Mifegyne (Mifepristone)

Mifepristone, a progesterone receptor antagonist, is used in reproductive and endocrine conditions where progesterone signaling plays a key role.

• Medical termination of intrauterine pregnancy (up to 10 weeks gestation): induces decidual breakdown, enhances uterine contractility, and facilitates expulsion of the gestational sac when combined with prostaglandin analogues.
• Uterine fibroids (off‑label): may reduce fibroid volume, decrease menstrual bleeding, and improve pelvic discomfort in selected patients.
• Cushing's syndrome (off‑label): contributes to cortisol reduction by antagonizing progesterone receptors that influence adrenal steroidogenesis, supporting other therapeutic measures.

• Mifepristone binds with high affinity to the progesterone receptor, acting as a selective antagonist that blocks progesterone‑mediated transcription. This inhibition leads to decidual breakdown, loss of uterine support for the embryo, and sensitization of the myometrium to prostaglandins, thereby promoting uterine contractions and expulsion of the gestational tissue. The drug also exhibits weak glucocorticoid receptor antagonism, which can contribute to its effects in endocrine disorders such as Cushing's syndrome.

Mifepristone may cause a spectrum of adverse reactions, ranging from mild to potentially life‑threatening.

Common Side Effects

• Nausea: mild to moderate gastrointestinal upset.
• Vaginal bleeding: irregular or heavy bleeding after administration.
• Cramping: uterine cramping or lower abdominal pain.
• Fatigue: general tiredness or weakness.

Serious or Rare Side Effects

• Severe infection: signs of sepsis or pelvic infection requiring urgent care.
• Heavy hemorrhage: excessive blood loss that may need transfusion.
• Allergic reaction: rash, swelling, or anaphylaxis.

Prior to prescribing Mifepristone, clinicians should evaluate several safety considerations to minimize risk.

• Contraindication: pregnancy beyond 10 weeks gestation or ectopic pregnancy.
• Medical supervision: administration must occur under a qualified health‑care provider.
• Cardiac risk: avoid in patients with uncontrolled hypertension or significant cardiovascular disease.
• Liver function: monitor hepatic enzymes in patients with known liver impairment.
• Drug interactions: review concomitant medications, especially CYP3A4 inducers or inhibitors.
• Store at ambient temperature: keep below 25 °C, retain in original packaging, and protect from moisture.

Mifepristone's metabolism and pharmacodynamic profile can be altered by concomitant medicines, necessitating careful review.

Major Interactions (Avoid)

• CYP3A4 inducers (e.g., rifampin, carbamazepine): may markedly reduce therapeutic effect.
• Antifungal azoles (e.g., ketoconazole): may increase plasma concentrations and risk of toxicity.

Moderate Interactions (Monitor Closely)

• Anticoagulants (e.g., warfarin): may enhance bleeding risk.
• NSAIDs: may increase gastrointestinal irritation.
• Hormonal contraceptives: may reduce contraceptive efficacy when used concurrently.