Drug interactions
Azithromycin + Ondansetron
Severity: Major
Azithromycin and Ondansetron: major interaction.
Last updated Sources: UK SmPC
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 prolong the QT interval, and using them together may increase the risk of torsades de pointes. The risk is greater with congenital long QT syndrome, electrolyte disturbances, heart failure or bradycardia.
What this interaction means in plain words
Azithromycin and Ondansetron 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.
Azithromycin belongs to Anti Bacterial; Ondansetron belongs to Gastrointestinal Tract.
Why it happens
Additive blockade of cardiac repolarizing potassium currents leading to QT prolongation.
What to do
Prefer a non-QT-prolonging alternative where possible; otherwise obtain a baseline ECG and correct potassium and magnesium before use. Avoid in congenital long QT syndrome.
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
- Ondansetron 4 mg film-coated tablets - SmPC sections 4.3/4.5 (class statement: antibiotics; "antibiotics (such as erythromycin)") — electronic medicines compendium (UK SmPC)
Other interactions of Ondansetron
- Apomorphine + Ondansetron Contraindicated
- Ondansetron + Thioridazine Contraindicated
- Ondansetron + Vandetanib Contraindicated
- Adagrasib + Ondansetron Major
- Amiodarone + Ondansetron Major
- Amisulpride + Ondansetron Major
Other interactions of Azithromycin
- Azithromycin + Cisapride Contraindicated
- Azithromycin + Domperidone Contraindicated
- Azithromycin + Dronedarone Contraindicated
- Azithromycin + Pimozide Contraindicated
- Azithromycin + Piperaquine Contraindicated
- Azithromycin + Thioridazine Contraindicated
Frequently asked questions
Can I take Azithromycin with Ondansetron?
MediHelp rates the interaction as major. Azithromycin and Ondansetron 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 prolong the QT interval, and using them together may increase the risk of torsades de pointes. The risk is greater with congenital long QT syndrome, electrolyte disturbances, heart failure or bradycardia.
How serious is the interaction between Azithromycin and Ondansetron?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Prefer a non-QT-prolonging alternative where possible; otherwise obtain a baseline ECG and correct potassium and magnesium before use. Avoid in congenital long QT syndrome.
What other medicines interact with Ondansetron?
MediHelp also lists interactions of Ondansetron with, for example, Apomorphine, Thioridazine, Vandetanib. The full list is on the Ondansetron page.
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