Mefigest (Mifepristone) in Fertility and Gestational Health
Primary Uses
Mefigest (mifepristone) is NOT used to enhance or support fertility or gestational health—it is a progesterone receptor antagonist used primarily for pregnancy termination, emergency contraception, and cervical priming. 1, 2
Established Clinical Applications
Pregnancy Termination
- Mifepristone combined with prostaglandin analogues achieves 95% complete abortion rates in early pregnancy (up to 9 weeks gestation) when administered as 100-600mg single dose 36-48 hours before prostaglandin administration 2, 3
- The mechanism involves blocking progesterone receptors, which are essential for maintaining pregnancy 1, 2
- Mifepristone has a long half-life of 25-30 hours and is extensively metabolized by CYP3A4, with active metabolites contributing to its biological effects 1
Emergency Contraception
- Mifepristone 600mg as a single dose is highly effective for postcoital contraception within 72 hours of unprotected intercourse, with zero pregnancies reported in clinical trials 4
- It causes fewer side effects (40% nausea vs 60% with standard therapy, 3% vomiting vs 17%) compared to high-dose estrogen-progestogen regimens 4
- The main drawback is delayed onset of next menstrual period in 42% of users 4
Cervical Priming and Labor Induction
- Mifepristone effectively dilates the cervix prior to first-trimester vacuum aspiration 2, 5
- It facilitates second-trimester pregnancy termination by reducing prostaglandin dosage requirements and shortening the interval to termination 2
- Can be used to induce labor in cases of intrauterine fetal demise 2, 5
Critical Safety Considerations in Pregnancy
Contraindication During Desired Pregnancy
- If pregnancy occurs while on mifepristone (or similar antiprogestins), patients should be informed of possible increased risk of fetal malformations from first-trimester exposure, and pregnancy termination could be considered 6
- This parallels the guidance for tamoxifen exposure during pregnancy 6
Management of Early Pregnancy Loss
- Mifepristone combined with prostaglandin offers a medical alternative for management of miscarriages 3, 5
Other Gynecologic Applications (Not Fertility-Enhancing)
- Treatment of abnormal uterine bleeding 5
- Potential adjunct in gynecologic cancer treatment 5
- Investigational use in unresectable meningioma, metastatic breast cancer, and Cushing's syndrome 2
Key Clinical Pitfall
Do not confuse mifepristone with fertility-enhancing medications. Unlike clomiphene citrate or tamoxifen (which are selective estrogen receptor modulators used off-label for male infertility) 7, mifepristone is a progesterone antagonist that prevents or terminates pregnancy rather than supporting it. The drug's primary mechanism—blocking progesterone receptors—is fundamentally incompatible with maintaining pregnancy, as progesterone is essential for implantation and early gestational support 1, 4.