Drug interactions
Erythromycin + Saquinavir
Severity: Contraindicated
Erythromycin and Saquinavir: contraindicated 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
Both drugs prolong the QT interval, and each can raise the other's levels through CYP3A4 inhibition, increasing the risk of torsades de pointes. Saquinavir labeling advises against use with QT-prolonging CYP3A substrates.
What this interaction means in plain words
Erythromycin and Saquinavir are not normally used together. Taking them at the same time is expected to cause harm or make one of them unsafe, so a different medicine is usually chosen for one of the two.
Why it happens
Additive QT prolongation combined with mutual CYP3A4 inhibition raising exposure to both drugs.
What to do
Avoid the combination; use a non-macrolide antibiotic such as a different class. Obtain ECG monitoring if unavoidable.
What to ask your pharmacist
- Is there an alternative to one of these two medicines for me?
- If both are essential, who is monitoring me and how often?
- Which symptoms mean I should stop and seek help straight away?
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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
Frequently asked questions
Can I take Erythromycin with Saquinavir?
MediHelp rates the interaction as contraindicated. Erythromycin and Saquinavir are not normally used together. Taking them at the same time is expected to cause harm or make one of them unsafe, so a different medicine is usually chosen for one of the two. Both drugs prolong the QT interval, and each can raise the other's levels through CYP3A4 inhibition, increasing the risk of torsades de pointes. Saquinavir labeling advises against use with QT-prolonging CYP3A substrates.
How serious is the interaction between Erythromycin and Saquinavir?
MediHelp rates it contraindicated, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid the combination; use a non-macrolide antibiotic such as a different class. Obtain ECG monitoring if unavoidable.
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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