Paliperidone overdose with delayed onset of toxicity.

Paliperidone, or 9-hydroxy risperidone, is the newest atypical antipsychotic agent to be approved for use by the Food and Drug Administration. Despite being the primary active metabolite of risperidone, paliperidone differs in several ways from risperidone. The most notable difference is that paliperidone is formulated as an extended-release product. We present a case of a 14-year-old, 59-kg girl with a history of psychosis and major depressive disorder who developed toxicity after an ingestion of 180 mg (3.1 mg/kg) of paliperidone. This case is not only one of the first cases of paliperidone overdose described in the literature but also is unique in that it describes delayed onset of toxicity, as well as extended duration of symptoms.