Ondansetron and Alfuzosin: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Ondansetron
No brand names on recordAlfuzosin
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
Both alfuzosin and ondansetron may prolong the QT interval12 and concomitant use of these agents may increase the risk of serious cardiac events, including ventricular arrhythmias and/or torsade de pointes. If coadministration is required, ECG monitoring is recommended 2.
Why it happens (mechanism)
Additive effects on QT interval prolongation
Literature reports
1 report — tap to read
a) In a postmarketing study that evaluated the effect of concomitant administration of alfuzosin with another QT interval-prolonging drug of similar effect size, the observed QT interval prolongation was greater than that seen with either drug alone, but was not more than additive. The corrected (Fridericia) QT interval (QTcF) increased by 5.9 milliseconds (upper bound of 95% confidence interval (CI), 9.4 milliseconds). The QTcF increase observed with moxifloxacin 400 mg (positive control) was 10.2 milliseconds (upper bound 95% CI, 13.8 milliseconds). The mean placebo-subtracted QTcF increase following administration of alfuzosin 10 mg alone was 1.9 milliseconds (upper bound 95% CI, 5.5 milliseconds) 3.
Common questions
Can I take Ondansetron and Alfuzosin together?
An increased risk of QT interval prolongation Always confirm with your pharmacist or prescriber before making any change.
How serious is the Ondansetron and Alfuzosin 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 Alfuzosin 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: UROXATRAL(R) oral extended-release tablets, alfuzosin HCl oral extended-release tablets. Sanofi-Aventis U.S. LLC, Bridgewater, NJ, 2010. DailyMed
- Product Information: ZOFRAN ODT(R) oral disintegrating tablets, ondansetron oral disintegrating tablets. GlaxoSmithKline (per FDA), Research Triangle Park, NC, 2011. DailyMed
- Product Information: UROXATRAL(R) extended-release oral tablets, alfuzosin HCL extended-release oral tablets. Sanofi-aventis, Bridgewater, NJ, 2010. DailyMed
Keep reading about Ondansetron
Keep reading about Alfuzosin
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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