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.