RT Journal Article SR Electronic T1 STEREOSELECTIVE BIOTRANSFORMATIONS OF dl-NORGESTREL AND ITS ENANTIOMERS IN THE AFRICAN GREEN MONKEY JF Drug Metabolism and Disposition JO Drug Metab Dispos FD American Society for Pharmacology and Experimental Therapeutics SP 65 OP 70 VO 2 IS 1 A1 SAMUEL F. SISENWINE A1 HAZEL B. KIMMEL A1 ANN L. LIU A1 HANS W. RUELIUS YR 1974 UL http://dmd.aspetjournals.org/content/2/1/65.abstract AB The comparative metabolism of dl-, d-, and l-norgestrel was investigated in African Green Monkeys (Cercopithecus aethiops). Total 14C excretion in urine after a single oral dose of 14C-dl-norgestrel (1 mg/kg) was significantly higher (51.4 ± 5.0%) than that observed after administration of the d-enantiomer (37.5 ± 5.4%) but not the l-enantiomer (44.2 ± 8.9%). In all cases, the major part of the urinary radioactivity was present in a free fraction (48-62%), while an additional 13-27% was released by β-glucuronidase preparations. No sulfate conjugates were detected. At least one major (16β-hydroxylation) and one minor (16α-hydroxylation) metabolic pathway were stereoselective, i.e., they are operative with the I-but not the d-enantiomer. Three metabolites, 16β-hydroxynorgestrel, 16α-hydroxynorgestrel, and 16-hydroxytetrahydronorgestrel (believed to be 16β) were only detected in urine samples obtained from 14C-dland -l-norgestrel-dosed animals. Following 14C-d-norgestrel administration, 3α, 5β-tetrahydronorgestrel was found to be the major urinary metabolite. These observations are compared with those reported earlier on the urinary metabolites of dl-norgestrel in women. Copyright © 1974 by The American Society for Pharmacology and Experimental Therapeutics