Drug interactions
Quetiapine + Thioridazine
Severity: Major
Quetiapine 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 drugs can prolong the QT interval and cause sedation and dopamine blockade, so combining them raises the risk of torsades de pointes and extrapyramidal or neuroleptic malignant effects. Thioridazine is among the highest-risk antipsychotics for QT prolongation.
What this interaction means in plain words
Quetiapine 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.
Quetiapine belongs to Central Nervous System; Thioridazine belongs to Central Nervous System.
Why it happens
Additive QT prolongation, D2 antagonism and CNS depression.
What to do
Avoid combined use; if unavoidable, check baseline and follow-up ECGs, correct electrolytes and monitor for sedation and movement disorders.
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 Quetiapine
- Adagrasib + Quetiapine Major
- Amiodarone + Quetiapine Major
- Amisulpride + Quetiapine Major
- Amoxapine + Quetiapine Major
- Anagrelide + Quetiapine Major
- Apalutamide + Quetiapine Major
Frequently asked questions
Can I take Quetiapine with Thioridazine?
MediHelp rates the interaction as major. Quetiapine 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 drugs can prolong the QT interval and cause sedation and dopamine blockade, so combining them raises the risk of torsades de pointes and extrapyramidal or neuroleptic malignant effects. Thioridazine is among the highest-risk antipsychotics for QT prolongation.
How serious is the interaction between Quetiapine 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 combined use; if unavoidable, check baseline and follow-up ECGs, correct electrolytes and monitor for sedation and movement disorders.
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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