In this episode, I’ll discuss the incidence of torsades from low-dose ondansetron in peri-operative patients.
Ondansetron prescribing information has a warning that Electrocardiogram (ECG) changes including QT interval prolongation have been seen in patients receiving ondansetron.
Some references list this as a concern, but many clinicians believe that a low dose of 4 mg does not represent a significant risk for most patients.
Researchers at the Department of Anesthesiology, Mayo Clinic College of Medicine, Rochester, Minnesota recently published a single center review evaluating the risk of torsades from a 4 mg dose of ondansetron IV in peri-operative patients.
Over 32,000 patients were analyzed in this retrospective single-center review.
The analysis identified all patients with a QTc >450 milliseconds, any ventricular tachycardia (including torsades) within 48 hours of receiving ondansetron, and death within 7 days of receiving ondansetron.
In this large cohort which spanned a 2 year collection period, not one patient developed torsades or died as a result of ondansetron administration.
There were 46 patients in the cohort of over 32,000 that developed monomorphic ventricular tachycardia. However, 100% of these episodes were precipitated by existing cardiovascular disease and 50% of these episodes had documented monomorphic VT prior to receiving ondansetron. There were 32 deaths in the cohort however these were all judged to have been precipitated by pre-existing disease.
This data should reassure concerned clinicians that low-dose ondansetron use in peri-operative patients does not come with a risk of torsades, ventricular tachycardia, or death beyond that of the baseline risk in this population.
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