Just like many other medications, ondansetron can prolong the QTc interval on an electrocardiogram. In fact, the FDA released a Drug Safety Communication in 2012 recommending against IV doses > 16 mg to help limit the risk. A prospective, observational study in 40 cardiac patients (heart failure or ACS) found that ondansetron 4 mg IV prolonged the QTc interval by 19 msec for up to 2 hours after the dose (Hafermann, Drug Healthc Patient Safety 2011). A retrospective cohort study of 210 ondansetron doses in pediatric ICU patients found that the QTC interval increased to 460-500 msec in 29% and to more than 500 msec in 11% (Trivedi, Pediatr Crit Care Med 2016). Underlying electrolyte abnormalities and organ dysfunction seemed to add the most risk.
But, what about in ED patients? What is the extent of QTC prolongation and is it clinically significant? Two groups have now published on this patient population. Here’s what they found.