Drug interactions
Ketoconazole + Venlafaxine
Severity: Major
Ketoconazole and Venlafaxine: major 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 increases venlafaxine exposure and both drugs are associated with QT prolongation. The combination may raise the risk of arrhythmia, especially with other risk factors, and may increase serotonergic or hypertensive adverse effects.
What this interaction means in plain words
Ketoconazole and Venlafaxine can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for.
Ketoconazole belongs to Anti Fungals; Venlafaxine belongs to Central Nervous System.
Why it happens
Ketoconazole inhibits CYP3A4 (a minor venlafaxine pathway) and both drugs have additive QT-prolonging effects.
What to do
Obtain a baseline ECG and correct potassium and magnesium before combining; monitor QTc during therapy. Avoid in patients with long QT or other QT-prolonging drugs, and consider an alternative antifungal.
What to ask your pharmacist
- Does the benefit of taking both outweigh the risk in my case?
- Do I need any blood test, ECG or other check while on both?
- What early warning signs should I watch for, and what should I do if they appear?
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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 Venlafaxine
- Isocarboxazid + Venlafaxine Contraindicated
- Methylene blue + Venlafaxine Contraindicated
- Phenelzine + Venlafaxine Contraindicated
- Procarbazine + Venlafaxine Contraindicated
- Rasagiline + Venlafaxine Contraindicated
- Safinamide + Venlafaxine Contraindicated
Frequently asked questions
Can I take Ketoconazole with Venlafaxine?
MediHelp rates the interaction as major. Ketoconazole and Venlafaxine can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for. Ketoconazole increases venlafaxine exposure and both drugs are associated with QT prolongation. The combination may raise the risk of arrhythmia, especially with other risk factors, and may increase serotonergic or hypertensive adverse effects.
How serious is the interaction between Ketoconazole and Venlafaxine?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Obtain a baseline ECG and correct potassium and magnesium before combining; monitor QTc during therapy. Avoid in patients with long QT or other QT-prolonging drugs, and consider an alternative antifungal.
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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