Arsenic Trioxide Injection and Promethazine: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Jul 11, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Promethazine
Arsenic Trioxide Injection
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 QT interval prolongation
Interaction Deep Dive
Arsenic trioxide is known to prolong the QT interval and may result in complete atrioventricular block and/or ventricular arrhythmias, including torsade de pointes. Although this interaction has not been evaluated, the concomitant use of arsenic trioxide with other drugs that may prolong the QT interval, such as promethazine, may increase the risk of prolonged QT interval and ventricular arrhythmias. When possible, promethazine therapy should be discontinued prior to arsenic trioxide treatment1; however, if coadministration is required, monitor for QT interval prolongation.
Why it happens (mechanism)
Additive effects on QT interval prolongation
Common questions
Can I take Arsenic Trioxide Injection and Promethazine together?
An increased risk of QT interval prolongation Always confirm with your pharmacist or prescriber before making any change.
How serious is the Arsenic Trioxide Injection and Promethazine 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 Arsenic Trioxide Injection or Promethazine 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 (1)
- Product Information: Trisenox(R) IV injection, arsenic trioxide IV injection. Cephalon, Inc (per FDA), Frazer, PA, 2010.
Keep reading about Promethazine
Keep reading about Arsenic Trioxide Injection
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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.
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