Clozapine Toxicity in Two Young Siblings Due to a Pharmacy Dispensing Error: a Pediatric Case Report

Clozapine is an atypical antipsychotic used to treat refractory schizophrenia; in both therapeutic use and overdose, it can cause significant toxicity. We report two young siblings who developed altered mental status after ingesting clozapine due to a pharmacy dispensing error.

A 5-year-old girl and her 19-month-old sister presented to the emergency department (ED) with altered mental status after they took their first dose of what was believed to be cimetidine, prescribed to treat molluscum contagiosum. Both children were discharged after a brief period of observation in the ED. Two days later, when the older child continued to be symptomatic, their mother used a web-based pill identifier and discovered that the pills dispensed by the pharmacy were 200 mg clozapine tablets, not the cimetidine that had been prescribed. Ingestion was confirmed with an elevated serum clozapine concentration in the older child of 17 mcg/L at 85 hours post-ingestion (adult therapeutic range: 350-600 mcg/L). Both children had complete resolution of their symptoms 4 days following the ingestion with supportive care alone.

We report two cases of pediatric clozapine toxicity due to a pharmacy dispensing error. The error was due, in part, to similarly named medications being stored adjacent to each other on a shelf. Dispensing errors are not rare occurrences and their root causes are multi-factorial. This case demonstrates the importance of reducing such errors, particularly for medications with potential for severe toxicity.