title: Antiprogesterone effect and midcycle (periovulatory) contraception.
abstract: Based on the sequential changes of hormones in plasma and of progesterone binding sites in the uterus, it is suggested to give once a month, at midcycle (around ovulation), either progesterone itself or a parent compound binding to progesterone receptor. The aim is an antiprogesterone effect occurring presumably through a decrease of receptor functioning ultimately expressed some days later by lack of implantation.
mesh_terms: D000818:Animals; D003278:Contraceptives, Oral, Hormonal / Q000494:pharmacology*; D010064:Embryo Implantation / Q000187:drug effects; D004967:Estrogens / Q000494:pharmacology; D005260:Female; D006168:Guinea Pigs; D006801:Humans; D010060:Ovulation; D011374:Progesterone / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D011980:Receptors, Progesterone / Q000187:drug effects*; D014599:Uterus / Q000187:drug effects
chemical_list: D003278:Contraceptives, Oral, Hormonal; D004967:Estrogens; D011980:Receptors, Progesterone; D011374:Progesterone