Drug interactions
Quinidine + Trimethoprim
Severity: Moderate
Quinidine 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
Both drugs have been associated with QT prolongation, so the combination may add to arrhythmia risk. Trimethoprim can also cause hyperkalemia, which may modify cardiac conduction effects.
What this interaction means in plain words
Quinidine 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.
Quinidine belongs to Anti Parasitic; Trimethoprim belongs to Anti Bacterial.
Why it happens
Additive effects on cardiac repolarization, with possible trimethoprim-induced hyperkalemia.
What to do
Monitor the ECG and serum potassium. Consider an alternative antibiotic in patients with other QT risk factors.
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 Quinidine
- Adagrasib + Quinidine Contraindicated
- Arsenic trioxide + Quinidine Contraindicated
- Artemether / lumefantrine + Quinidine Contraindicated
- Chloroquine + Quinidine Contraindicated
- Dofetilide + Quinidine Contraindicated
- Dronedarone + Quinidine Contraindicated
Other interactions of Trimethoprim
Frequently asked questions
Can I take Quinidine with Trimethoprim?
MediHelp rates the interaction as moderate. Quinidine 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. Both drugs have been associated with QT prolongation, so the combination may add to arrhythmia risk. Trimethoprim can also cause hyperkalemia, which may modify cardiac conduction effects.
How serious is the interaction between Quinidine 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 the ECG and serum potassium. Consider an alternative antibiotic in patients with other QT risk factors.
What other medicines interact with Quinidine?
MediHelp also lists interactions of Quinidine with, for example, Adagrasib, Arsenic trioxide, Artemether / lumefantrine. The full list is on the Quinidine page.
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