Valproate-induced hyperammonemic encephalopathy in an elderly patient with bipolar disorder

Hyperammonemia is a rare side effect of valproate, diagnosis of which requires a high level of clinical suspicion. We describe a case of 57-year-old man, suffering from bipolar affective disorder, who had multiple physical comorbidities (diabetes mellitus, benign prostatic hyperplasia, hydroureteronephrosis, and chronic kidney disease) and was on sodium valproate 1500 mg/day along with risperidone 6 mg/day, who developed delirium when the dose of sodium valproate was increased from 1500 mg/day to 2000 mg/day. In view of use of high doses of valproate, hyperammonemia was suspected, and on investigations, patient was found to have high ammonia levels (159 μmol/l). He was managed conservatively with stoppage of valproate and syrup lactulose. To conclude this case depicts that use of high doses of valproate can lead to hyperammonemia, especially among those with chronic medical illnesses.