Mifegyne (Mifepristone)

Mifegyne, a progesterone receptor antagonist, is employed in several obstetric contexts.

• Medical termination of early pregnancy: induces decidual breakdown and facilitates expulsion of the gestational sac.
• Management of miscarriage: promotes uterine evacuation when a miscarriage is incomplete.
• Cervical ripening prior to surgical abortion: softens the cervix to allow safer surgical procedures.

• Mifepristone binds competitively to progesterone receptors in the endometrium, blocking the hormone's action. This antagonism leads to decidual breakdown, detachment of the gestational sac, and sensitizes uterine smooth muscle to prostaglandins, enhancing uterine contractility and facilitating expulsion of pregnancy tissue.

Mifegyne may cause a range of adverse reactions, which are grouped by frequency.

Common Side Effects

• Abdominal pain: cramping or discomfort in the lower abdomen.
• Vaginal bleeding: spotting or heavier bleeding than a typical period.
• Nausea: feeling of queasiness or urge to vomit.
• Diarrhea: loose or watery stools.
• Headache: mild to moderate head pain.
• Fatigue: feeling unusually tired.

Serious or Rare Side Effects

• Severe infection: signs of sepsis or pelvic infection.
• Heavy bleeding: excessive hemorrhage requiring medical attention.
• Allergic reaction: rash, itching, swelling, or difficulty breathing.
• Liver dysfunction: jaundice or abnormal liver tests.
• Uterine rupture: rare but life‑threatening tearing of the uterus.

When using Mifegyne, several safety considerations are essential.

• Confirm gestational age: ensure pregnancy is within the approved timeframe for medical termination.
• Evaluate contraindications: exclude patients with chronic adrenal failure, long‑term corticosteroid therapy, or severe anemia.
• Assess for ectopic pregnancy: rule out non‑intrauterine implantation before administration.
• Review concomitant medications: consider potential drug interactions that may affect efficacy.
• Monitor for adverse reactions: observe patients for signs of heavy bleeding or infection.
• Store at room temperature: keep in the original pack, protect from moisture.

Mifegyne can interact with other medicines, requiring attention to the level of risk.

Major Interactions (Avoid)

• Rifampin: strong CYP3A4 inducer that may reduce mifepristone effectiveness.
• St. John’s wort: herbal CYP3A4 inducer potentially lowering drug levels.
• Antifungal azoles (e.g., ketoconazole): may increase mifepristone exposure and risk of toxicity.

Moderate Interactions (Monitor Closely)

• Warfarin or other anticoagulants: may enhance bleeding risk.
• NSAIDs: can increase gastrointestinal irritation and bleeding.
• SSRIs (selective serotonin reuptake inhibitors): may modestly affect hemostasis.