A validated UHPLC-MS/MS method for simultaneous determination of lumiracoxib and its hydroxylation and acyl glucuronidation metabolites in rat plasma: Application to a pharmacokinetic study.

Lumiracoxib is a selective cyclooxygenase-2 (COX-2) inhibitor. The aim of this study was to develop a simple and sensitive ultra-high performance liquid chromatography tandem mass spectrometric method (UHPLC-MS/MS) for the simultaneous determination of lumiracoxib and its circulating metabolites 4'-Hydroxyl-lumiracoxib and lumiracoxib-acyl-glucuronide in rat plasma. The analytes and diclofenac (internal standard, IS) were extracted using acetonitrile containing 0.2 % formic acid. Chromatographic separation was executed on ACQUITY BEH C column (2.1 × 50 mm, 1.7 μm) with water containing 0.2 % formic acid and acetonitrile as mobile phase. Mass detection was achieved in positive multiple reactions monitoring (MRM) mode, with precursor-to-product transitions at m/z 294.1 > 248.1, m/z 310.1 > 264.1, m/z 470.1 > 276.1 and m/z 296.0 > 250.0 for lumiracoxib, 4'-hydroxyl-lumiracoxib, lumiracoxib-acyl-glucuronide and for IS, respectively. The developed LC-MS/MS method was validated based on the guidance of U.S. Food and Drug Administration. The linearity was evident (r > 0.995) over the concentration ranges of 1-1000 ng/mL for lumiracoxib, 1-500 ng/mL for 4'-hydroxyl-lumiracoxib and 1-200 ng/mL for lumiracoxib-acyl-glucuronide, respectively. The precision (RSD) did not exceed 8.23 % and accuracy (RE) ranged from -7.85 % to 9.50 %. The extraction recovery was more than 80.54 %. All the analytes were demonstrated to be stable under the tested storage and processing conditions. The validated LC-MS/MS method has been successfully applied to the pharmacokinetic study of lumiracoxib and its metabolites in the rats after orally administered with lumiracoxib.