Antiprogestogen

Chemical structure of Mifepristone

Antiprogestogens are a class of drugs that act by inhibiting the effects of progesterone, a hormone crucial for the maintenance of pregnancy and the regulation of the menstrual cycle. These compounds are primarily used in medical abortion, emergency contraception, and the treatment of certain hormone-dependent conditions.

Mechanism of Action

Antiprogestogens work by binding to progesterone receptors in the body, thereby blocking the action of progesterone. This inhibition can lead to the breakdown of the endometrium, the inner lining of the uterus, and the detachment of the embryo in early pregnancy. In the context of the menstrual cycle, antiprogestogens can prevent the normal preparation of the endometrium for implantation.

Uses

Medical Abortion

Antiprogestogens, such as mifepristone, are commonly used in combination with misoprostol to induce medical abortion. Mifepristone is administered first to block progesterone, followed by misoprostol to induce uterine contractions and expel the pregnancy.

Emergency Contraception

In emergency contraception, antiprogestogens can be used to prevent pregnancy after unprotected intercourse. They work by delaying or inhibiting ovulation and altering the endometrial lining to prevent implantation.

Treatment of Hormone-Dependent Conditions

Antiprogestogens are also used in the treatment of conditions such as endometriosis, uterine fibroids, and certain types of breast cancer. By blocking progesterone, these drugs can reduce the growth of hormone-dependent tissues.

Side Effects

Common side effects of antiprogestogens include nausea, vomiting, abdominal pain, and fatigue. In some cases, they may cause heavy bleeding or infection following medical abortion. Long-term use can lead to bone density loss due to decreased estrogen levels.

Related Pages

• Progesterone
• Mifepristone
• Misoprostol
• Medical abortion
• Emergency contraception