Drug interactions
Erythromycin stearate + Perphenazine
Severity: Major
Erythromycin stearate 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 drugs can prolong the QT interval, and combining them raises the risk of torsades de pointes. Erythromycin also inhibits CYP3A4 and may modestly raise perphenazine exposure.
What this interaction means in plain words
Erythromycin stearate 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.
Why it happens
Additive blockade of cardiac IKr potassium channels, with possible CYP3A4 inhibition by erythromycin.
What to do
Choose a non-QT-prolonging antibiotic where possible. 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?
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References
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 stearate with Perphenazine?
MediHelp rates the interaction as major. Erythromycin stearate 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 drugs can prolong the QT interval, and combining them raises the risk of torsades de pointes. Erythromycin also inhibits CYP3A4 and may modestly raise perphenazine exposure.
How serious is the interaction between Erythromycin stearate 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: Choose a non-QT-prolonging antibiotic where possible. If unavoidable, obtain a baseline ECG, correct potassium and magnesium, and monitor the QTc.
What other medicines interact with Perphenazine?
MediHelp also lists interactions of Perphenazine with, for example, Ibutilide, Pimozide, Thioridazine. The full list is on the Perphenazine page.
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