Drug interactions
Procainamide + Thioridazine
Severity: Contraindicated
Procainamide and Thioridazine: contraindicated interaction.
Last updated Sources: US FDA label
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
Procainamide is a class IA antiarrhythmic that prolongs the QT interval, and thioridazine does so strongly. The combination markedly raises the risk of torsades de pointes.
What this interaction means in plain words
Procainamide 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.
Why it happens
Additive QT prolongation through potassium channel blockade.
What to do
Do not combine them. Use an alternative antiarrhythmic or antipsychotic without a QT effect.
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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References
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 Procainamide with Thioridazine?
MediHelp rates the interaction as contraindicated. Procainamide 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. Procainamide is a class IA antiarrhythmic that prolongs the QT interval, and thioridazine does so strongly. The combination markedly raises the risk of torsades de pointes.
How serious is the interaction between Procainamide 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 combine them. Use an alternative antiarrhythmic or antipsychotic without a QT effect.
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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