Valproic-induced Hyperammonemic Encephalopathy in a Known Case of Epilepsy

Valproic acid, a broad-spectrum anticonvulsant drug, commonly causes elevated ammonia levels, which is usually asymptomatic in most cases. On rare occasions, potentially fatal hyperammonemia-induced encephalopathy can occur. We present a case of a 24-year-old female who presented to the emergency department with status epilepticus that was being managed with valproic acid. Further workup was done because of prolonged postictal state, which revealed increased ammonia levels; she was eventually diagnosed with valproic-induced hyperammonemic encephalopathy. Discontinuing valproic acid resulted in drastically improved symptoms and a gradual decline in ammonia levels. A clinician should be aware of rare drug adverse effects and drug interactions to conclusively reach the correct diagnosis. A prolonged postictal state should warrant further workup to rule out other possible etiologies.