RU-486 as an Antiprogesterone Steroid

Abstract

The steroid RU-486 (mifepristone) is an antiprogesterone that works at the receptor level. It can interrupt pregnancy very early on (contragestion), mostly by interfering with the process of implantation and decidua function. It also may facilitate surgical evacuation of the uterus and certain difficult deliveries. It impedes ovulation when taken during the follicular phase. Also, RU-486 is the first antiglucocorticosteroid available for clinical use. It deserves further studies to assess its wide range of therapeutic potential.

Progesterone is not the same as 17α-hydroxyprogesterone caproate: implications for obstetrical practice

“…The findings of Csapo et al were buttressed by the observation that progesterone receptor blockade leads to early pregnancy loss (eg, RU-486 or mifepristone administration). 20-23 Moreover, the administration of RU-486 to pregnant women in the third trimester results in cervical ripening and often the onset of labor. 24-27 …”

Estrogen and Progesterone Receptors in the Endometrium

“…Antiprogestins can also be classified into pure antagonists, such as ZK98299, and partial agonists, such as RU486 28 . It is generally assumed that the former prevent binding of the receptor to DNA, whereas the latter enable DNA binding of the receptor, but in a form unable to activate the hormone‐responsive genes.…”

The stalled revolution of contraception

“…The most significant research achievement so far is the anti-progestin, Mefipristone (RU-486), which was developed in France by E. Baulieu in 1986 [5]. It has promptly been labeled the "French Death Pill" by anti-abortionists in the US, because it prevents implantation of the fertilized ovum in the endometrium, the inner lining of the womb, rather than the actual fertilization and can thus be classified as an "abortificiant".…”