Drug interactions
Fluconazole + Sulfamethoxazole
Severity: Moderate
Fluconazole and Sulfamethoxazole: 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
Both drugs have been associated with QT prolongation, and fluconazole also inhibits CYP2C9, which metabolizes sulfamethoxazole. Concomitant use may increase arrhythmia risk and sulfamethoxazole exposure.
What this interaction means in plain words
Fluconazole and Sulfamethoxazole 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.
Why it happens
Additive QTc effects and fluconazole inhibition of CYP2C9-mediated sulfamethoxazole metabolism.
What to do
Monitor ECG in patients with other QT risk factors and keep potassium and magnesium normal. Watch for sulfonamide adverse effects.
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
Frequently asked questions
Can I take Fluconazole with Sulfamethoxazole?
MediHelp rates the interaction as moderate. Fluconazole and Sulfamethoxazole 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. Both drugs have been associated with QT prolongation, and fluconazole also inhibits CYP2C9, which metabolizes sulfamethoxazole. Concomitant use may increase arrhythmia risk and sulfamethoxazole exposure.
How serious is the interaction between Fluconazole and Sulfamethoxazole?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor ECG in patients with other QT risk factors and keep potassium and magnesium normal. Watch for sulfonamide adverse effects.
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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