Estradiol and Mifepristone: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Mifepristone
Estradiol
How we grade severity & evidence
Severity levels
- Contraindicated: These should generally not be used together.
- Major: Potentially serious — often needs a change or close monitoring.
- Moderate: Can be significant — usually manageable with monitoring.
- Minor: Usually limited clinical impact.
Evidence grades
- Established: Well documented — supported by controlled studies or strong clinical data.
- Probable: Good supporting evidence, though not definitively proven.
- Suspected: Some evidence suggests this interaction, but it is not well established.
- Possible: Limited or conflicting evidence; the interaction may occur.
- Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.
Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.
What happens
Reduced hormonal contraceptive exposure, an increased miFEPRIStone exposure and an increased hormonal contraceptives exposure
Interaction Deep Dive
MiFEPRIStone is a progesterone-receptor antagonist and will interfere with the effectiveness of hormonal contraceptives. Therefore, use non-hormonal contraceptive methods. Additionally, concomitant use of miFEPRIStone (CYP3A4 substrate) with CYP3A4 inhibitors, such as hormonal contraceptives may increase miFEPRIStone exposure. Use concomitantly only when necessary, carefully weighing the potential benefit versus the potential risk, and limit the dose of miFEPRIStone to 900 mg per day. Also, consider using the lowest hormonal contraceptives dose necessary, and monitor and follow up appropriately. Based on the long terminal half-life of miFEPRIStone after reaching steady state, elapse at least 2 weeks after cessation of miFEPRIStone before initiating hormonal contraceptives. MiFEPRIStone is a strong CYP3A4 inhibitor, so use extreme caution when miFEPRIStone is coadministered with drugs that have high first pass metabolism via CYP3A4, such as hormonal contraceptives. Prefer alternative drugs without these metabolic characteristics when possible1.
Why it happens (mechanism)
Inhibition of CYP3A4-mediated metabolism of miFEPRIStone; inhibition of CYP3A4-mediated metabolism by miFEPRIStone; pharmacologic antagonism
Literature reports
2 reports — tap to read
a) In a drug interaction study, coadministration of miFEPRIStone 1200 mg once daily for 10 days and simvastatin (CYP3A4 substrate) 80 mg single dose, resulted in increased simvastatin AUC and Cmax by 10.40-fold and 7.02-fold, respectively. Also resulted in increased simvastatin acid AUC and Cmax by 15.7-fold and 18.20, respectively 1.
b) In a drug interaction study, coadministration of miFEPRIStone, 600 mg once daily for 17 days and ketoconazole (CYP3A inhibitor), 200 mg bid on days 13 to 17 resulted in increased miFEPRIStone AUC and Cmax by 1.38-fold and 1.28-fold, respectively 1.
Common questions
Can I take Estradiol and Mifepristone together?
Reduced hormonal contraceptive exposure, an increased miFEPRIStone exposure and an increased hormonal contraceptives exposure Always confirm with your pharmacist or prescriber before making any change.
How serious is the Estradiol and Mifepristone interaction?
It is rated major. Potentially serious — often needs a change or close monitoring.
How quickly could this interaction happen?
The documented onset is "unspecified". The timing of this interaction is not well characterized.
How strong is the evidence for this interaction?
The evidence is graded "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Estradiol or Mifepristone need adjusting while I take them together?
- What symptoms should prompt me to call you or my prescriber right away?
- Does the timing of my doses matter for this combination?
- Is there a safer alternative to one of these medications for me?
References (1)
- Product Information: KORLYM(R) oral tablets, mifepristone oral tablets. Corcept Therapeutics Incorporated (per Dailmed), Redwood City, CA, 2024. DailyMed
Keep reading about Mifepristone
Keep reading about Estradiol
These medications also interact with supplements
Prescription drugs aren't the whole picture — herbal and dietary supplements can interact with them too. From the evidence-graded Natural Medicines database:
major · moderate · minor — check everything you take with our drug–supplement interaction checker.
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