The incidence of torsades de pointes with peri‐operative low‐dose ondansetron administration

Study Objective The primary objective of this retrospective safety study was to determine the incidence of torsades de pointes (TdP) or death following perioperative administration of low‐dose, 4 mg, ondansetron for postoperative nausea and vomiting. Design and Setting This is a single‐center retrospective clinical trial. Patients The authors identified 32,737 patients who received 37,589 doses of ondansetron during a 2‐year time frame between March 2009 and February 2011 for surgical nausea prophylaxis or treatment of nausea. Measurements and Main Results Patients were cross‐matched with an electrocardiogram and adverse outcome database; this identified 4759 patients with documentation of a QTc >450 milliseconds (ms), all ventricular tachycardias including TdP within 48 hours of receiving ondansetron, or death within 7 days of receiving ondansetron. No patients developed TdP or died as a direct result of ondansetron administration (n = 0; event rate = 0.0 per 10,000, 95% CI 0.0 to 1.1 per 10,000). Forty‐six of 32,737 surgical patients had documented monomorphic ventricular tachycardia (VT) (n = 14; event rate = 4.3 per 10,000, 95% CI 2.3 to 7.2 per 10,000) or died (n = 32; event rate = 9.8 per 10,000, 95% CI 6.7 to 13.8 per 10,000) within 48 h of ondansetron administration. All monomorphic VT episodes were precipitated by existing cardiovascular disease; and 7 of 14 patients had documented monomorphic VT prior to receiving ondansetron. Of the 32 surgical patients who died, all deaths were precipitated by pre‐existing disease. Conclusion No episodes of TdP were identified in patients receiving ondansetron perioperatively. This suggests that low‐dose ondansetron does not contribute to the development of TdP.