Drug interactions
Erythromycin + Perphenazine
Severity: Major
Erythromycin and Perphenazine: major interaction.
Last updated Sources: Health Canada product monograph
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 erythromycin and perphenazine can prolong the QT interval, so using them together raises the risk of torsades de pointes and other serious ventricular arrhythmias. Risk is greater with electrolyte disturbance, cardiac disease or other QT-prolonging drugs.
What this interaction means in plain words
Erythromycin and Perphenazine 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; Perphenazine belongs to Central Nervous System.
Why it happens
Additive blockade of cardiac repolarizing potassium currents (hERG) causing QT prolongation; erythromycin may also modestly raise perphenazine exposure through CYP inhibition.
What to do
Prefer a non-macrolide antibiotic such as a non-QT-prolonging alternative. If unavoidable, obtain a baseline ECG, correct potassium and magnesium, and monitor the QTc.
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?
Pro+ members
Unlock the full page
Create an account and start a Pro+ trial to unlock the full management advice for Erythromycin and Perphenazine, the additional notes, the evidence detail and the whole-prescription interaction checker.
- Full clinical management advice
- Additional notes
- Evidence detail
- Interaction checker for a whole prescription
Try Pro+ free for 7 days on the web. No card needed.
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 Perphenazine
- Ibutilide + Perphenazine Contraindicated
- Perphenazine + Pimozide Contraindicated
- Perphenazine + Thioridazine Contraindicated
- Adagrasib + Perphenazine Major
- Alfentanil + Perphenazine Major
- Amiodarone + Perphenazine Major
Frequently asked questions
Can I take Erythromycin with Perphenazine?
MediHelp rates the interaction as major. Erythromycin and Perphenazine 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. Both erythromycin and perphenazine can prolong the QT interval, so using them together raises the risk of torsades de pointes and other serious ventricular arrhythmias. Risk is greater with electrolyte disturbance, cardiac disease or other QT-prolonging drugs.
How serious is the interaction between Erythromycin and Perphenazine?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Prefer a non-macrolide antibiotic such as a non-QT-prolonging alternative. If unavoidable, obtain a baseline ECG, correct potassium and magnesium, and monitor the QTc.
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.
Full monographs, dosing and an interaction checker in the MediHelp app
Open the complete reference, check multi-drug interactions and use dosing tools in the MediHelp app.
