Drug interactions
Flecainide + Nirmatrelvir / ritonavir
Severity: Contraindicated
Flecainide and Nirmatrelvir / ritonavir: 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
Ritonavir strongly inhibits CYP3A4 and CYP2D6, major routes of flecainide metabolism. Flecainide concentrations can rise, causing proarrhythmia, QRS widening and conduction disturbances. Labeling lists flecainide as contraindicated.
What this interaction means in plain words
Flecainide and Nirmatrelvir / ritonavir 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
Ritonavir inhibits CYP2D6 and CYP3A4, reducing flecainide clearance.
What to do
Avoid; use an alternative antiviral such as remdesivir. If treatment cannot be changed, specialist-guided flecainide management with ECG monitoring is needed.
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 + Pimozide Contraindicated
- Flecainide + Ritonavir Contraindicated
- Flecainide + Thioridazine Contraindicated
- Flecainide + Tipranavir Contraindicated
- Flecainide + Vandetanib Contraindicated
Frequently asked questions
Can I take Flecainide with Nirmatrelvir / ritonavir?
MediHelp rates the interaction as contraindicated. Flecainide and Nirmatrelvir / ritonavir 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. Ritonavir strongly inhibits CYP3A4 and CYP2D6, major routes of flecainide metabolism. Flecainide concentrations can rise, causing proarrhythmia, QRS widening and conduction disturbances. Labeling lists flecainide as contraindicated.
How serious is the interaction between Flecainide and Nirmatrelvir / ritonavir?
MediHelp rates it contraindicated, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid; use an alternative antiviral such as remdesivir. If treatment cannot be changed, specialist-guided flecainide management with ECG monitoring is needed.
What other medicines interact with Flecainide?
MediHelp also lists interactions of Flecainide with, for example, Nirmatrelvir, Pimozide, Ritonavir. The full list is on the Flecainide page.
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