Is there a role for antiestrogens (estrogen antagonists) in the regulation of fertility?

Centchroman, a selective estrogen receptor modulator, as a contraceptive and for the management of hormone-related clinical disorders

DL-Centchroman (67/20; INN: Ormeloxifene) synthesized at the Central Drug Research Institute, Lucknow, is a nonsteroidal once-a-week oral contraceptive. It was introduced in Delhi in July, 1991, marketed in India in 1992 as Saheli and Choice-7 (Hindustan Latex Ltd., Thiruvananthapuram) and Centron (Torrent Pharmaceuticals India Ltd., Ahmedabad), and included in the National Family Welfare Programme in 1995.5 According to post-marketing surveillance, approximately 100,000 women were using this pill and approximately 1100,000 menstrual cycles were covered until 1996. It is a unique need-oriented contraceptive being effective when taken immediately after coitus or routinely as a weekly pill and has the advantage of less frequent administration. Its contraceptive action is quickly reversible. It has long terminal serum halflife of 168 hr in women and exhibits duration of anti-implantation/estrogen antagonistic action of 120 hr, despite a short (24.1 hr) serum halflife, in the rat. In lactating women, it is excreted in milk in quantities considered unlikely to cause any deleterious effect on suckling babies. In phase II and III multicentric trials as a contraceptive, children born of method-and-user failure pregnancies showed normal milestones, without any congenital anomaly. Reports of its promising action in the management of certain hormone-related clinical disorders are available. It has an excellent therapeutic index and is considered safe for chronic administration.

Effect of CDRI-85/287 on uterine estradiol and progesterone receptor levels/morphometric measurements during preimplantation period in rat

Studies with 85/287, a potent nonsteroidal antiestrogen/antiimplantation agent were taken up. In this paper we report alterations in uterine morphometric measurements and estrogen/progesterone receptor levels under the influence of this compound. Results showed 32% decline in stromal absolute volume density on day 5 post-coitum (p.c.) only, whereas eosinophilic leucocyte number decreased both on days 3 and 5 p.c. (41%) in treated rat uterus. Epithelial mitotic activity showed complete cessation both in control and treated rats on day 5 p.c. Under the influence of the compound both cytosolic and nuclear estrogen receptor (ERc and ERn) levels decreased on day 3 p.c., but on day 5 p.c. ERn increased significantly. A significant increase was however noticed in progesterone nuclear receptors (PRn) on day 5 p.c. On the whole our studies showed overall significant changes in uterine morphometric measurement/estrogen and progesterone receptor levels during the preimplantation period in rat under the influence of compound 85/287, causing asynchrony of events and thus failure of implantation.

Effect of a specific estrogen antibody on pregnancy establishment in the bonnet monkey (Macaca radiata)

The requirement for estrogen for pregnancy establishment has not been conclusively demonstrated in primates. Selective neutralization of estrogens was achieved in mated female monkeys during preimplantation and postimplantation periods by injecting characterized estrogen antiserum from either day 14 to 18 or day 28 to 32 of cycle. While estrogen deprivation during preimplantation period in 5 animals exposed to 14 ovulatory cycles resulted in only one pregnancy, only 3 of 13 monkeys treated during postimplantation period continued pregnancy to term. In comparison with controls (4 of 5 monkeys becoming pregnant), the percent protection against pregnancy in animals treated during preimplantation period was 93. The pregnancy termination in 10 of 13 monkeys treated during postimplantation period when compared with normal postimplantation pregnancy wastage in our colony (2%) is also highly significant (P less than 0.01). The present study demonstrates a critical need for estrogen during the peri-implantation period for a successful pregnancy establishment in primates.