Imrecoxib is a specific inhibitor of cyclooxygenase-2. Its hydroxymethyl (M1) and carboxylic acid (M2) metabolites are the major circulating components in human plasma. It has been demonstrated that the anti-inflammatory activities of M1 and M2 are both equal to the parent drug. In the current study, a highly sensitive and rapid method was established and validated for the determination of imrecoxib, M1 and M2 in human plasma via liquid chromatography-tandem mass spectrometry technique. To our knowledge, this is the first study that simultaneously analyzed imrecoxib and its two active metabolites following a rapid protein-precipitation clean-up. Imrecoxib and its metabolites were separated on a reversed-C18 column (3.5 μm; 100 × 4.6 mm), and the mobile phase was optimized as 5 mM ammonium acetate: acetonitrile: formic acid (35: 65: 0.1, v/v/v), based on the pKa values of analytes. Mass spectrometric detection was conducted in a positive multiple reaction monitoring mode. The m/z transitions of imrecoxib (370.2 → 278.2), M1 (386.2 → 278.2) and M2 (400.2 → 236.2) were selected for an effective balance between sensitivity and selectivity. An excellent linearity was demonstrated over the concentration ranges of 0.100-40.0, 0.200-80.0 and 2.00-800 ng/mL for imrecoxib, M1 and M2, respectively. The method validation was carried out in agreement with the FDA guidance. Furthermore, the pharmacokinetic properties of imrecoxib and its two active metabolites were characterized in patients with moderate hepatic impairment, by using the developed and validated method.
Keywords: Human; Imrecoxib; Imrecoxib active metabolites; LC-MS/MS; Moderate impairment; Pharmacokinetics.
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