Identification of etamiphylline and metabolites in equine plasma and urine by accurate mass and liquid chromatography/tandem mass spectrometry

Abstract

Etamiphylline camsylate (Millophylline V) was administered intravenously to two horses at a dose of 2.8 mg/kg. Urine and blood samples were taken up to 32 h post administration. Unhydrolyzed plasma and urine was extracted using solid phase extraction (SPE). The identity of the parent drug and metabolites was confirmed using a linear ion trap mass spectrometer and accurate mass analysis on an orbitrap mass spectrometer. Desethyletamiphylline (molecular weight 251) was the main metabolite observed in the urine and plasma samples and resulted from the N-deethylation of etamiphylline. The second metabolite detected in urine and plasma resulted from the demethylation of etamiphylline (molecular weight 265). The third minor metabolite detected in urine was proposed to have resulted from a simultaneous N-deethylation and demethylation of etamiphylline (molecular weight 238).

Clinical Applications

“…Further, retrospective interrogation of full-scan data can be useful to investigate the presence of new compounds/metabolites (such as new 'designer drugs') without re-analysis. Newer Orbitrap ® /Exactive™ technology (ThermoFisher Scientific), also capable of HRMS, is finding toxicologically relevant applications [171][172][173] . "In house" library matching should be carried out for unequivocal compound identification because mass spectral libraries and compound databases may not be completely transferable between instruments.…”

LC‐MS in analytical toxicology: some practical considerations

“…Further, retrospective interrogation of full‐scan data can be useful to investigate the presence of new compounds/metabolites (such as new ‘designer drugs’) without re‐analysis (Peters et al ., 2010). Newer Orbitrap®/Exactive™ technology (ThermoFisher Scientific), also capable of HRMS, is finding some toxicologically relevant applications (Thomas et al ., 2010b; Weider et al ., 2010; Johnson and Kozak, 2010) and may be a useful tool for the future.…”