Fluoxetine and Arsenic Trioxide: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Jul 11, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Fluoxetine
Arsenic 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 interval prolongation, torsades de pointes, cardiac arrest)
Interaction Deep Dive
Arsenic trioxide and FLUoxetine have been shown to prolong the QTc interval at the recommended therapeutic dose12. Even though no formal drug interaction studies have been done, arsenic trioxide should not be administered with other drugs which are also known or have the potential to prolong the QTc interval, including FLUoxetine 1. Consider ECG assessment and periodic ECG monitoring if initiating treatment with FLUoxetine in patients with risk factors for QT interval prolongation and ventricular arrhythmia. Discontinue FLUoxetine and obtain a cardiac evaluation if patients develop signs or symptoms consistent with ventricular arrhythmia 2.
Why it happens (mechanism)
Additive QT interval prolongation
Literature reports
2 reports — tap to read
a) QT/QTc prolongation should be expected during treatment with arsenic trioxide and torsade de pointes as well as complete heart block has been reported. Over 460 ECG tracings from 40 patients with refractory or relapsed APL treated with arsenic trioxide were evaluated for QTc prolongation. Sixteen of 40 patients (40%) had at least one ECG tracing with a QTc interval greater than 500 msec. Prolongation of the QTc was observed between 1 and 5 weeks after arsenic trioxide infusion, and then returned towards baseline by the end of 8 weeks after arsenic trioxide infusion. In these ECG evaluations, women did not experience more pronounced QT prolongation than men, and there was no correlation with age 1.
b) QT Prolongation was observed on the electrocardiogram (ECG) of a 52- year-old man who had been taking FLUoxetine (20 milligrams/day for 2 weeks, followed by 40 milligrams/day thereafter) for depression for 3 months. An ECG just before the start of FLUoxetine treatment showed a normal QT interval. The QT interval returned to normal within 10 days of discontinuing FLUoxetine treatment 3.
Common questions
Can I take Fluoxetine and Arsenic Trioxide together?
An increased risk of cardiotoxicity (QT interval prolongation, torsades de pointes, cardiac arrest) Always confirm with your pharmacist or prescriber before making any change.
How serious is the Fluoxetine 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 Fluoxetine 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 (3)
- Product Information: TRISENOX(R) intravenous injection, arsenic trioxide intravenous injection. Teva Pharmaceuticals USA Inc (per FDA), Parsippany, nj, 2020. DailyMed
- Product Information: PROZAC(R) oral capsules, fluoxetine oral capsules. Lilly USA LLC (per FDA), Indianapolis, IN, 2023. DailyMed
- Varriale P: Fluoxetine (Prozac) as a cause of QT prolongation (Letter). Arch Intern Med 2001; 161:612. PubMed
Keep reading about Fluoxetine
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.
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