Drug interactions
Erythromycin + Fosamprenavir
Severity: Major
Erythromycin and Fosamprenavir: 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
Fosamprenavir (amprenavir) inhibits CYP3A4 and can raise erythromycin levels, and erythromycin may raise amprenavir concentrations. This increases the risk of adverse effects including QT prolongation.
What this interaction means in plain words
Erythromycin and Fosamprenavir 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
Mutual CYP3A4 inhibition raising exposure to both drugs.
What to do
Consider azithromycin or another alternative. If coadministered, monitor ECG and for toxicity of both drugs.
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
- Erythromycin 250 mg Gastro-resistant Tablets - SmPC sections 4.3/4.5 (class statement: Protease inhibitors; "Protease inhibitors: in concomitant administration of erythromycin and protease inhibitors, an inhibition of the decomposition of erythromycin has been observed") — electronic medicines compendium (UK SmPC)
Other interactions of Erythromycin
- Conivaptan + Erythromycin Contraindicated
- Dihydroergotamine intranasal + Erythromycin Contraindicated
- Dihydroergotamine + Erythromycin Contraindicated
- Domperidone + Erythromycin Contraindicated
- Dronedarone + Erythromycin Contraindicated
- Droperidol + Erythromycin Contraindicated
Frequently asked questions
Can I take Erythromycin with Fosamprenavir?
MediHelp rates the interaction as major. Erythromycin and Fosamprenavir 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. Fosamprenavir (amprenavir) inhibits CYP3A4 and can raise erythromycin levels, and erythromycin may raise amprenavir concentrations. This increases the risk of adverse effects including QT prolongation.
How serious is the interaction between Erythromycin and Fosamprenavir?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Consider azithromycin or another alternative. If coadministered, monitor ECG and for toxicity of both drugs.
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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