Mifepristone: English spelling of Mifepriston (progesterone antagonist)
Mifepristone is the English spelling of Mifepriston, a steroid with progesterone receptor antagonistic and partly glucocorticoid receptor antagonistic effects. Both forms refer to the same active substance. Internationally, the active substance is marketed under the trade names Mifegyne (Europe, France), Mifeprex (USA, formerly research name RU 486) and Korlym (Cushing indication) depending on the market.
Mifepriston was developed in France by Roussel Uclaf and first approved in 1988. The substance was internationally controversial for political, ethical and religious reasons, but has established itself as a safe and effective agent in modern reproductive medicine. The main indication in Europe is medical abortion in combination with misoprostol up to the 9th week of pregnancy, in the USA up to the 10th week. A special high-potency form (Korlym) is used in the USA for Cushing syndrome.
Mechanism of action
Mifepriston binds with higher affinity to the progesterone receptor than progesterone itself and acts as a competitive antagonist there. It additionally binds to the glucocorticoid receptor and to a lesser extent to the androgen receptor. The antiprogestational effect is the clinically most relevant.
In early pregnancy, progesterone receptor antagonism leads to destabilization of the decidua, separation of the oocyte from the endometrium and increased sensitivity of the uterus to prostaglandins. Following administration of misoprostol (synthetic prostaglandin E1 analogue), uterine contractions occur and abortion results.
In Cushing syndrome, mifepriston blocks the glucocorticoid receptor and counteracts hypercortisolism without lowering cortisol levels themselves. This complicates diagnostics as cortisol levels remain elevated.
Pharmacokinetically, mifepriston is well absorbed orally (bioavailability approximately 70 percent), half-life approximately 18 hours, metabolized via CYP3A4. Active metabolites prolong the effect.
Indications
- Medical abortion: up to the 9th week of pregnancy (Europe) or 10th week (USA), in combination with misoprostol
- Cervical preparation before surgical abortion: facilitates dilation
- Acceleration of labor in intrauterine fetal death: in specialized obstetric centers
- Emergency contraception (very low dose): historical and off label, displaced by ulipristal
- Cushing syndrome (USA, Korlym): in hyperglycemia due to endogenous hypercortisolism, when surgery is not possible
- Off label: endometriosis, uterine fibroids, meningiomas (in research)
Dosage and administration
Medical abortion: 200 mg mifepriston orally as a single dose, followed by 800 micrograms misoprostol buccal, sublingual or vaginal after 24 to 48 hours. Efficacy is over 95 percent up to the 9th week. A follow-up examination 1 to 2 weeks later confirms complete abortion.
Cushing syndrome (Korlym in the USA): Initially 300 mg daily, increase up to maximum 1.200 mg daily.
Counseling obligation: Medical abortion in Germany requires prior psychosocial counseling in a state-approved counseling center in accordance with section 218 StGB and a three-day waiting period. Mifepriston may only be dispensed in approved facilities, not in the pharmacy.
Adverse effects
Very common (in the context of abortion): Vaginal bleeding (over 95 percent, may last several days), abdominal pain and cramps (over 80 percent), nausea, vomiting, diarrhea, fatigue, dizziness.
Common: Headaches, rash, fever, prolonged spotting over several weeks.
Uncommon to rare: Heavy bleeding with hemoglobin drop (approximately 1 percent), incomplete abortion requiring surgical intervention (approximately 2 to 5 percent), infection (endomyometritis), allergic reactions.
Serious, very rare: Fatal septic shock from Clostridium sordellii (especially reported with vaginal misoprostol application), severe hemorrhage requiring blood transfusion or hysterectomy (very rare).
Important: Patients are informed about warning symptoms: heavy bleeding (more than 2 thick pads per hour for 2 hours), severe abdominal pain for several days, high fever, foul-smelling discharge. These symptoms require immediate medical attention.
Drug interactions
- Strong CYP3A4 inhibitors (ketoconazole, itraconazole, erythromycin, HIV protease inhibitors): increased mifepriston levels
- Strong CYP3A4 inducers (rifampicin, carbamazepine, phenytoin, St. John's wort): reduced mifepriston effect
- NSAIDs (aspirin, ibuprofen, naproxen): theoretical antagonism to misoprostol; clinically not clearly relevant, in most protocols NSAIDs are still used as analgesics
- Glucocorticoids: Mifepriston antagonizes their effect, important in patients on cortisol substitution or asthma therapy
- Anticoagulants: increased bleeding risk
Special notes
Legal framework in Germany: Abortion is in principle punishable under section 218 StGB, but remains non-prosecutable under certain conditions (counseling regulation, medical or criminological indication). Abortion is only permissible after legally required counseling and waiting period. Mifepriston is obtained exclusively in approved facilities from wholesale stocks.
Contraindications: Confirmed ectopic pregnancy (mifepriston does not work), uncontrolled asthma, chronic renal insufficiency, porphyria, bleeding disorders, long-term glucocorticoid therapy, suspected mifepriston allergy.
Patient support: Medical abortion takes place at home, but should be accompanied by a trusted person. Accessibility to the medical facility must be ensured.
Follow-up care: 1 to 2 weeks after mifepriston/misoprostol administration, follow-up examination with clinical assessment, hormone determination (beta hCG) and ultrasound to confirm complete abortion.
Contraception afterwards: Fertility returns very quickly, reliable contraception should begin immediately after abortion if desired.
You might also be interested in
- Mifepriston, German spelling with detailed pillar page
- Misoprostol, prostaglandin combination partner
- Ulipristal, another progesterone receptor modulator (emergency contraception)
- Levonorgestrel, standard emergency contraception
- Oxytocin, labor hormone in obstetrics
Frequently asked questions
Is Mifepristone the same as Mifepriston?
Yes. Mifepristone is the English spelling (e at the end), Mifepriston the German form. Both refer to the same active substance (ATC G03XB01), a progesterone receptor antagonist.
How safe is medical abortion?
With correct use in the early phase of pregnancy (up to the 9th week), the method is very safe and efficacy rates are over 95 percent. Serious complications such as heavy bleeding or infections occur in less than one percent of cases. The method is significantly safer than a full-term pregnancy with normal labor.
How long does the procedure take?
Mifepriston is taken as a single dose, followed by misoprostol administration after 24 to 48 hours. Bleeding usually begins within a few hours and lasts several days to weeks. Most patients experience abortion within 4 to 6 hours after misoprostol, with crampy abdominal pain, bleeding and passage of pregnancy material.
Does mifepriston affect my future fertility?
No. Studies have shown that medical abortion has no impact on future fertility, risk of preterm birth or possibility of normal pregnancy. Fertility returns very quickly, often already in the next cycle, which is why reliable contraception should begin immediately if no further pregnancy is desired.
Sources
- EMA expert information Mifegyne
- DGGG recommendations on medical abortion
- BfArM, Federal Institute for Drugs and Medical Devices
- WHO Guidelines on Medical Management of Abortion
Legal notices and disclaimer
The information provided on this page is for general information purposes only and does not constitute medical advice, diagnosis or treatment recommendation. It does not replace the advice of a licensed physician or pharmacist. Medicines should always only be taken on the prescription of a physician or pharmaceutical dispensing. All information is based on expert information published at the time of creation and recognized scientific sources; the current expert information of the manufacturer is always authoritative. Sanoliste assumes no liability for completeness, timeliness or accuracy of the information presented. In a medical emergency, call the emergency number 112.