IDENTIFICATION AND FULL CHARACTERIZATION OF A NEW METABOLITE OF METOCLOPRAMIDE

The metabolism of metoclopramide 1 has been reinvestigated 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 independent synthesis. In addition, the tertiary amine group of 1 was selectively oxidized to the corresponding N-oxide. This compound and its ring oxidation metabolites were not detected in the urine of the tested volunteers.