Erlotinib and Fluconazole: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Fluconazole
Erlotinib
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
Increased erlotinib exposure
Interaction Deep Dive
Use caution when administering erlotinib (a CYP3A4 substrate) together with fluconazole (a moderate CYP3A4 inhibitor) as concomitant use may result in elevated erlotinib plasma concentrations2. While this interaction has not been specifically studied, concurrent use of erlotinib and ketoconazole (a potent CYP3A4 inhibitor) resulted in an 67% increase in erlotinib AUC.1. Fluconazole-mediated enzyme inhibition may persist for 4 to 5 days after discontinuation. If concomitant use is required, carefully monitor for erlotinib-associated adverse effects 2. Dosage adjustments of erlotinib may be required 1.
Why it happens (mechanism)
Inhibition of CYP3A4-mediated erlotinib metabolism by fluconazole
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 Erlotinib and Fluconazole together?
Increased erlotinib exposure Always confirm with your pharmacist or prescriber before making any change.
How serious is the Erlotinib and Fluconazole 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.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Erlotinib or Fluconazole 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)
- Product Information: TARCEVA(R) oral tablets, erlotinib oral tablets. OSI Pharmaceuticals, LLC (per FDA), Northbrook, IL, 2014. DailyMed
- Product Information: DIFLUCAN(R) oral tablets, oral suspension, intravenous infusion injection, fluconazole oral tablets, oral suspension, intravenous infusion injection. Roerig (per FDA), New York, NY, 2014. DailyMed
Keep reading about Fluconazole
Keep reading about Erlotinib
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.
Check another combination
Our instant two-drug interaction checker is almost here.
Still have questions about this combination?
Every question gets a real answer from a licensed pharmacist — free, and usually within a day.
Ask the pharmacist