Drug interactions
Ketoconazole + Tolbutamide
Severity: Moderate
Ketoconazole 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
Ketoconazole can increase tolbutamide concentrations and prolong its half-life, raising the risk of hypoglycemia. The effect is most relevant with systemic ketoconazole therapy.
What this interaction means in plain words
Ketoconazole 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.
Ketoconazole belongs to Anti Fungals; Tolbutamide belongs to Endocrine.
Why it happens
Ketoconazole inhibits CYP2C9-mediated metabolism of tolbutamide.
What to do
Check blood glucose frequently during co-therapy and after stopping ketoconazole. Lower the tolbutamide dose if hypoglycemia occurs or consider an alternative antidiabetic.
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 Ketoconazole
- Alfuzosin + Ketoconazole Contraindicated
- Alprazolam + Ketoconazole Contraindicated
- Avanafil + Ketoconazole Contraindicated
- Conivaptan + Ketoconazole Contraindicated
- Dihydroergotamine intranasal + Ketoconazole Contraindicated
- Dihydroergotamine + Ketoconazole 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 Ketoconazole with Tolbutamide?
MediHelp rates the interaction as moderate. Ketoconazole 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. Ketoconazole can increase tolbutamide concentrations and prolong its half-life, raising the risk of hypoglycemia. The effect is most relevant with systemic ketoconazole therapy.
How serious is the interaction between Ketoconazole 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: Check blood glucose frequently during co-therapy and after stopping ketoconazole. Lower the tolbutamide dose if hypoglycemia occurs or consider an alternative antidiabetic.
What other medicines interact with Ketoconazole?
MediHelp also lists interactions of Ketoconazole with, for example, Alfuzosin, Alprazolam, Avanafil. The full list is on the Ketoconazole page.
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