Drug interactions
Erythromycin + Thioridazine
Severity: Contraindicated
Erythromycin and Thioridazine: contraindicated 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
Both drugs prolong the QT interval, and erythromycin also inhibits the metabolism of thioridazine. The combination can raise the risk of torsades de pointes and sudden cardiac death. Thioridazine is already restricted because of its cardiac toxicity.
What this interaction means in plain words
Erythromycin 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.
Erythromycin belongs to Anti Bacterial; Thioridazine belongs to Central Nervous System.
Why it happens
Additive QT prolongation plus erythromycin inhibition of CYP3A4 and possibly other pathways, raising thioridazine exposure.
What to do
Avoid the combination and choose a non-QT-prolonging antibiotic such as a beta-lactam or doxycycline where appropriate. If unavoidable, obtain a baseline ECG and correct potassium and magnesium.
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?
Pro+ members
Unlock the full page
Create an account and start a Pro+ trial to unlock the full management advice for Erythromycin and Thioridazine, 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.
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 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 with Thioridazine?
MediHelp rates the interaction as contraindicated. Erythromycin 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 erythromycin also inhibits the metabolism of thioridazine. The combination can raise the risk of torsades de pointes and sudden cardiac death. Thioridazine is already restricted because of its cardiac toxicity.
How serious is the interaction between Erythromycin 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 beta-lactam or doxycycline where appropriate. If unavoidable, obtain a baseline ECG and correct potassium and magnesium.
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.
