Drug interactions
Flecainide + Ondansetron
Severity: Major
Flecainide and Ondansetron: major interaction.
Last updated Sources: UK SmPC
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
Flecainide slows cardiac conduction and can be proarrhythmic, and ondansetron adds QT-prolonging potential. The combination may increase the risk of serious ventricular arrhythmias, particularly in structural heart disease.
What this interaction means in plain words
Flecainide and Ondansetron 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.
Flecainide belongs to Cardiovascular; Ondansetron belongs to Gastrointestinal Tract.
Why it happens
Additive effects on cardiac conduction and repolarization (sodium channel blockade with QT prolongation).
What to do
Avoid if possible and choose an antiemetic with less cardiac effect. If combined, monitor the ECG and electrolytes.
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
- Ondansetron 4 mg film-coated tablets - SmPC sections 4.3/4.5 (class statement: antiarrhythmics; "antiarrhythmics (such as amiodarone)") — electronic medicines compendium (UK SmPC)
Other interactions of Ondansetron
- Apomorphine + Ondansetron Contraindicated
- Ondansetron + Thioridazine Contraindicated
- Ondansetron + Vandetanib Contraindicated
- Adagrasib + Ondansetron Major
- Amiodarone + Ondansetron Major
- Amisulpride + Ondansetron Major
Other interactions of Flecainide
- Flecainide + Nirmatrelvir Contraindicated
- Flecainide + Nirmatrelvir / ritonavir Contraindicated
- Flecainide + Pimozide Contraindicated
- Flecainide + Ritonavir Contraindicated
- Flecainide + Thioridazine Contraindicated
- Flecainide + Tipranavir Contraindicated
Frequently asked questions
Can I take Flecainide with Ondansetron?
MediHelp rates the interaction as major. Flecainide and Ondansetron 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. Flecainide slows cardiac conduction and can be proarrhythmic, and ondansetron adds QT-prolonging potential. The combination may increase the risk of serious ventricular arrhythmias, particularly in structural heart disease.
How serious is the interaction between Flecainide and Ondansetron?
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 antiemetic with less cardiac effect. If combined, monitor the ECG and electrolytes.
What other medicines interact with Ondansetron?
MediHelp also lists interactions of Ondansetron with, for example, Apomorphine, Thioridazine, Vandetanib. The full list is on the Ondansetron page.
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