Drug interactions
Flecainide + Trimethoprim
Severity: Moderate
Flecainide and Trimethoprim: moderate 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
Trimethoprim has been linked to QT prolongation and hyperkalemia, both of which may heighten flecainide's proarrhythmic risk. Trimethoprim may also reduce renal tubular secretion of some cationic drugs, possibly raising flecainide levels.
What this interaction means in plain words
Flecainide and Trimethoprim can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Flecainide belongs to Cardiovascular; Trimethoprim belongs to Anti Bacterial.
Why it happens
Additive effects on cardiac conduction and repolarization, with possible reduced renal tubular secretion of flecainide.
What to do
Monitor ECG and serum potassium during co-therapy, particularly in renal impairment. Consider an alternative antibiotic if conduction intervals lengthen.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
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Other interactions of Flecainide
- Flecainide + Nirmatrelvir Contraindicated
- Flecainide + Nirmatrelvir / ritonavir Contraindicated
- Flecainide + Pimozide Contraindicated
- Flecainide + Ritonavir Contraindicated
- Flecainide + Thioridazine Contraindicated
- Flecainide + Tipranavir Contraindicated
Other interactions of Trimethoprim
Frequently asked questions
Can I take Flecainide with Trimethoprim?
MediHelp rates the interaction as moderate. Flecainide and Trimethoprim can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. Trimethoprim has been linked to QT prolongation and hyperkalemia, both of which may heighten flecainide's proarrhythmic risk. Trimethoprim may also reduce renal tubular secretion of some cationic drugs, possibly raising flecainide levels.
How serious is the interaction between Flecainide and Trimethoprim?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor ECG and serum potassium during co-therapy, particularly in renal impairment. Consider an alternative antibiotic if conduction intervals lengthen.
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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