The metabolic disposition of [14C]pivhydrazine, [14C]mebanazine, and [14C]benzylhydrazine in the rat.

The hydrazine drugs, [14C]pivhydrazine and [14C]mebanazine and the related compound [14C]benzylhydrazine were readily absorbed from the rat gut and the radioactivity was excreted mainly in urine. The major urinary metabolite of pivhydrazine and benzylhydrazine was [14C]hippuric acid, whereas mebanazine was shown to be excreted largely unchanged. Biliary excretion (21 and 24%, respectively) of radioactive material was observed after administration of [14C]pivhydrazine and [14C]mebanazine to bile duct-cannulated rats but only small amounts (approximately 3%) were excreted in bile after [14C]benzylhydrazine administration. The major biliary metabolites of pivhydrazine and mebanazine are acid-labile conjugates, possibly N-glucuronides. In vitro studies with rat liver homogenate suggest that benzylhyrazine may be an intermediate in the metabolism of pivhydrazine. The distribution of radioactivity in the rat 7 days after the administration of [14C]pivhydrazine and [14C]pivhydrazine and [14C]mebanazine is described.