Mifepristone
BNF entry: Mifepristone – always check latest guidance. Mifepristone is an antiprogestogenic steroid. Used in medical abortion, cervical ripening, and induction of labour in intra-uterine fetal death.
⚙️ Mode of Action
- Blocks progesterone receptors → decidual breakdown, detachment of gestational sac.
- Sensitises the myometrium to prostaglandin-induced contractions.
- Ripens the cervix, aiding expulsion.
💊 Indications & Typical Doses (Adults)
⚠️ Always confirm doses in BNF or local protocols – regimens differ internationally.
- Cervical ripening before surgical termination (≤84 days): 200 mg PO once, 36–48 h before procedure.
- Medical termination ≤49 days: 200–600 mg PO once, then misoprostol 400 mcg PO or gemeprost 1 mg PV after 36–48 h. Observe ≥3 h.
- Medical termination 50–63 days: 200–600 mg PO once, then misoprostol or gemeprost as above. Follow-up within 2 wks.
- Termination 13–24 weeks: 200–600 mg PO once, followed 36–48 h later by repeated prostaglandin (gemeprost 1 mg PV q3h, max 5 mg; or misoprostol). If failure after 24 h → repeat prostaglandin course.
- Missed miscarriage: 200 mg PO once, then misoprostol 800 mcg PV/PO/SL after 48 h.
- Induction of labour in intra-uterine fetal death (no uterine scar): 200 mg PO once, followed by dinoprostone or misoprostol per national guidance.
⚠️ Contraindications
- Acute porphyrias.
- Chronic adrenal failure.
- Uncontrolled severe asthma.
- Suspected ectopic pregnancy (requires alternative treatment).
- Allergy to mifepristone or excipients.
⚠️ Cautions
- Haemorrhagic disorders or anticoagulant use (↑ bleeding risk).
- Uterine scarring (risk of rupture with prostaglandins).
- Cardiovascular disease, anaemia, or heavy smoking.
- Close supervision required for all regimens.
🔄 Interactions
- CYP3A4 inhibitors (e.g. ketoconazole, erythromycin) ↑ mifepristone levels.
- CYP3A4 inducers (e.g. rifampicin, carbamazepine, phenytoin) ↓ effectiveness.
- Avoid concomitant corticosteroids – antagonises glucocorticoid activity.
💥 Side Effects
- Abdominal cramps, pelvic pain.
- Heavy vaginal bleeding (sometimes severe).
- Nausea, vomiting, diarrhoea.
- Headache, dizziness, hot flushes.
- Infection (endometritis, PID).
- Rare: uterine rupture, toxic shock, severe skin reactions (TEN, erythema nodosum).
📚 References
