Excessive Sedation and Catatonia-Like Presentation From Risperidone-Valproate Interaction: A Case Report.

Sedation is a known adverse effect of risperidone, but catatonia-like immobility potentiated by valproate is rarely reported. A 23-year-old woman with bipolar disorder, admitted for acute psychosis, was treated with risperidone titrated to 3 mg twice daily alongside valproate. She developed escalating somnolence, immobility, refusal of food, and tremors. Laboratory evaluation revealed a supratherapeutic valproate level (125 µg/mL); medical workup and a lorazepam challenge were unrevealing. Discontinuation of risperidone with substitution with olanzapine resulted in rapid and complete recovery within 24 hours. This case highlights the risk of severe catatonia-like sedation from a risperidone-valproate interaction. It underscores the importance of recognizing medication-induced causes of catatonia-like presentations to enable timely intervention.