Antiprogestogens, or antiprogestins, also known as progesterone antagonists or progesterone blockers, are a class of

drug A drug is any chemical substance that causes a change in an organism's physiology or psychology when consumed. Drugs are typically distinguished from food and substances that provide nutritional support. Consumption of drugs can be via inhal ...

s which prevent

progestogen Progestogens, also sometimes written progestagens or gestagens, are a class of natural or synthetic steroid hormones that bind to and activate the progesterone receptors (PR). Progesterone is the major and most important progestogen in the bod ...

s like

progesterone Progesterone (P4) is an endogenous steroid and progestogen sex hormone involved in the menstrual cycle, pregnancy, and embryogenesis of humans and other species. It belongs to a group of steroid hormones called the progestogens and is the ma ...

from mediating their

biological effect In evolutionary biology, function is the reason some object or process occurred in a system that evolved through natural selection. That reason is typically that it achieves some result, such as that chlorophyll helps to capture the energy of s ...

s in the body. They act by blocking the

progesterone receptor The progesterone receptor (PR), also known as NR3C3 or nuclear receptor subfamily 3, group C, member 3, is a protein found inside cells. It is activated by the steroid hormone progesterone. In humans, PR is encoded by a single ''PGR'' gene res ...

(PR) and/or inhibiting or suppressing progestogen production. Antiprogestogens are one of three types of sex hormone antagonists, the others being

antiestrogen Antiestrogens, also known as estrogen antagonists or estrogen blockers, are a class of drugs which prevent estrogens like estradiol from mediating their biological effects in the body. They act by blocking the estrogen receptor (ER) and/or i ...

s and

antiandrogen Antiandrogens, also known as androgen antagonists or testosterone blockers, are a class of drugs that prevent androgens like testosterone and dihydrotestosterone (DHT) from mediating their biological effects in the body. They act by blocking the ...

s. Antiprogestogens are used as

abortifacient An abortifacient ("that which will cause a miscarriage" from Latin: '' abortus'' "miscarriage" and '' faciens'' "making") is a substance that induces abortion. This is a nonspecific term which may refer to any number of substances or medications ...

s and

emergency contraceptive Emergency contraception (EC) is a birth control measure, used after sexual intercourse to prevent pregnancy. There are different forms of EC. Emergency contraceptive pills (ECPs), sometimes simply referred to as emergency contraceptives (ECs), ...

s and in the treatment of

uterine fibroid Uterine fibroids, also known as uterine leiomyomas or fibroids, are benign smooth muscle tumors of the uterus. Most women with fibroids have no symptoms while others may have painful or heavy periods. If large enough, they may push on the bla ...

s. They are also being studied in the treatment of

breast cancer Breast cancer is cancer that develops from breast tissue. Signs of breast cancer may include a lump in the breast, a change in breast shape, dimpling of the skin, milk rejection, fluid coming from the nipple, a newly inverted nipple, or ...

. Examples of antiprogestogens include the

weak

partial agonist In pharmacology, partial agonists are drugs that bind to and activate a given receptor, but have only partial efficacy at the receptor relative to a full agonist. They may also be considered ligands which display both agonistic and antagonist ...

mifepristone Mifepristone, also known as RU-486, is a medication typically used in combination with misoprostol to bring about a medical abortion during pregnancy and manage early miscarriage. This combination is 97% effective during the first 63 days of ...

, the selective progesterone receptor modulator (SPRM)

ulipristal acetate Ulipristal acetate, sold under the brand name Ella among others, is a medication used for emergency contraception (birth control) and uterine fibroids. As emergency contraception it should be used within 120 hours of vaginally penetrating inter ...

, and the silent antagonist aglepristone. For medical abortion, mifepristone is combined with a

prostaglandin The prostaglandins (PG) are a group of physiologically active lipid compounds called eicosanoids having diverse hormone-like effects in animals. Prostaglandins have been found in almost every tissue in humans and other animals. They are der ...

(e.g., gemeprost). Several hundred antiprogestogens have been developed, but only three,

, lilopristone, and onapristone, have been given to humans, and of these, only mifepristone has been approved and introduced for clinical use.

References

External links

*
Antiprogestin
entry in the public domain NCI Dictionary of Cancer Terms {{genito-urinary-drug-stub

See also

References

External links