Drug interactions
Ondansetron + Pimozide
Severity: Major
Ondansetron and Pimozide: major 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
Pimozide markedly prolongs the QT interval and has been associated with torsades de pointes. Adding ondansetron, which also lengthens QT, increases that risk and the combination is best avoided.
What this interaction means in plain words
Ondansetron and Pimozide 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.
Ondansetron belongs to Gastrointestinal Tract; Pimozide belongs to Central Nervous System.
Why it happens
Additive hERG potassium channel blockade causing delayed ventricular repolarization.
What to do
Avoid the combination and choose an antiemetic with less QT effect. If it cannot be avoided, correct electrolytes and monitor the ECG.
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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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 Pimozide
- Adagrasib + Pimozide Contraindicated
- Amiodarone + Pimozide Contraindicated
- Amisulpride + Pimozide Contraindicated
- Amitriptyline + Pimozide Contraindicated
- Amoxapine + Pimozide Contraindicated
- Anagrelide + Pimozide Contraindicated
Frequently asked questions
Can I take Ondansetron with Pimozide?
MediHelp rates the interaction as major. Ondansetron and Pimozide 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. Pimozide markedly prolongs the QT interval and has been associated with torsades de pointes. Adding ondansetron, which also lengthens QT, increases that risk and the combination is best avoided.
How serious is the interaction between Ondansetron and Pimozide?
MediHelp rates it major, 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 an antiemetic with less QT effect. If it cannot be avoided, correct electrolytes and monitor the ECG.
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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