmacokinetic study of a tablet containing irbesartan and hydrochlorothiazide in healthy Chinese volunteers after oral administration.
