TY - JOUR T1 - STEREOSELECTIVE BIOTRANSFORMATIONS OF <em>dl</em>-NORGESTREL AND ITS ENANTIOMERS IN THE AFRICAN GREEN MONKEY JF - Drug Metabolism and Disposition JO - Drug Metab Dispos SP - 65 LP - 70 VL - 2 IS - 1 AU - SAMUEL F. SISENWINE AU - HAZEL B. KIMMEL AU - ANN L. LIU AU - HANS W. RUELIUS Y1 - 1974/01/01 UR - http://dmd.aspetjournals.org/content/2/1/65.abstract N2 - 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 ER -