MajorClass III antiarrhythmics (Vaughan Williams)×5-HT3 serotonin receptor antagonist
Updated · Methodology
Mechanism
Ondansetron prolongs QT 10-15 ms, amiodarone 30-50 ms. Additive torsades risk.
Symptoms
QTc above 500 ms, syncope, torsades de pointes risk.
Management
Alternative – metoclopramide. If ondansetron needed – single IV dose no higher than 8 mg.
Check the full regimen, not just this pair
Opens the checker with these two drugs prefilled. Add the rest of the regimen and recompute additive risks.
Summary of a multi-drug list →
Medicine list: everything you take in one place →
Sources
- FDA: Zofran (ondansetron) prescribing information (2010)
- AEMPS: Ficha técnica: Ondansetrón (nº registro 72117), sección 4.5 (2025)– AEMPS, CIMA, nº registro 72117, revisión 02/2025, sección 4.5