Drug interactions
Ketoconazole + Thioridazine
Severity: Contraindicated
Ketoconazole and Thioridazine: contraindicated 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 can prolong the QT interval, and ketoconazole also raises thioridazine levels. The combination increases the risk of torsades de pointes and sudden cardiac death.
What this interaction means in plain words
Ketoconazole and Thioridazine are not normally used together. Taking them at the same time is expected to cause harm or make one of them unsafe, so a different medicine is usually chosen for one of the two.
Ketoconazole belongs to Anti Fungals; Thioridazine belongs to Central Nervous System.
Why it happens
Additive QT prolongation combined with CYP3A4 inhibition by ketoconazole that reduces thioridazine clearance.
What to do
Do not coadminister. Use a non-QT-prolonging antifungal or antipsychotic alternative.
What to ask your pharmacist
- Is there an alternative to one of these two medicines for me?
- If both are essential, who is monitoring me and how often?
- Which symptoms mean I should stop and seek help straight away?
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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 Thioridazine
- Abiraterone + Thioridazine Contraindicated
- Adagrasib + Thioridazine Contraindicated
- Amiodarone + Thioridazine Contraindicated
- Amisulpride + Thioridazine Contraindicated
- Amitriptyline + Thioridazine Contraindicated
- Amoxapine + Thioridazine Contraindicated
Frequently asked questions
Can I take Ketoconazole with Thioridazine?
MediHelp rates the interaction as contraindicated. Ketoconazole and Thioridazine are not normally used together. Taking them at the same time is expected to cause harm or make one of them unsafe, so a different medicine is usually chosen for one of the two. Both drugs can prolong the QT interval, and ketoconazole also raises thioridazine levels. The combination increases the risk of torsades de pointes and sudden cardiac death.
How serious is the interaction between Ketoconazole and Thioridazine?
MediHelp rates it contraindicated, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Do not coadminister. Use a non-QT-prolonging antifungal or antipsychotic alternative.
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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