Background: Ondansetron is a commonly prescribed 5-HT 3 antagonist used in the management of nausea and vomiting. Little is known about its potential adverse effects following an overdose; however, it has a well-established safety profile at therapeutic doses. We describe a case of a toddler who ingested a large quantity of ondansetron resulting in tachycardia, altered mental status, and QTc prolongation.
Case Report: A 15-month-old boy ingested a maximum of 18 ondansetron tablets prescribed to his mother from a bottle containing a mixture of 4 and 8 mg tablets. No other medications were accessible and no emesis was reported. After arrival to the Emergency Department, he was noted to be irritable with flushed skin, and tachycardic with a pulse between 170 and 190 beats/min. His initial ECG demonstrated sinus tachycardia with a QRS duration of 40 msec and a prolonged QTc of 490 msec. The patient subsequently became intermittently somnolent and agitated. Eight hours post-ingestion the patient was much improved with a heart rate of 120 beats/min and behaving normally. The child was observed overnight and discharged to home 19 hours post-ingestion; at the time of discharge, he was asymptomatic, had normal vital signs, and his QTc prolongation had resolved. He received no pharmacotherapy during his hospitalization.
Discussion: The potential for pediatric exposures to ondansetron and risk for subsequent toxicity is increased, paralleling the rise in physician prescribing patterns for both children and adults. Despite its well-established therapeutic safety profile in adults, knowledge of toxicity in pediatric patients is limited. This case demonstrates that acute ondansetron toxicity in a toddler may result in somnolence, tachycardia, and prolongation of the QTc interval. These symptoms, though rare, have previously been reported in a 12-month-old male who also developed seizures, hepatoxicity, and serotonin syndrome following the unintentional ingestion of 56-64 mg of ondansetron.
Conclusion: Healthcare providers should recognize the risk for acute toxicity following ondansetron overdose. This case illustrates a probable association between this commonly prescribed medication and the development of tachycardia, altered mental status, and QTc prolongation in an exposed toddler.