Abstract
Valproic acid (VPA) is widely used to prevent posttraumatic epilepsy in patients with traumatic brain injury. Hyperammonemia is a well-known complication of VPA medication. We report a case in which hyperammonemia was observed even at VPA concentrations below the therapeutic range, and normalized immediately after VPA administration ceased. An 18-year-old male was in a traffic accident. The patient’s computed tomography scan revealed a contusional hematoma in the right temporal lobe and a traumatic subarachnoid hemorrhage. To prevent posttraumatic epilepsy, he was administered fosphenytoin (intravenous) for 1 week, and then administered VPA (oral, 1,200 mg daily). At 4 days after the beginning of VPA administration, the patient’s laboratory examination revealed serum VPA 27 μg/ml and plasma ammonia 67 μmol/l. At 16 days after treatment initiation, serum VPA and plasma ammonia had risen to 52 μg/ml and 165 μmol/l, respectively. No obvious symptoms or signs of hyperammonemia were recognized. The patient’s ammonia levels normalized within 2 days after ceasing VPA. Therefore, we concluded that therapeutic monitoring including a plasma ammonia level is recommended for any patient taking VPA medication, regardless of serum VPA concentration.
