Drug Interaction Report

Mifepristone and Erdafitinib: Interaction Details

A pharmacist-reviewed analysis of the Mifepristone and Erdafitinib interaction: the documented clinical effects, severity rating, onset, mechanism, and management considerations, with cited references throughout.

AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature

Mifepristone

Korlym Mifeprex
+

Erdafitinib

Balversa Balversa®
Dr. Brian Staiger, PharmD, BCPS
Medically reviewed by
Dr. Brian Staiger, PharmD, BCPS
Updated Aug 8, 2026
Editorial policy · Data sources
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Interaction severity
Major
Potentially serious — often needs a change or close monitoring.
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.

Of 225 documented Mifepristone interactions, 139 are rated major — including this one.
Worried about symptoms right now? Contact your pharmacist or prescriber, or call Poison Control at 1-800-222-1222 (US). Call 911 for an emergency.
Onset
unspecified
Evidence
theoretical
Severity
Major

What happens

Increased erdafitinib exposure and an increased miFEPRIStone exposure

Interaction Deep Dive

Coadministration of erdafitinib (a CYP2C9 and CYP3A4 substrate) with miFEPRIStone (a strong CYP3A4 inhibitor and a moderate CYP2C9 inhibitor) may lead to increased erdafitinib plasma concentrations, increasing the risk for erdafitinib-related toxicity. Consider alternative therapies that are not moderate CYP2C9 inhibitors or strong CYP3A4 inhibitors during treatment with erdafitinib. If concomitant use is unavoidable, closely monitor for adverse events and consider dose modifications accordingly. If miFEPRIStone is discontinued, the erdafitinib dose may be increased in the absence of drug-related toxicity. Erdafitinib mean ratios for Cmax and AUC(inf) were increased 121% and 148%, respectively, when coadministered with fluconazole (a moderate CYP2C9 and CYP3A4 inhibitor) compared with erdafitinib alone1. Additionally, concomitant use of miFEPRIStone (CYP3A4 substrate) with erdafitinib (CYP3A4 inhibitor) may increase miFEPRIStone exposure. Carefully weigh the benefit of concomitant use of these agents against the potential risks. Limit the dose of miFEPRIStone to 900 mg. Wait at least 2 weeks after stopping miFEPRIStone before initiating erdafitinib 2.

Why it happens (mechanism)

Inhibition of CYP2C9-mediated erdafitinib metabolism; inhibition of CYP3A4-mediated erdafitinib metabolism; inhibition of CYP3A4-mediated metabolism of miFEPRIStone

Literature reports

3 reports — tap to read

a) Erdafitinib mean ratios for Cmax and AUC(inf) were increased 121% and 148%, respectively, when coadministered with fluconazole (a moderate CYP2C9 and CYP3A4 inhibitor) compared with erdafitinib alone 1.

b) In a pharmacokinetic study, the concomitant administration of a single oral dose of ALPRAZolam 1 mg in healthy subjects receiving miFEPRIStone 1200 mg once daily for 10 days resulted in increased ALPRAZolam (CYP3A4 inhibitor) exposure. Compared with ALPRAZolam administration alone, coadministration with miFEPRIStone resulted in an AUC and Cmax geometric mean ratio of 1.8 and 0.81, respectively for ALPRAZolam, and 0.76 and 0.39, respectively for the 4-hydroxy-ALPRAZolam metabolite 2.

c) Erdafitinib mean ratios for Cmax and AUC(inf) were increased 105% and 134%, respectively, when coadministered with itraconazole (a strong CYP3A4 inhibitor and P-gp inhibitor) compared with erdafitinib alone 1.

Common questions

Can I take Mifepristone and Erdafitinib together?

Increased erdafitinib exposure and an increased miFEPRIStone exposure Always confirm with your pharmacist or prescriber before making any change.

How serious is the Mifepristone and Erdafitinib 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.

Questions for your pharmacist

  • Does my dose of Mifepristone or Erdafitinib 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 (2)

  1. Product Information: BALVERSA(R) oral tablets, erdafitinib oral tablets. Janssen Products LP (per FDA), Horsham, PA, 2024. DailyMed
  2. Product Information: KORLYM(R) oral tablets, mifepristone oral tablets. Corcept Therapeutics Incorporated (per Dailmed), Redwood City, CA, 2024. DailyMed
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Mifepristone

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Erdafitinib

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Beyond drug–drug

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:

Mifepristone + Activated Charcoal American Hellebore Arsenic Cesium Ephedra Grapefruit Sida Cordifolia St. John's Wort + 143 more
Erdafitinib + Activated Charcoal Grapefruit Phosphate Salts St. John's Wort Acacia Rigidula Adrafinil African Wild Potato Alkanna + 161 more

major · moderate · minor — check everything you take with our drug–supplement interaction checker.

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This information is for education, not a substitute for professional medical advice. Do not start, stop, or change any medication without talking to your pharmacist or prescriber.