Drug interactions
Flecainide + Nirmatrelvir
Severity: Contraindicated
Flecainide and Nirmatrelvir: 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
Flecainide has a narrow therapeutic index, and nirmatrelvir given with ritonavir inhibits CYP3A4 and CYP2D6. Raised flecainide levels can cause conduction block, ventricular arrhythmias and heart failure worsening. Nirmatrelvir is only given with ritonavir clinically.
What this interaction means in plain words
Flecainide and Nirmatrelvir 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; Nirmatrelvir belongs to Anti Virals.
Why it happens
Ritonavir-boosted inhibition of CYP2D6 and CYP3A4 reduces flecainide clearance.
What to do
Do not co-administer; select an alternative COVID-19 therapy. If unavoidable, hold flecainide with ECG monitoring under specialist guidance.
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 / ritonavir Contraindicated
- Flecainide + Pimozide Contraindicated
- Flecainide + Ritonavir Contraindicated
- Flecainide + Thioridazine Contraindicated
- Flecainide + Tipranavir Contraindicated
- Flecainide + Vandetanib Contraindicated
Other interactions of Nirmatrelvir
- Alfuzosin + Nirmatrelvir Contraindicated
- Amiodarone + Nirmatrelvir Contraindicated
- Apalutamide + Nirmatrelvir Contraindicated
- Carbamazepine + Nirmatrelvir Contraindicated
- Colchicine + Nirmatrelvir Contraindicated
- Dronedarone + Nirmatrelvir Contraindicated
Frequently asked questions
Can I take Flecainide with Nirmatrelvir?
MediHelp rates the interaction as contraindicated. Flecainide and Nirmatrelvir 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 has a narrow therapeutic index, and nirmatrelvir given with ritonavir inhibits CYP3A4 and CYP2D6. Raised flecainide levels can cause conduction block, ventricular arrhythmias and heart failure worsening. Nirmatrelvir is only given with ritonavir clinically.
How serious is the interaction between Flecainide and Nirmatrelvir?
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 co-administer; select an alternative COVID-19 therapy. If unavoidable, hold flecainide with ECG monitoring under specialist guidance.
What other medicines interact with Flecainide?
MediHelp also lists interactions of Flecainide with, for example, Nirmatrelvir / ritonavir, Pimozide, Ritonavir. The full list is on the Flecainide page.
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