Mifepristone has now been approved by the TGA for use prior to misoprostol in the medical termination of pregnancy in Australia; 2 months after the European Medicines Agency extended marketing authorisation to all Member States of the EU, and 12 years after its FDA approval in the USA.
Mifepristone is a synthetic steroid which competitively inhibits the endometrial and myometrial effects of progesterone and sensitises the myometrium to the contractile effects, and first trimester cervical dilatation, of prostaglandins (misoprostol).
Contraindications include chronic adrenal failure, severe disease such as uncontrolled asthma, inherited porphyria, and suspected ectopic pregnancy. There is insufficient data to advise on safety in renal or hepatic failure; or the risk of teratogenicity if the pregnancy proceeds.
Follow up consultation is necessary to confirm expulsion, even with bleeding of up to 16 days.
Elimination is primarily by slow metabolism by CYP3A4, and may demonstrate two-way inhibition with other drugs using the same pathway; or be induced by rifampicin, dexamethasone, St John’s Wort, and some anticonvulsants.
Headache, bleeding, fatigue, chills, fever, and gastrointestinal adverse effects are common. Fatal sepsis has been reported, usually from Clostridium sordellii, and stomach pain or discomfort, weakness, nausea, vomiting or diarrhoea with or without fever, which develop 24 hours after taking the misoprostol should be investigated.
Other potential uses for mifepristone include the treatment of breast cancer, Cushing’s syndrome, endometriosis, glaucoma, meningioma, ovarian cancer, prostate cancer and uterine fibroids.