Drug interactions
Erythromycin ethylsuccinate + Foscarnet
Severity: Major
Erythromycin ethylsuccinate and Foscarnet: major interaction.
Last updated Sources: US FDA label
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
Erythromycin is a recognized QT-prolonging macrolide, and foscarnet can also lengthen the QT interval and lower electrolytes. The combination increases the chance of torsades de pointes, especially with other risk factors.
What this interaction means in plain words
Erythromycin ethylsuccinate and Foscarnet 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.
Why it happens
Additive QT prolongation with foscarnet-related electrolyte disturbances.
What to do
Prefer a non-QT-prolonging antibiotic. If the combination is needed, check ECG and correct potassium, magnesium and calcium.
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
Other interactions of Foscarnet
- Cidofovir + Foscarnet Contraindicated
- Foscarnet + Pimozide Contraindicated
- Foscarnet + Thioridazine Contraindicated
- Foscarnet + Vandetanib Contraindicated
- Adagrasib + Foscarnet Major
- Adefovir + Foscarnet Major
Frequently asked questions
Can I take Erythromycin ethylsuccinate with Foscarnet?
MediHelp rates the interaction as major. Erythromycin ethylsuccinate and Foscarnet 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. Erythromycin is a recognized QT-prolonging macrolide, and foscarnet can also lengthen the QT interval and lower electrolytes. The combination increases the chance of torsades de pointes, especially with other risk factors.
How serious is the interaction between Erythromycin ethylsuccinate and Foscarnet?
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 antibiotic. If the combination is needed, check ECG and correct potassium, magnesium and calcium.
What other medicines interact with Foscarnet?
MediHelp also lists interactions of Foscarnet with, for example, Cidofovir, Pimozide, Thioridazine. The full list is on the Foscarnet page.
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