Progestogen antagonists

Indications Medical termination of intrauterine pregnancy Category Corticosteroid antagonist Progestogen antagonist Half-life 20 hours... 

Antiandrogens such as cyproterone acetate (5.54) or the nonsteroidal flutamide (5.55, a substituted anilide) are competitive antagonists on the cytosol receptor. They do not prevent DHT formation rather, they inhibit the nuclear retention of DHT in the prostate. They cause feminization in male fetuses and decrease libido in males. Cyproterone is also an active progestogen. In men, antiandrogens are used commonly in the treatment of prostatic cancer and uncommonly to inhibit sex drive in hypersexuality in women, antiandrogens are used to treat virilization. Bicalutamide (5.56) and nilutamide (5.57) are potent, orally active antiandrogens that may be used in the treatment of metastatic prostate carcinoma. 

ACE INHIBITORS, ANGIOTENSIN II RECEPTOR ANTAGONISTS PROGESTOGENS t risk of hyperkalaemia Drospirenone (component of the Yasmin brand of combined contraceptive pill) is a progestogen derived from spironolactone that can cause potassium retention Monitor serum potassium weekly until stable, then eveiy 6 months... 

Sex hormones and hormone antagonists. Oestrogens increase the synthesis of some vitamin K dependent clotting factors and progestogen-only contraceptives are preferred. The hormone antagonists danazol, flutamide and tamoxifen enhance the effect of warfarin. 

Selectivity. Many synthetic analogues, although classed as, e.g. androgen, anabolic steroid, progestogen, are nonselective and bind to several types of receptor as agonist, partial agonist, antagonist. 

Plainly oestrogens and progestogens are physiological antagonists to androgens. But compounds which compete selectively for androgen receptors have been made. 

R13615) is a synthetic steroid, a PROGESTOGEN, and has been used in HRT. It has also been used in anticancer treatment of prostate and breast cancer, medroglutaric acid meglutol. medroxalol [ban, inn, usan] (medroxalol hydrochloride [usan]) is a combined O-adrenoceptor ANTAGONIST and P-adrenoceptor ANTAGONIST. It can be used therapeutically as an ANTIHYPERTENSIVE. 

Peterson CM. Progestogens, progesterone antagonists, progesterone, and androgens synthesis, classification, and uses. Clin Obstet Gynecol 1995 38 813-820. 

---