Drug interactions
Azithromycin + Furosemide
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.
Overview
Furosemide can cause hypokalemia and hypomagnesemia, which potentiate azithromycin-associated QT prolongation and increase the risk of torsades de pointes and other ventricular arrhythmias.
Mechanism of action
Pharmacodynamic: Azithromycin prolongs cardiac repolarization (QT). Furosemide may lower potassium and magnesium, sensitizing the myocardium to QT-prolonging effects. No meaningful pharmacokinetic interaction.
Clinical management
Assess and correct electrolytes before and during co-therapy; maintain K > 4 mEq/L and Mg > 2 mg/dL. Avoid additional QT-prolonging agents. Obtain ECG and consider alternative therapy if baseline QTc is prolonged, patient has history of torsades, structural heart disease, or symptomatic arrhythmias.
Drug reference
References
- Azithromycin (Zithromax) US Prescribing Information — Warnings: QT prolongation and torsades de pointes — FDA Label
- Furosemide (Lasix) US Prescribing Information — Warnings: fluid and electrolyte depletion (hypokalemia, hypomagnesemia) — FDA Label
- Azithromycin: Drug Interactions — Lexicomp
- Acquired long QT syndrome (drug-induced): Clinical manifestations, diagnosis, and management — UpToDate
- Azithromycin — Known Risk of Torsades de Pointes (QTDrugs Lists) — CredibleMeds
Frequently asked questions
Can I take Azithromycin with Furosemide?
The interaction is rated: Moderate. Furosemide can cause hypokalemia and hypomagnesemia, which potentiate azithromycin-associated QT prolongation and increase the risk of torsades de pointes and other ventricular arrhythmias.
How serious is the interaction between Azithromycin and Furosemide?
The interaction is rated: Moderate. Evidence level: Moderate.
How is the interaction between Azithromycin and Furosemide managed?
Assess and correct electrolytes before and during co-therapy; maintain K > 4 mEq/L and Mg > 2 mg/dL. Avoid additional QT-prolonging agents. Obtain ECG and consider alternative therapy if baseline QTc is prolonged, patient has history of torsades, structural heart disease, or symptomatic arrhythmias.
Why do Azithromycin and Furosemide interact?
Pharmacodynamic: Azithromycin prolongs cardiac repolarization (QT). Furosemide may lower potassium and magnesium, sensitizing the myocardium to QT-prolonging effects. No meaningful pharmacokinetic interaction.
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