Drug interactions
Clozapine + Ondansetron
Severity: Major
Clozapine and Ondansetron: major interaction.
Last updated Sources: UK SmPC
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 lengthen the QT interval, so their combination may increase the risk of ventricular arrhythmia. Clozapine also carries risks of myocarditis and cardiomyopathy, which add to cardiac vulnerability.
What this interaction means in plain words
Clozapine and Ondansetron 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.
Clozapine belongs to Central Nervous System; Ondansetron belongs to Gastrointestinal Tract.
Why it happens
Additive QT prolongation through effects on cardiac repolarization.
What to do
Obtain a baseline ECG and correct potassium and magnesium before combining. Consider an antiemetic with less QT effect and monitor the ECG if ondansetron is required.
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 Ondansetron
- Apomorphine + Ondansetron Contraindicated
- Ondansetron + Thioridazine Contraindicated
- Ondansetron + Vandetanib Contraindicated
- Adagrasib + Ondansetron Major
- Amiodarone + Ondansetron Major
- Amisulpride + Ondansetron Major
Other interactions of Clozapine
- Clozapine + Deferiprone Contraindicated
- Clozapine + Irinotecan Contraindicated
- Clozapine + Pimozide Contraindicated
- Clozapine + Thioridazine Contraindicated
- Acalabrutinib + Clozapine Major
- Adagrasib + Clozapine Major
Frequently asked questions
Can I take Clozapine with Ondansetron?
MediHelp rates the interaction as major. Clozapine and Ondansetron 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 lengthen the QT interval, so their combination may increase the risk of ventricular arrhythmia. Clozapine also carries risks of myocarditis and cardiomyopathy, which add to cardiac vulnerability.
How serious is the interaction between Clozapine and Ondansetron?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Obtain a baseline ECG and correct potassium and magnesium before combining. Consider an antiemetic with less QT effect and monitor the ECG if ondansetron is required.
What other medicines interact with Ondansetron?
MediHelp also lists interactions of Ondansetron with, for example, Apomorphine, Thioridazine, Vandetanib. The full list is on the Ondansetron page.
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