METABOLISM OF [4-14C]NORETHISTERONE IN WOMEN

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Abstract
SUMMARY: After the administration of norethisterone to seven human subjects 37·4% to 80·6% of the dose was excreted in the urine within 5 days. About half of the urinary radioactivity was extractable after acid or enzymatic hydrolysis and about 80% was extracted by using a serial hydrolytic and extraction procedure. About 15% of the urinary radioactivity was present as sulphate conjugates. About 5% of the urinary radioactivity was present in acidic or phenolic compounds. No metabolism of the ethynyl group seemed to occur and the Girard reaction showed that about half of the urinary metabolites were ketonic. The metabolites in the glucuronide fraction of urine were predominantly more polar on paper chromatography than tetrahydronorethisterone, whereas in the sulphate fraction most of the metabolites had a polarity similar to the simple reduction products of norethisterone. Two days after injection the plasma still contained about 5% of the administered dose.