Identification of metoclopramide metabolites in the urine of cattle by gas chromatography-mass spectrometry and high-performance liquid chromatography-photodiode array detection

The urinary metabolites of metoclopramide (4-amino-5-chloro-N-2-diethylaminoethyl]-2-methoxybenzamide) were identified in cows. The drug was administered intravenously, voided urine was collected, and individual urine extracts were analysed by gas chromatography-mass spectrometry and high-performance liquid chromatography-photodiode array detection. The parent compound and one major metabolite (4-amino-5-chloro-N-2-(ethylamino)ethyl]-2-methoxybenzamide) were common to all individuals. In addition to the parent and major metabolite, a second, minor metabolite was identified in two cows as 4-amino-5-chloro-N-2-(diethylamino)ethyl]-2-hydroxybenzamide. The identity of the minor metabolite was confirmed by comparison with a standard synthesized by a new method. Metabolite identification and characterization in food animal species allows the design of safety and environmental impact studies and relative metabolite ratios between dose treatment groups.Abbreviations ¹H-NMR proton nuclear magnetic resonance - R _T retention time - D₁ dopamine-1 - D₂ dopamine-2 - 5-HT₃ 5-hydroxytryptamine - GC-MS gas chromatography-mass spectrometry - HPLC high-performance liquid chromatography - UV-vis ultraviolet-visible - ID internal diameter - m/z mass/charge ratio