Drug interactions
Fluconazole + Tolbutamide
Severity: Moderate
Fluconazole and Tolbutamide: 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
Fluconazole substantially reduces tolbutamide clearance and prolongs its half-life, increasing the risk of hypoglycemia. The effect is well documented for this CYP2C9 substrate.
What this interaction means in plain words
Fluconazole and Tolbutamide 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; Tolbutamide belongs to Endocrine.
Why it happens
Fluconazole inhibits CYP2C9, the main enzyme responsible for tolbutamide metabolism.
What to do
Monitor blood glucose frequently and lower the tolbutamide dose as needed during fluconazole therapy. Consider an alternative antidiabetic agent for prolonged azole courses.
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 Tolbutamide
- Glyburide-metformin + Tolbutamide Major
- Insulin degludec-liraglutide + Tolbutamide Major
- Aceclofenac + Tolbutamide Moderate
- Acemetacin + Tolbutamide Moderate
- Acetylsalicylic acid + Tolbutamide Moderate
- Albiglutide + Tolbutamide Moderate
Frequently asked questions
Can I take Fluconazole with Tolbutamide?
MediHelp rates the interaction as moderate. Fluconazole and Tolbutamide 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 substantially reduces tolbutamide clearance and prolongs its half-life, increasing the risk of hypoglycemia. The effect is well documented for this CYP2C9 substrate.
How serious is the interaction between Fluconazole and Tolbutamide?
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 blood glucose frequently and lower the tolbutamide dose as needed during fluconazole therapy. Consider an alternative antidiabetic agent for prolonged azole courses.
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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