ClinCalc Pro
Menu
Calculators Drugs Pathways AI Dx Donate Get the App
Antiprogestogen Pregnancy: Used in pregnancy specifically — for termination or management of early fetal loss

Mifepristone

Brand names: Mifegyne

Adult dose

Dose: Medical abortion (with misoprostol): 200 mg oral, followed 36–48h later by misoprostol 800 mcg vaginally/sublingually. Cervical ripening pre-operative: 200 mg oral 36–48h before procedure.
Route: Oral
Frequency: Single dose (always followed by misoprostol 36–48h later for TOP)
Max: 200 mg
Combined mifepristone + misoprostol: up to 98% effective for medical TOP up to 63 days (9 weeks) gestation. Used under licensed BPAS/NHS conditions. Never used alone for TOP.

Paediatric dose

Route: N/A
Frequency: N/A
Max: Not applicable
Not applicable in paediatric patients

Dose adjustments

Renal

No dose adjustment required

Hepatic

Avoid in severe hepatic impairment

Clinical pearls

  • Never prescribe mifepristone alone for TOP — must always be followed by misoprostol 36–48h later
  • UK Home Office: mifepristone can be taken at home under COVID-era regulations — maintained post-pandemic in England
  • Failure rate of medical TOP: 2–5% incomplete or ongoing pregnancy requiring surgical management
  • Mifepristone also used for cervical ripening before surgical procedures (termination or ERPC)

Contraindications

  • Ectopic pregnancy (absolute)
  • Anticoagulant therapy
  • Chronic adrenal failure
  • Inherited porphyria
  • Suspected incomplete miscarriage (relative)
  • Unknown IUD in situ (remove first)

Side effects

  • Nausea/vomiting
  • Abdominal cramps
  • Vaginal bleeding (expected)
  • Pelvic infection (rare)
  • Incomplete abortion requiring surgical intervention (2–5%)

Interactions

  • NSAIDs — may antagonise mifepristone via anti-prostaglandin mechanism (some protocols use NSAIDs — follow local guidance)
  • Anticoagulants — increased bleeding risk (contraindicated)

Monitoring

  • Confirmation of complete expulsion (transvaginal USS 2–3 weeks post-procedure or urine HCG)
  • Signs of infection (pyrexia, pelvic pain, offensive discharge)
  • Haemorrhage requiring intervention

Reference: BNFc; BNF; RCOG TOP Guidelines 2019; Faculty of Sexual and Reproductive Healthcare (FSRH). Verify against your local formulary and the latest BNF before prescribing.