Abstract
Summary
Norethindrone (17α-ethynyl-17β-hydroxyestr-4-en-3-one) (estrogen-free) is 0.3% as active as estrone by gavage and by subcutaneous injection by a mouse uterotrophic assay. This steroid, free of estrogens, is about 3 to 5 times more active than previously studied material containing an estrogen contaminant. Both materials exhibit the same progestational activity when administered orally in the Clauberg assay and when studied in an oral rabbit anti-ovulation assay. Norethindrone (estrogen-free) has been studied in castrated female-intact female and castrated male-intract female parabiotic pairs in a rat spermatogenesis inhibition test, and in the pregnant rat.
Get full access to this article
View all access options for this article.