Drug interactions
Erythromycin + Ritonavir
Severity: Major
Erythromycin and Ritonavir: 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
Ritonavir is a potent CYP3A4 inhibitor and can markedly raise erythromycin concentrations, while erythromycin can also raise ritonavir levels. Both can prolong the QT interval, so the risk of torsades de pointes and other toxicity is increased.
What this interaction means in plain words
Erythromycin and Ritonavir 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; Ritonavir belongs to Anti Virals.
Why it happens
Mutual CYP3A4 inhibition and P-glycoprotein effects with additive QT prolongation.
What to do
Avoid if possible; consider azithromycin or a non-macrolide alternative. If combined, monitor ECG and electrolytes and consider reducing the erythromycin dose, especially in renal impairment.
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 Ritonavir
- Alfuzosin + Ritonavir Contraindicated
- Amiodarone + Ritonavir Contraindicated
- Avanafil + Ritonavir Contraindicated
- Colchicine + Ritonavir Contraindicated
- Dronedarone + Ritonavir Contraindicated
- Eletriptan + Ritonavir Contraindicated
Frequently asked questions
Can I take Erythromycin with Ritonavir?
MediHelp rates the interaction as major. Erythromycin and Ritonavir 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. Ritonavir is a potent CYP3A4 inhibitor and can markedly raise erythromycin concentrations, while erythromycin can also raise ritonavir levels. Both can prolong the QT interval, so the risk of torsades de pointes and other toxicity is increased.
How serious is the interaction between Erythromycin and Ritonavir?
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 if possible; consider azithromycin or a non-macrolide alternative. If combined, monitor ECG and electrolytes and consider reducing the erythromycin dose, especially in renal impairment.
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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