METABOLISM OF [4-14C]LYNESTRENOL IN MAN

Abstract

SUMMARY After the administration of [4-14C]lynestrenol (17α-ethynyl-19-nor-androst-4-en-17β-ol) to 7 human subjects 31·–57·6% of the dose, whether administered orally or i.v., was excreted in the urine within 5 days. The biological half-life of radioactivity was 26·5 hr. After acid and enzymatic hydrolysis, 58·7 and 45·6% respectively of the urinary radioactivity was extractable. About 10% of the urinary metabolites were excreted as sulphate conjugates. A mean value of 1·75% of the administered dose was converted to phenolic compounds. The metabolites in the free fraction and enzymehydrolysed extract of urine were almost entirely polar compounds, whereas 70% of the metabolites in the sulphate fraction were much less polar. The chromatographic evidence showed that hydroxylation of lynestrenol must have occurred at two points in the molecule. Plasma radioactivity decreased more rapidly than after administration of norethisterone.