Drug interactions
Flecainide + Methadone
Severity: Major
Flecainide and Methadone: 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
Both drugs can affect cardiac conduction, and together they may increase the risk of ventricular arrhythmias including torsades de pointes. Methadone may also inhibit CYP2D6, which can raise flecainide levels.
What this interaction means in plain words
Flecainide and Methadone 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; Methadone belongs to Musculoskeletal.
Why it happens
Additive effects on cardiac conduction and QT interval, with possible CYP2D6 inhibition by methadone raising flecainide exposure.
What to do
Obtain a baseline ECG and monitor QRS and QTc after initiation or dose changes. Consider flecainide plasma level monitoring and an alternative antiarrhythmic in high-risk patients.
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 Methadone
- Alvimopan + Methadone Contraindicated
- Calcium / magnesium / potassium / sodium oxybates + Methadone Contraindicated
- Droperidol + Methadone Contraindicated
- Ibutilide + Methadone Contraindicated
- Isocarboxazid + Methadone Contraindicated
- Lefamulin + Methadone Contraindicated
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 Methadone?
MediHelp rates the interaction as major. Flecainide and Methadone 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. Both drugs can affect cardiac conduction, and together they may increase the risk of ventricular arrhythmias including torsades de pointes. Methadone may also inhibit CYP2D6, which can raise flecainide levels.
How serious is the interaction between Flecainide and Methadone?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Obtain a baseline ECG and monitor QRS and QTc after initiation or dose changes. Consider flecainide plasma level monitoring and an alternative antiarrhythmic in high-risk patients.
What other medicines interact with Methadone?
MediHelp also lists interactions of Methadone with, for example, Alvimopan, Calcium / magnesium / potassium / sodium oxybates, Droperidol. The full list is on the Methadone page.
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