Drug interactions
Flecainide + Terbinafine
Severity: Major
Flecainide and Terbinafine: major 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 is cleared largely by CYP2D6 and has a narrow therapeutic index, so terbinafine can raise its levels. Elevated flecainide may cause QRS widening, conduction block and proarrhythmia.
What this interaction means in plain words
Flecainide and Terbinafine 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; Terbinafine belongs to Anti Fungals.
Why it happens
CYP2D6 inhibition by terbinafine reduces flecainide metabolism.
What to do
Monitor ECG (PR and QRS duration) and flecainide plasma levels, and reduce the dose if needed; consider an alternative antifungal if feasible.
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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Other interactions of Terbinafine
- Terbinafine + Thioridazine Contraindicated
- Desipramine + Terbinafine Major
- Eliglustat + Terbinafine Major
- Imipramine + Terbinafine Major
- Maprotiline + Terbinafine Major
- Metoclopramide intranasal + Terbinafine 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 Terbinafine?
MediHelp rates the interaction as major. Flecainide and Terbinafine 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 is cleared largely by CYP2D6 and has a narrow therapeutic index, so terbinafine can raise its levels. Elevated flecainide may cause QRS widening, conduction block and proarrhythmia.
How serious is the interaction between Flecainide and Terbinafine?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor ECG (PR and QRS duration) and flecainide plasma levels, and reduce the dose if needed; consider an alternative antifungal if feasible.
What other medicines interact with Terbinafine?
MediHelp also lists interactions of Terbinafine with, for example, Thioridazine, Desipramine, Eliglustat. The full list is on the Terbinafine page.
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