Identification of a benzhydrolic metabolite of ketoprofen in horses by gas chromatography-mass spectrometry and high-performance liquid chromatography.

A benzhydrolic metabolite of ketoprofen, formed by reduction of the keto group of the drug, has been identified by gas chromatography—mass spectrometry in equine plasma and urine. After partial synthesis, its structure has been confirmed by UV, IR and 1H NMR spectroscopy. The kinetics of ketoprofen and this metabolite have been monitored in plasma by high-performance liquid chromatography. The two products were quantified in plasma up to 4 and 3 h, respectively, and were detected in urine up to 72 and 24 h, respectively, after a single intravenous administration to horses at the dose of 2.2 mg/kg. Simultaneous detection of both compounds increases the reliability of antidoping control analysis.