Drug interactions
Fluconazole + Tamoxifen
Severity: Moderate
Fluconazole and Tamoxifen: moderate interaction.
Last updated
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Tamoxifen is converted to active metabolites such as endoxifen mainly by CYP2D6 and CYP3A4, with contributions from CYP2C9. Fluconazole may alter this activation and could reduce efficacy, and both drugs may prolong QT.
What this interaction means in plain words
Fluconazole and Tamoxifen can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Fluconazole belongs to Anti Fungals; Tamoxifen belongs to Endocrine.
Why it happens
Fluconazole inhibits CYP2C9 and CYP3A4, potentially altering tamoxifen metabolite formation; additive QT effects are also possible.
What to do
Consider alternative antifungal therapy for prolonged courses. Monitor ECG if there are QT risk factors and review clinical response to tamoxifen.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
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Other interactions of Fluconazole
- Dihydroergotamine intranasal + Fluconazole Contraindicated
- Dihydroergotamine + Fluconazole Contraindicated
- Dofetilide + Fluconazole Contraindicated
- Domperidone + Fluconazole Contraindicated
- Dronedarone + Fluconazole Contraindicated
- Erythromycin + Fluconazole Contraindicated
Other interactions of Tamoxifen
- Amiodarone + Tamoxifen Major
- Anastrozole + Tamoxifen Major
- Bupropion + Tamoxifen Major
- Carbamazepine + Tamoxifen Major
- Cinacalcet + Tamoxifen Major
- Dacomitinib + Tamoxifen Major
Frequently asked questions
Can I take Fluconazole with Tamoxifen?
MediHelp rates the interaction as moderate. Fluconazole and Tamoxifen can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. Tamoxifen is converted to active metabolites such as endoxifen mainly by CYP2D6 and CYP3A4, with contributions from CYP2C9. Fluconazole may alter this activation and could reduce efficacy, and both drugs may prolong QT.
How serious is the interaction between Fluconazole and Tamoxifen?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Consider alternative antifungal therapy for prolonged courses. Monitor ECG if there are QT risk factors and review clinical response to tamoxifen.
What other medicines interact with Fluconazole?
MediHelp also lists interactions of Fluconazole with, for example, Dihydroergotamine intranasal, Dihydroergotamine, Dofetilide. The full list is on the Fluconazole page.
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