Drug interactions
Flecainide + Lumefantrine
Severity: Major
Flecainide and Lumefantrine: 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
Lumefantrine can inhibit CYP2D6, the main enzyme clearing flecainide, so flecainide exposure may rise. Because flecainide has a narrow therapeutic index, higher levels raise the risk of conduction slowing and proarrhythmia. Lumefantrine itself also prolongs the QT interval.
What this interaction means in plain words
Flecainide and Lumefantrine 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.
Why it happens
Lumefantrine inhibits CYP2D6-mediated flecainide metabolism, and both drugs have additive effects on cardiac conduction and repolarization.
What to do
Avoid the combination if possible and consider an alternative antimalarial. If it is unavoidable, monitor ECG (QRS and QTc) and consider flecainide plasma levels and dose reduction.
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
Frequently asked questions
Can I take Flecainide with Lumefantrine?
MediHelp rates the interaction as major. Flecainide and Lumefantrine 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. Lumefantrine can inhibit CYP2D6, the main enzyme clearing flecainide, so flecainide exposure may rise. Because flecainide has a narrow therapeutic index, higher levels raise the risk of conduction slowing and proarrhythmia. Lumefantrine itself also prolongs the QT interval.
How serious is the interaction between Flecainide and Lumefantrine?
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 the combination if possible and consider an alternative antimalarial. If it is unavoidable, monitor ECG (QRS and QTc) and consider flecainide plasma levels and dose reduction.
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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