Drug interactions
Arsenic trioxide + Ondansetron
Severity: Major
Arsenic trioxide and Ondansetron: 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
Arsenic trioxide causes QT prolongation and torsades de pointes, and its labeling advises against other QT-prolonging drugs. Ondansetron adds to this effect and, given the antiemetic need in oncology, the combination is a real risk.
What this interaction means in plain words
Arsenic trioxide 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.
Arsenic trioxide belongs to Oncology; Ondansetron belongs to Gastrointestinal Tract.
Why it happens
Additive prolongation of cardiac repolarization.
What to do
Avoid where possible and choose an antiemetic with minimal QT effect. If used, maintain potassium and magnesium and monitor ECG closely.
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 Arsenic trioxide
- Amiodarone + Arsenic trioxide Contraindicated
- Amisulpride + Arsenic trioxide Contraindicated
- Arsenic trioxide + Clomipramine Contraindicated
- Arsenic trioxide + Dronedarone Contraindicated
- Arsenic trioxide + Fluphenazine Contraindicated
- Arsenic trioxide + Gemifloxacin Contraindicated
Frequently asked questions
Can I take Arsenic trioxide with Ondansetron?
MediHelp rates the interaction as major. Arsenic trioxide 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. Arsenic trioxide causes QT prolongation and torsades de pointes, and its labeling advises against other QT-prolonging drugs. Ondansetron adds to this effect and, given the antiemetic need in oncology, the combination is a real risk.
How serious is the interaction between Arsenic trioxide 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: Avoid where possible and choose an antiemetic with minimal QT effect. If used, maintain potassium and magnesium and monitor ECG closely.
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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