Metabolisme et distribution tissulaire de la dL ephedrine 14C

The excretion and metabolism of dl ephedrine-β-14C have been investigated in rats. After i.p. administration of ephedrine 14C (2 mg/kg), approximately 85 per cent of the radioactivity was eliminated in the first 40 hr, 80 per cent by urine and 5 per cent by feces. Analysis of urinary metabolites indicated two possible metabolic pathways. The major route (25 per cent of the urinary radioactivity) was ring parahydroxylation leading to paraphenolic compounds, parahydroxyephedrine or parahydroxynorephedrine (no distinction being made between these two products): 80 per cent or more of these compounds were excreted as glucuronide conjugates. The minor metabolic pathway (5 per cent) was oxidative deamination of the ephedrine side chain leading to acidic metabolites corresponding to the Rf value of hippuric and benzoic acid. 70 per cent of urinary radioactivity during the first 18 hr was ephedrine 14C but during the following period 18–40 hr, ephedrine paraphenolic derivatives accounted for more than 80 per cent of the urinary radioactivity. Tissue distribution of ephedrine 14C was studied at various times after i.v. injection (5 mg/kg) in the mouse by autoradiography and quantitatively in the rat: 15 min after ephedrine 14C administration, the relative tissue distribution of radioactivity was: kidney > lung, adrenal, spleen, liver > intestine. stomach > brain, heart > plasma. Adrenal uptake was specially important and localized in the medullary part of the gland. Loss of radioactivity in the interval 15–120 min varied from 10 to 50 per cent according to the organs. Ephedrine 14C was slowly metabolized and two hours after injection represented more than 80 per cent of radioactivity in the studied tissues except plasma, kidney and liver.