Drug interactions
Erythromycin + Fostemsavir
Severity: Moderate
Erythromycin and Fostemsavir: moderate interaction.
Last updated
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, although fostemsavir only does so at supratherapeutic doses. Fostemsavir's inhibition of OATP1B1/3 might also modestly raise erythromycin levels.
What this interaction means in plain words
Erythromycin and Fostemsavir can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Erythromycin belongs to Anti Bacterial; Fostemsavir belongs to Anti Virals.
Why it happens
Additive QT prolongation with possible OATP1B1/3 inhibition by fostemsavir raising erythromycin exposure.
What to do
Use an ECG and electrolyte checks if the patient has other QT risk factors. Prefer a non-QT-prolonging antibiotic when feasible.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
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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 Fostemsavir
- Apalutamide + Fostemsavir Contraindicated
- Carbamazepine + Fostemsavir Contraindicated
- Enzalutamide + Fostemsavir Contraindicated
- Fostemsavir + Mitotane Contraindicated
- Fostemsavir + Phenytoin Contraindicated
- Fostemsavir + Rifampicin Contraindicated
Frequently asked questions
Can I take Erythromycin with Fostemsavir?
MediHelp rates the interaction as moderate. Erythromycin and Fostemsavir can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. Both drugs can prolong the QT interval, although fostemsavir only does so at supratherapeutic doses. Fostemsavir's inhibition of OATP1B1/3 might also modestly raise erythromycin levels.
How serious is the interaction between Erythromycin and Fostemsavir?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Use an ECG and electrolyte checks if the patient has other QT risk factors. Prefer a non-QT-prolonging antibiotic when feasible.
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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