Drug Interaction Report

Mifepristone and Erlotinib: Interaction Details

A pharmacist-reviewed analysis of the Mifepristone and Erlotinib 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
+

Erlotinib

Tarceva Tarceva®
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
Moderate
Can be significant — usually manageable with 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, 17 are rated moderate — including this one.
Onset
unspecified
Evidence
theoretical
Severity
Moderate

What happens

Increased erlotinib exposure

Interaction Deep Dive

Using erlotinib (a CYP3A4 substrate) together with mifepristone (a moderate CYP3A4 inhibitor) may result in elevated plasma concentrations of erlotinib increasing the risk for adverse effects12. Alternative agents should be used whenever possible 2. While this interaction has not been specifically studied, concurrent use of erlotinib and ketoconazole (another potent CYP3A4 inhibitor) resulted in an 67% increase in erlotinib AUC 1. If concomitant use is clinically required, dose adjustments 12, reduced frequency of dosing, or treatment discontinuation may be required. Monitoring for toxicity is recommended 2.

Why it happens (mechanism)

Inhibition of CYP3A4-mediated erlotinib metabolism by mifepristone

Literature reports

1 report — tap to read

a) During drug interaction studies, coadministration of erlotinib and ketoconazole (a strong CYP3A4 inhibitor) resulted in a 67% increase in erlotinib AUC 1.

Common questions

Can I take Mifepristone and Erlotinib together?

Increased erlotinib exposure Always confirm with your pharmacist or prescriber before making any change.

How serious is the Mifepristone and Erlotinib interaction?

It is rated moderate. Can be significant — usually manageable with 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 Erlotinib 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 anything you'd monitor while I'm on both?

References (2)

  1. Product Information: TARCEVA(R) oral tablets, erlotinib oral tablets. OSI Pharmaceuticals, LLC (per FDA), Northbrook, IL, 2014. DailyMed
  2. Product Information: Korlym(TM) oral tablets, mifepristone oral tablets. Corcept Therapeutics (per manufacturer), Menlo Park, CA, 2012. DailyMed
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Mifepristone

Keep reading about Mifepristone

All Mifepristone interactions (225)
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Erlotinib

Keep reading about Erlotinib

All Erlotinib interactions (83) Erlotinib drug information
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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
Erlotinib + Activated Charcoal Bilberry Coffee Charcoal European Mandrake Glucomannan Guar Gum Gum Arabic Slippery Elm + 10 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.