Drug interactions
Clozapine + Flecainide
Severity: Major
Clozapine and Flecainide: major 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
Clozapine can prolong the QT interval and cause myocarditis and tachycardia, while flecainide slows cardiac conduction and can be proarrhythmic. The combination increases the risk of serious ventricular arrhythmias. Flecainide is also generally avoided in structural heart disease.
What this interaction means in plain words
Clozapine and Flecainide 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.
Clozapine belongs to Central Nervous System; Flecainide belongs to Cardiovascular.
Why it happens
Additive effects on cardiac conduction and repolarization.
What to do
Avoid if possible and choose an alternative antiarrhythmic or antipsychotic. If co-use is required, monitor ECG and electrolytes closely and consider plasma flecainide levels.
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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References
Other interactions of Flecainide
- Flecainide + Nirmatrelvir Contraindicated
- Flecainide + Nirmatrelvir / ritonavir Contraindicated
- Flecainide + Pimozide Contraindicated
- Flecainide + Ritonavir Contraindicated
- Flecainide + Thioridazine Contraindicated
- Flecainide + Tipranavir Contraindicated
Other interactions of Clozapine
- Clozapine + Deferiprone Contraindicated
- Clozapine + Irinotecan Contraindicated
- Clozapine + Pimozide Contraindicated
- Clozapine + Thioridazine Contraindicated
- Acalabrutinib + Clozapine Major
- Adagrasib + Clozapine Major
Frequently asked questions
Can I take Clozapine with Flecainide?
MediHelp rates the interaction as major. Clozapine and Flecainide 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. Clozapine can prolong the QT interval and cause myocarditis and tachycardia, while flecainide slows cardiac conduction and can be proarrhythmic. The combination increases the risk of serious ventricular arrhythmias. Flecainide is also generally avoided in structural heart disease.
How serious is the interaction between Clozapine and Flecainide?
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 if possible and choose an alternative antiarrhythmic or antipsychotic. If co-use is required, monitor ECG and electrolytes closely and consider plasma flecainide levels.
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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