A sensitive LC-MS/MS method for the quantification of febuxostat in human plasma and its pharmacokinetic application

An improved, simple and highly sensitive LC-MS/MS method has been developed and validated for quantification of febuxostat with 100 L human plasma using febuxostat-d(7) as an internal standard (IS) according to regulatory guidelines. The analyte and IS were extracted from human plasma via liquid-liquid extraction using diethyl ether. The chromatographic separation was achieved on a Zorbax C-18 column using a mixture of acetonitrile and 5mm ammonium formate (60:40, v/v) as the mobile phase at a flow rate of 0.5mL/min. The total run time was 5.0min and the elution of febuxostat and IS occurred at 1.0 and 1.5min, respectively. A linear response function was established for the range of concentrations 1-6000ng/mL (r>0.99). The precursor to product ion transitions monitored for febuxostat and IS were m/z 317.1261.1 and 324.2262.1, respectively. The intra- and inter-day precisions (%RSD) were within 1.29-9.19 and 2.85-7.69%, respectively. The proposed method was successfully applied to pharmacokinetic studies in humans. Copyright (c) 2013 John Wiley & Sons, Ltd.