Drug interactions
Erythromycin stearate + Thioridazine
Severity: Contraindicated
Erythromycin stearate and Thioridazine: 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 combining them raises the risk of torsades de pointes and sudden cardiac death. Erythromycin also inhibits CYP3A4 and may raise thioridazine exposure, further adding to the risk.
What this interaction means in plain words
Erythromycin stearate and Thioridazine 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 blockade of cardiac potassium channels (hERG) causing QT prolongation, with possible erythromycin-mediated metabolic inhibition of thioridazine.
What to do
Avoid the combination and choose a non-QT-prolonging antibiotic such as a non-macrolide alternative. If unavoidable, obtain a baseline ECG, correct potassium and magnesium, and monitor QTc closely.
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 Thioridazine
- Abiraterone + Thioridazine Contraindicated
- Adagrasib + Thioridazine Contraindicated
- Amiodarone + Thioridazine Contraindicated
- Amisulpride + Thioridazine Contraindicated
- Amitriptyline + Thioridazine Contraindicated
- Amoxapine + Thioridazine Contraindicated
Frequently asked questions
Can I take Erythromycin stearate with Thioridazine?
MediHelp rates the interaction as contraindicated. Erythromycin stearate and Thioridazine 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 combining them raises the risk of torsades de pointes and sudden cardiac death. Erythromycin also inhibits CYP3A4 and may raise thioridazine exposure, further adding to the risk.
How serious is the interaction between Erythromycin stearate and Thioridazine?
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 and choose a non-QT-prolonging antibiotic such as a non-macrolide alternative. If unavoidable, obtain a baseline ECG, correct potassium and magnesium, and monitor QTc closely.
What other medicines interact with Thioridazine?
MediHelp also lists interactions of Thioridazine with, for example, Abiraterone, Adagrasib, Amiodarone. The full list is on the Thioridazine page.
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