Metabolism of D- and L-norgestrel in humans.
Levels of DL-norgestrel, D-norgestrel, L-norgestrel and norethisterone were measured in blood by radioimmunoassay after oral administration of the progestin to 3 healthy male subjects and the half-lives calculated. Half-lives for D-norgestrel were much lower than those of L-norgestrel and similar to those of norethisterone. Measurement of norgestrel in blood can therefore be misleading unless the biologically active D-isomer is estimated. Since there was no difference in half-lives between norgestrel and norethisterone the greater potency of the former is probably due to it more strongly binding to target organ receptors.
D006207:Half-Life; D006801:Humans; D008297:Male; D009640:Norethindrone / Q000097:blood; D009644:Norgestrel / Q000097:blood*; D011956:Receptors, Cell Surface; D013237:Stereoisomerism
D011956:Receptors, Cell Surface; D009644:Norgestrel; D009640:Norethindrone