Last reviewed 2026-04-20 · How we verify

Mifeprex (MIFEPRISTONE)

Mifeprex works by blocking the action of progesterone, a hormone that helps maintain pregnancy.

Mifeprex (Mifepristone) is a small molecule progestin antagonist developed by Danco Labs LLC and currently owned by Corcept Therapeutics. It targets the glucocorticoid receptor and is FDA-approved since 2000 for the treatment of pregnancy with an abortive outcome. Mifeprex is available as a branded product and has three generic manufacturers. The drug has a half-life of 16.6 hours and a bioavailability of 69%. Key safety considerations include its potential to cause adrenal insufficiency and other hormonal imbalances.

At a glance

Mechanism of action

Mifepristone is selective antagonist of the progesterone receptor at low doses and blocks the glucocorticoid receptor (GR-II) at higher doses. Mifepristone has high affinity for the GR-II receptor but little affinity for the GR-I (MR, mineralocorticoid) receptor. In addition, mifepristone appears to have little or no affinity for estrogen, muscarinic, histaminic, or monoamine receptors.

Approved indications

• Pregnancy with abortive outcome

Boxed warnings

• WARNING: TERMINATION OF PREGNANCY Mifepristone is a potent antagonist of progesterone and cortisol via the progesterone and glucocorticoid (GR-II) receptors, respectively. The antiprogestational effects will result in the termination of pregnancy. Pregnancy must therefore be excluded before the initiation of treatment with KORLYM and prevented during treatment and for one month after stopping treatment by the use of a non-hormonal medically acceptable method of contraception unless the patient has had a surgical sterilization, in which case no additional contraception is needed. Pregnancy must also be excluded if treatment is interrupted for more than 14 days in females of reproductive potential. WARNING: TERMINATION OF PREGNANCY See full prescribing information for complete boxed warning. Mifepristone has potent antiprogestational effects and will result in the termination of pregnancy. Pregnancy must therefore be excluded before the initiation of treatment with KORLYM, or if treatment is interrupted for more than 14 days in females of reproductive potential.

Common side effects

• Nausea
• Weakness
• Fever/chills
• Vomiting
• Headache
• Diarrhea
• Dizziness
• Transfusion
• Sepsis
• ER visit
• Hospitalization Related to Medical Abortion
• Hemorrhage

Drug interactions

• High Risk QT Prolonging Agents
• P-glycoprotein Substrates
• alfentanil
• boceprevir
• celecoxib
• ciclosporin
• clarithromycin
• conivaptan
• dienestrol
• diethylstilbestrol
• estradiol
• ethinylestradiol

Key clinical trials

• Simultaneous Mifepristone and Misoprostol Versus Misoprostol Alone for Induction of Labor of Nonviable Second Trimester Pregnancy: a Pilot Randomized Controlled Trial (PHASE4)
• A Study of Enzalutamide, Enzalutamide in Combination With Mifepristone, or Chemotherapy in People With Metastatic Breast Cancer (PHASE2)
• A Real-World Study Comparing the Efficacy of Different Treatment Regimens for Early Missed Abortion (NA)
• Study of Pembrolizumab and Mifepristone in Patients With Advanced HER2-negative Breast Cancer (PHASE2)
• The Misoprostol-Only Regimen Evidence Study (PHASE4)
• Efficacy, Safety, and Acceptability of Mifepristone 50 mg Once-weekly as a Contraceptive (PHASE3)
• Mifepristone Outpatient Labour Induction (PHASE2)
• Mifepristone vs Misoprostol (PHASE1)

Patents

Primary sources

Every claim on this page is sourced from regulatory or scientific primary sources. See our editorial policy for full methodology.