Ondansetron and Arsenic Trioxide: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Jul 11, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Ondansetron
No brand names on recordArsenic Trioxide
How we grade severity & evidence
Severity levels
- Contraindicated: These should generally not be used together.
- Major: Potentially serious — often needs a change or close monitoring.
- Moderate: Can be significant — usually manageable with monitoring.
- Minor: Usually limited clinical impact.
Evidence grades
- Established: Well documented — supported by controlled studies or strong clinical data.
- Probable: Good supporting evidence, though not definitively proven.
- Suspected: Some evidence suggests this interaction, but it is not well established.
- Possible: Limited or conflicting evidence; the interaction may occur.
- Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.
Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.
What happens
An increased risk of cardiotoxicity (QT prolongation, torsades de pointes, cardiac arrest)
Interaction Deep Dive
During treatment with arsenic trioxide, QT/QTc prolongation should be expected and torsade de point as well as complete heart block has been reported1. Rarely, and predominantly with the intravenous formulation, transient ECG changes including QT interval prolongation have occurred with ondansetron 2. Use caution when ondansetron is coadministered with agents that prolong the QT interval, including arsenic trioxide.
Why it happens (mechanism)
Additive effects on QT prolongation
Common questions
Can I take Ondansetron and Arsenic Trioxide together?
An increased risk of cardiotoxicity (QT prolongation, torsades de pointes, cardiac arrest) Always confirm with your pharmacist or prescriber before making any change.
How serious is the Ondansetron and Arsenic Trioxide interaction?
It is rated major. Potentially serious — often needs a change or close monitoring.
How quickly could this interaction happen?
The documented onset is "unspecified". The timing of this interaction is not well characterized.
How strong is the evidence for this interaction?
The evidence is graded "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Ondansetron or Arsenic Trioxide need adjusting while I take them together?
- What symptoms should prompt me to call you or my prescriber right away?
- Does the timing of my doses matter for this combination?
- Is there a safer alternative to one of these medications for me?
References (2)
- Product Information: TRISENOX(R) injection, arsenic trioxide injection. Cephalon Inc. Frazer, PA, 2005. DailyMed
- Product Information: ZOFRAN(R) oral tablets, oral solution, ZOFRAN ODT(R) orally disintegrating tablets, ondansetron hcl oral tablets, oral solution, orally disintegrating solution. GlaxoSmithKline, Research Triangle Park, NC, 2006.
Keep reading about Ondansetron
Keep reading about Arsenic Trioxide
These medications also interact with supplements
Prescription drugs aren't the whole picture — herbal and dietary supplements can interact with them too. From the evidence-graded Natural Medicines database:
major · moderate · minor — check everything you take with our drug–supplement interaction checker.
Check another combination
Our instant two-drug interaction checker is almost here.
Still have questions about this combination?
Every question gets a real answer from a licensed pharmacist — free, and usually within a day.
Ask the pharmacist