Hyperammonemia and Coma without Hepatic Dysfunction Induced by Valproate Therapy

The authors report a case of a 41‐year‐old mentally disabled man with bipolar disorder who presented to the emergency department with altered mental status. He was found to have a significantly elevated ammonia level (377 μM/L) with no signs of hepatic insufficiency. His coma and hyperammonemia were attributed to his chronic valproate therapy. This patient had the highest serum ammonia level ever reported with a therapeutic valproate level in the absence of any other anticonvulsant therapy, metabolic abnormality, or hepatic dysfunction. The authors discuss this case and review the current literature on hyperammonemia in valproic acid therapy and the use of L‐carnitine in these patients.