Drug interactions
Levofloxacin + Trimethoprim
Severity: Moderate
Levofloxacin 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
Levofloxacin prolongs the QT interval, and trimethoprim has been occasionally associated with QT prolongation and arrhythmia. The combination might add to arrhythmic risk, especially with hypokalemia, hyperkalemia from trimethoprim, or cardiac disease.
What this interaction means in plain words
Levofloxacin 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.
Levofloxacin belongs to Anti Bacterial; Trimethoprim belongs to Anti Bacterial.
Why it happens
Possible additive QT prolongation; the effect of trimethoprim is not well established.
What to do
Check an ECG in patients with additional QT risk factors and keep potassium and magnesium within normal range. Choose an alternative agent if QTc is already prolonged.
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 Levofloxacin
- Dronedarone + Levofloxacin Contraindicated
- Ibutilide + Levofloxacin Contraindicated
- Levofloxacin + Thioridazine Contraindicated
- Levofloxacin + Vandetanib Contraindicated
- Levofloxacin + Ziprasidone Contraindicated
- Adagrasib + Levofloxacin Major
Other interactions of Trimethoprim
Frequently asked questions
Can I take Levofloxacin with Trimethoprim?
MediHelp rates the interaction as moderate. Levofloxacin 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. Levofloxacin prolongs the QT interval, and trimethoprim has been occasionally associated with QT prolongation and arrhythmia. The combination might add to arrhythmic risk, especially with hypokalemia, hyperkalemia from trimethoprim, or cardiac disease.
How serious is the interaction between Levofloxacin 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: Check an ECG in patients with additional QT risk factors and keep potassium and magnesium within normal range. Choose an alternative agent if QTc is already prolonged.
What other medicines interact with Levofloxacin?
MediHelp also lists interactions of Levofloxacin with, for example, Dronedarone, Ibutilide, Thioridazine. The full list is on the Levofloxacin page.
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