Drug interactions
Erythromycin + Posaconazole
Severity: Major
Erythromycin and Posaconazole: 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
Posaconazole can increase erythromycin concentrations, and both agents prolong the QT interval. The combination increases the risk of torsades de pointes and sudden cardiac events.
What this interaction means in plain words
Erythromycin and Posaconazole 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 belongs to Anti Bacterial; Posaconazole belongs to Anti Fungals.
Why it happens
Posaconazole inhibits CYP3A4 (and P-gp), reducing erythromycin clearance, and both drugs have additive QT-prolonging effects.
What to do
Avoid the combination where possible and choose a non-QT-prolonging antibiotic. If both are essential, monitor ECG and keep potassium and magnesium within normal range.
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 Erythromycin
- Conivaptan + Erythromycin Contraindicated
- Dihydroergotamine intranasal + Erythromycin Contraindicated
- Dihydroergotamine + Erythromycin Contraindicated
- Domperidone + Erythromycin Contraindicated
- Dronedarone + Erythromycin Contraindicated
- Droperidol + Erythromycin Contraindicated
Other interactions of Posaconazole
- Artemether + Posaconazole Contraindicated
- Avanafil + Posaconazole Contraindicated
- Cobimetinib + Posaconazole Contraindicated
- Conivaptan + Posaconazole Contraindicated
- Dihydroergotamine intranasal + Posaconazole Contraindicated
- Dihydroergotamine + Posaconazole Contraindicated
Frequently asked questions
Can I take Erythromycin with Posaconazole?
MediHelp rates the interaction as major. Erythromycin and Posaconazole 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. Posaconazole can increase erythromycin concentrations, and both agents prolong the QT interval. The combination increases the risk of torsades de pointes and sudden cardiac events.
How serious is the interaction between Erythromycin and Posaconazole?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid the combination where possible and choose a non-QT-prolonging antibiotic. If both are essential, monitor ECG and keep potassium and magnesium within normal range.
What other medicines interact with Erythromycin?
MediHelp also lists interactions of Erythromycin with, for example, Conivaptan, Dihydroergotamine intranasal, Dihydroergotamine. The full list is on the Erythromycin page.
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