The metabolism of metoclopramide 1 has been re investigated by HPLC coupled with mass spectrometry. The urine of healthy volunteers showed the presence of a new metabolite 2 derived from the enzymatic oxidation of the primary aromatic amino group of 1 to the hydroxylamino moiety. The structure of the new metabolite was ascertained by its fragmentation pattern in the mass spectrometer and unambiguously secured by an ...