Possible Interaction: Norethindrone and Progesterone

“ NET is a compound with five- to eight-fold weaker PR binding and transactivation activities than the reference compound Org 2058 (100%) and two-fold stronger than progesterone.”

“During treatment with norethindrone, progesterone levels decreased.”

“A comparison of the levels of these steroids between untreated controls (LH + 8 to + 11) and norethisterone-treated women demonstrated that the progesterone levels in peritoneal fluid were highly reduced by norethisterone treatment, while the oestradiol levels were not affected.”

“ Norethisterone treatment significantly reduced the peritoneal fluid volume as well as its progesterone concentration, whereas the oestradiol and gonadotrophin levels remained unchanged.”

“Oral administration of norethindrone significantly reduced the cytoplasmic and nuclear receptor concentration for estradiol and progesterone.”

“ Norethindrone (17beta-hydroxy-19-nor-17alpha-pregn-4-en-20-yn-3-one) and norethindrone acetate (17beta-acetoxy-19-nor-…-pregn-4-en-20-yn-3-one) interfered to a varying degree, by competitive inhibition, with the binding of progesterone and oestradiol to respective cytoplasmic … in the human uterus.”

“The strongest inhibition on progesterone formation was induced by Δ 4 -3-keto-19-nortestosterone derivatives, norethisterone and methylestrenolone.”

“.5 mg of norethindrone depressed the levels of LH progesterone and pregnanediol and the decomposition of estrogens was increased.”

“In contrast, progesterone alone had no effect, in young intact or adult castrated males, but norethindrone did stimulate mammary growth.”

“The overall results suggest that NET metabolites exert antiimplantation and antiprogestational effects through their interaction with progesterone and estrogen receptors, and provide an explanation for the molecular mechanisms involved in the postcoital contraceptive action of NET.”

“Binding of radiolabeled progesterone by receptors at pH 6.4 was highly inhibited by the progesterone analogs 3,5-seco-4-norpregnan-5-on-3-oic acid and 19-norethisterone or 21-deoxycorticosterone.”