Drug interactions
Fluconazole + Phenobarbital
Severity: Moderate
Fluconazole and Phenobarbital: 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
Phenobarbital is an enzyme inducer and can lower fluconazole exposure, while fluconazole inhibits CYP2C19 and CYP2C9, which contribute to phenobarbital clearance and may raise its levels. The result may be reduced antifungal effect or increased sedation.
What this interaction means in plain words
Fluconazole and Phenobarbital 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
Phenobarbital induces hepatic enzymes, and fluconazole inhibits CYP2C19 and CYP2C9.
What to do
Monitor for antifungal failure and for sedation or toxicity; check phenobarbital serum levels when fluconazole is started or stopped.
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 Phenobarbital?
MediHelp rates the interaction as moderate. Fluconazole and Phenobarbital 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. Phenobarbital is an enzyme inducer and can lower fluconazole exposure, while fluconazole inhibits CYP2C19 and CYP2C9, which contribute to phenobarbital clearance and may raise its levels. The result may be reduced antifungal effect or increased sedation.
How serious is the interaction between Fluconazole and Phenobarbital?
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 for antifungal failure and for sedation or toxicity; check phenobarbital serum levels when fluconazole is started or stopped.
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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