Antiprogestins: Classification, Mechanism, Uses, and Effects

Classification

Inhibition of progesterone receptor: Antiprogestins bind to the progesterone receptor, preventing the normal action of progesterone.
Endometrial changes: The drug inhibits endometrial development, making the uterine lining unsuitable for implantation.
Cervical softening and myometrial contraction: Promotes cervical dilation and uterine contractions, especially useful in medical abortion.

Medical abortion: Mifepristone is used in combination with misoprostol to induce abortion within the first 10 weeks of pregnancy.
Emergency contraception: Ulipristal acetate is taken within 72 hours after unprotected intercourse to prevent pregnancy.
Fibroids treatment: Mifepristone can reduce uterine fibroid size by blocking progesterone.
Endometriosis: Antiprogestins may be used to manage endometriosis symptoms.

Common side effects: Nausea, vomiting, abdominal pain, fatigue, dizziness, headache, and breast tenderness.
Bleeding and spotting: Vaginal bleeding may occur, especially during medical abortion or use of emergency contraception.
Endometrial changes: Prolonged use may lead to endometrial hyperplasia or atrophy.
Gastrointestinal disturbances: Diarrhea or constipation may be experienced by some individuals.

Ectopic pregnancy: Antiprogestins should not be used in cases of ectopic pregnancy as they can worsen the condition.
Chronic adrenal failure: Mifepristone is contraindicated in patients with adrenal insufficiency.
Hypersensitivity: Known allergy to antiprogestins or any of their components.
Severe liver or renal dysfunction: These conditions can increase the risk of toxicity due to altered drug metabolism.
Undiagnosed vaginal bleeding: It is crucial to rule out abnormal vaginal bleeding before using mifepristone for medical abortion.

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