Steroid methoximes I: Antifertility activity of methoxime derivatives of progesterone, estrone and 16-ketoestradiol in the rat.

Antifertility activity of methoxime derivatives of progesterone, est rone, and 16-ketoestradiol was studied in the rat. None of the 3 proges terone derivatives (progesterone-3-methoxime, progesterone-20-methoxime, and progesterone-3,20-dimethoxime) administered in daily doses up to 1 mg/animal showed any antifertility activity in female rats during the mating studies. And only progesterone-20-methozime displaced the parent steroid from the guinea pig uterine receptor. The 3 derivatives had no antifertility effect. An sc dose of 100 mcg of estrone-17-methoxime/day suppressed fertility whereas only 3 mcg of the estrone achieved the same result. However, when administered orally the compounds were similarly effective which indicates that methoxime is well abosrbed from the gastrointestinal tract. Uterine growth assay revealed the potency of estrone to be 30 times that of the methoxime. It appears that estrone-17-methoxime owes its antifertility activity to its estrogenic properties rather than to any antagonizing effect.