Life-threatening pediatric dextromethorphan polistirex overdose

Dextromethorphan polistirex is an extended-release formulation of dextromethorphan hydrobromide, marketed as Delsym® (Reckitt; Parsippany, NJ), with a duration of action roughly two to three times that of the standard formulation. The polistirex binder is responsible for the prolonged duration of action by slowing the release of active ingredient; the liberated dextromethorphan has unchanged pharmacokinetics and clinical effects. A 23-month-old male presented following a 900 mg (71.4 mg/kg) dextromethorphan polistirex ingestion 90 min prior. On arrival, he was unresponsive, tachycardic, and hypertensive with mydriasis, roving eye movements, rotary nystagmus, and opisthotonos. Approximately 90 min after arrival, he required intubation for airway protection. The blood dextromethorphan concentration from 75 min after arrival was 110 ng/mL (10-40 ng/ml therapeutic). He was extubated approximately 13 h after arrival and discharged that day. Most pediatric dextromethorphan overdoses produce mild symptoms that are not considered to be life-threatening. Life threatening overdoses are rare. The toxic dextromethorphan dose and blood concentration as well as the toxicokinetics of the polistirex formulation are not well defined. Our case suggests that a blood dextromethorphan concentration exceeding 100 ng/mL can be toxic in this age group, however further study is needed.