The metabolism of [14C]N-ethoxycarbonyl-3-morpholinosydnonimine (molsidomine) in laboratory animals.

[14C]N-Ethoxycarbonyl-3-morpholinosydnonimine (molsidomine, Corvaton) was found to be extensively metabolized following oral dosing to rat and dog and intravenous dosing to rabbit. The majority of the radiolabel was rapidly excreted in the urine with the main radiolabelled components being characterized as acidic metabolites resulting from oxidative metabolism of the morpholine ring. A new metabolite, (N-cyanomethylenamino-2-aminoethoxy)-acetic acid, was identified and shown to be a major component of the 14C-labelled urinary metabolites in all three species. However, the previously identified metabolite, N-cyanomethylenaminomorpholine-2-one (compound D) was not detected and may therefore have been formed artefactually in the earlier studies. The long terminal half-life for plasma radioactivity observed in previous studies was shown to be the result of the production of small amounts of 14C-thiocyanate from the nitrile-containing metabolites of molsidomine.