Losartan and Fluconazole: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Fluconazole
Losartan
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 conversion of losartan to its active metabolite (E-3174)
Interaction Deep Dive
Consider monitoring of blood pressure continuously when losartan is administered concomitantly with fluconazole. Fluconazole inhibits the metabolism of losartan to its active metabolite (E-3174) which is responsible for most of the angiotensin II-receptor antagonism which occurs during treatment with losartan1. Fluconazole is a potent inhibitor of the cytochrome P450 2C9 (CYP2C9) hepatic isoenzyme. In vitro studies have determined that CYP2C9 and CYP3A4 are involved in the metabolism of losartan to an active carboxylic acid metabolite, E-3174. E-3174 is 10 to 40 times more potent than losartan and is responsible for most of the angiotensin II receptor antagonism that occurs with losartan therapy. In one study involving 32 subjects, fluconazole was shown to significantly inhibit the conversion of losartan to E-3174. Conversely, coadministered fluconazole did not affect the steady-state pharmacokinetics of eprosartan, which is not metabolized through the cytochrome P450 hepatic system 2.
Why it happens (mechanism)
Inhibition of CYP2C9-mediated losartan metabolism by fluconazole
Literature reports
1 report — tap to read
a) In one study, 16 healthy male subjects received eprosartan (300 mg twice daily) and another 16 subjects received losartan (100 mg once daily) on study days 1 to 20. Fluconazole 200 mg daily was given to all 32 subjects on day 11 and continued through day 20. No significant drug interactions were observed between fluconazole and eprosartan. However, fluconazole increased the losartan area under the concentration-time curve (AUC) and maximum concentration (Cmax) by 66% and 30%, respectively. Fluconazole also decreased the AUC and Cmax of E-3174 (the active metabolite of losartan) by 43% and 56%, respectively 2.
Common questions
Can I take Losartan and Fluconazole together?
Reduced conversion of losartan to its active metabolite (E-3174) Always confirm with your pharmacist or prescriber before making any change.
How serious is the Losartan 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 "probable". Good supporting evidence, though not definitively proven.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Losartan 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: DIFLUCAN(R) oral tablets, suspension, fluconazole oral tablets, suspension. Roerig (per FDA), New York, NY, 2023. DailyMed
- Kazierad DJ, Martin DE, Blum RA, et al: Effect of fluconazole on the pharmacokinetics of eprosartan and losartan in healthy male volunteers. Clin Pharmacol Ther 1997; 62:417-425. PubMed
Keep reading about Fluconazole
Keep reading about Losartan
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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