Altered Mental Status and Hyperammonemia after Overdose of Valproic Acid with Therapeutic Valproic Acid Concentrations

Valproic acid is used in the treatment of multiple disorders. Adverse effects from valproic acid include hepatotoxicity, hypotension, metabolic acidosis, and decreased mental status. Valproic acid also causes hyperammonemia. Many physicians assume that this is due to a supratherapeutic valproic acid concentration; when in fact, it can occur with therapeutic valproic acid concentrations. This is because the hyperammonemia may be related to carnitine deficiency and disruption of the urea cycle, which can both occur with therapeutic valproic acid concentrations. We report a patient presented to the emergency department with alteration of mental status after ingesting valproic acid for recreational purposes, who developed hyperammonemia with a therapeutic valproic acid concentration.