The effect of intravenous ondansetron on QT interval in the emergency department

Objective

Ondansetron, a 5HT3 receptor antagonist, is commonly used in emergency departments to treat nausea and vomiting. In 2011, the Food and Drug Administration (FDA) issued a warning that this medicine may cause QT prolongation, potentially leading to deadly arrhythmias. The objective of this study was to characterize the QT interval prolongation associated with ondansetron use in the Emergency Department.

Methods

This was a prospective, observational cohort study of adult patients who presented to the emergency department during a one-year period and were treated with intravenous ondansetron. We investigated the QT prolongation associated with dosages. ECGs were obtained before the medication and 5, 15, and 30 minutes after IV drug administration. Every QT measurement was recorded and compared to the zero point. The severity of drug-induced QT prolongation was determined according to the recommendations of the International Conference on Compliance (ICH). QTc prolongation was categorized as ‘negligible’ (<5 ms), ‘significant’ (>20 ms), ‘potential concern’ (>30 ms), or ‘definitely worrying’ (>60 ms).

Results

Of the 435 patients enrolled in the study, 60% (261 patients) were female and the mean age was 39 (±18). The QT prolongation peaked at the fifth minute and remained consistent at the fifteenth and thirty-first minutes. The maximum prolongation of the mean QT duration occured at the fifth minute (7.9 ± 18.1 ms). No patient revealed any problems with cardiac conduction. The prolonged QT interval was not related to the dose of ondansetron, but QT measurements were higher in the 30th minute in patients treated with 8 mg of ondansetron. The effect of ondansetron administration on QT prolongation was found to be above the ‘negligible’ but below the ‘significant’ value, according to the ICH recommendations.

Discussion

In this study, QT prolongation due to ondansetron administration was below the ‘important’ value according to the recommendations of the ICH. No cases of cardiac arrhythmia were reported in any of the partients. Thus, routine ECG monitoring in patients given ondansetron due to the risk of QTc prolongation does not seem cost-effective when evaluated together with additional factors such as its negative impact on emergency patient flow, waste of personnel and time, and increase in healthcare costs. In the absence of a known risk of cardiac arrhythmia, IV administration of 4 mg and 8 mg of ondansetron doses no risk of QT prolongation in the emergency population.