Drug interactions
Erythromycin + Promethazine
Severity: Moderate
Erythromycin and Promethazine: 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
Erythromycin and promethazine can each prolong the QT interval, so combined use may increase the risk of torsades de pointes. The concern is greatest in patients with structural heart disease, bradycardia or electrolyte imbalance.
What this interaction means in plain words
Erythromycin and Promethazine 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; Promethazine belongs to Respiratory.
Why it happens
Additive QT prolongation through cardiac potassium channel blockade.
What to do
Avoid in patients with known QT prolongation or other risk factors and consider an alternative antiemetic or antihistamine. Otherwise correct electrolytes and monitor the ECG.
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 Promethazine
- Cabergoline + Promethazine Contraindicated
- Dopamine + Promethazine Contraindicated
- Ibutilide + Promethazine Contraindicated
- Pimozide + Promethazine Contraindicated
- Promethazine + Thioridazine Contraindicated
- Alfentanil + Promethazine Major
Frequently asked questions
Can I take Erythromycin with Promethazine?
MediHelp rates the interaction as moderate. Erythromycin and Promethazine 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 and promethazine can each prolong the QT interval, so combined use may increase the risk of torsades de pointes. The concern is greatest in patients with structural heart disease, bradycardia or electrolyte imbalance.
How serious is the interaction between Erythromycin and Promethazine?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid in patients with known QT prolongation or other risk factors and consider an alternative antiemetic or antihistamine. Otherwise correct electrolytes and monitor the ECG.
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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