Drug interactions
Olanzapine + Thioridazine
Severity: Major
Olanzapine and Thioridazine: 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
Both antipsychotics can prolong the QTc interval, though thioridazine has by far the stronger effect. The combination adds to the risk of torsades de pointes and sudden cardiac death. Thioridazine is reserved for refractory cases because of this liability and is typically contraindicated with other QT-prolonging agents.
What this interaction means in plain words
Olanzapine and Thioridazine 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.
Olanzapine belongs to Central Nervous System; Thioridazine belongs to Central Nervous System.
Why it happens
Additive blockade of cardiac hERG potassium channels causing delayed ventricular repolarization.
What to do
Avoid combining antipsychotics where possible; prefer monotherapy. If both are used, monitor ECG and correct potassium and magnesium.
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 Thioridazine
- Abiraterone + Thioridazine Contraindicated
- Adagrasib + Thioridazine Contraindicated
- Amiodarone + Thioridazine Contraindicated
- Amisulpride + Thioridazine Contraindicated
- Amitriptyline + Thioridazine Contraindicated
- Amoxapine + Thioridazine Contraindicated
Other interactions of Olanzapine
Frequently asked questions
Can I take Olanzapine with Thioridazine?
MediHelp rates the interaction as major. Olanzapine and Thioridazine 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. Both antipsychotics can prolong the QTc interval, though thioridazine has by far the stronger effect. The combination adds to the risk of torsades de pointes and sudden cardiac death. Thioridazine is reserved for refractory cases because of this liability and is typically contraindicated with other QT-prolonging agents.
How serious is the interaction between Olanzapine and Thioridazine?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid combining antipsychotics where possible; prefer monotherapy. If both are used, monitor ECG and correct potassium and magnesium.
What other medicines interact with Thioridazine?
MediHelp also lists interactions of Thioridazine with, for example, Abiraterone, Adagrasib, Amiodarone. The full list is on the Thioridazine page.
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