Development of a simple LC-MS/MS method for the determination of febuxostat in human plasma and its application to a bioequivalence study.

The purpose of this study was to design a simple, sensitive and rapid liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for a febuxostat bioequivalence study in healthy Chinese male volunteers. In this method, febuxostat and etodolac (internal standard) were isolated from plasma samples by protein precipitation with acetonitrile. The supernatant was chromatographed on a Zorbax SB-C18 (150 x 3.0 mm, 3.5-microm particle size, Agilent) column with a SecurityGuard Inertsil Symmetry C18 column (12.5 x 4.6 mm, 5-microm particle size, Waters). The lower limit of quantification for febuxostat in 0.2 mL of human plasma was 13.40 ng x mL(-1), and the linearity was achieved over a concentration range from 13.40 to 21440 ng x mL(-1). Febuxostat tablets from Hengrui Medicine Co., Ltd (test, Jiangsu, China) and from Takeda pharmaceuticals america, Inc. (reference, Deerfield, IL) were evaluated following a single 80 mg oral dose to 18 healthy volunteers. Bioequivalence was determined by calculating 90% confidence intervals (90% CI) for the ratio of C(max), AUC(0-t), and AUC(0-infinity) values for the test and reference products, using logarithmic transformed data. The calculated 90% CIs for the ratio of C(max) (88.7-131.2%), AUC(0-t) (99.2-122.7%) and AUC(0-infinity) (99.5-123.1%) values for the test and reference products were all located within the bioequivalence criteria range (80-125% for AUC, and 70-143% for Ca(mzax)), proposed by State of Food and Drug Administration [SFDA, 2005. China]. It was concluded that the two febuxostat formulations (test and reference) analyzed were bioequivalent in terms of rate and extent of absorption and the method met the principle of quick and easy clinical analysis.