Drug interactions
Diltiazem + Ketoconazole
Severity: Moderate
Diltiazem and Ketoconazole: 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 are CYP3A4 substrates and inhibitors, so concentrations of each may rise. Higher diltiazem exposure can cause bradycardia, AV block and hypotension, and ketoconazole levels may also increase.
What this interaction means in plain words
Diltiazem and Ketoconazole 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.
Diltiazem belongs to Cardiovascular; Ketoconazole belongs to Anti Fungals.
Why it happens
Mutual inhibition of CYP3A4-mediated metabolism, with additive negative inotropic and chronotropic effects.
What to do
Monitor heart rate, blood pressure and ECG, and reduce the diltiazem dose if bradycardia or hypotension occurs. Watch for ketoconazole adverse effects including hepatotoxicity.
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 Diltiazem
- Diltiazem + Flibanserin Contraindicated
- Diltiazem + Ivabradine Contraindicated
- Diltiazem + Lomitapide Contraindicated
- Diltiazem + Lonafarnib Contraindicated
- Acebutolol + Diltiazem Major
- Alfentanil + Diltiazem Major
Frequently asked questions
Can I take Diltiazem with Ketoconazole?
MediHelp rates the interaction as moderate. Diltiazem and Ketoconazole 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 are CYP3A4 substrates and inhibitors, so concentrations of each may rise. Higher diltiazem exposure can cause bradycardia, AV block and hypotension, and ketoconazole levels may also increase.
How serious is the interaction between Diltiazem and Ketoconazole?
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 heart rate, blood pressure and ECG, and reduce the diltiazem dose if bradycardia or hypotension occurs. Watch for ketoconazole adverse effects including hepatotoxicity.
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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