Drug interactions
Flecainide + Thioridazine
Severity: Contraindicated
Flecainide 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
Thioridazine markedly prolongs the QT interval, and inhibits CYP2D6, which can raise flecainide levels. The combination carries a high risk of torsades de pointes and sudden cardiac death.
What this interaction means in plain words
Flecainide 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.
Flecainide belongs to Cardiovascular; Thioridazine belongs to Central Nervous System.
Why it happens
Additive QT prolongation and conduction effects plus CYP2D6 inhibition by thioridazine reducing flecainide clearance.
What to do
Do not use together; choose a different antipsychotic with lower QT liability. If a patient is already on both, stop one under cardiac monitoring.
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 Flecainide
- Flecainide + Nirmatrelvir Contraindicated
- Flecainide + Nirmatrelvir / ritonavir Contraindicated
- Flecainide + Pimozide Contraindicated
- Flecainide + Ritonavir Contraindicated
- Flecainide + Tipranavir Contraindicated
- Flecainide + Vandetanib 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 Flecainide with Thioridazine?
MediHelp rates the interaction as contraindicated. Flecainide 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. Thioridazine markedly prolongs the QT interval, and inhibits CYP2D6, which can raise flecainide levels. The combination carries a high risk of torsades de pointes and sudden cardiac death.
How serious is the interaction between Flecainide 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 use together; choose a different antipsychotic with lower QT liability. If a patient is already on both, stop one under cardiac monitoring.
What other medicines interact with Flecainide?
MediHelp also lists interactions of Flecainide with, for example, Nirmatrelvir, Nirmatrelvir / ritonavir, Pimozide. The full list is on the Flecainide page.
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