Psychiatry makes use of a wide range of medications, such as anti-epileptic drugs in the treatment of affective disorders, impulsive behavior or epilepsy. The authors aim to present a particular clinical presentation in order to reinforce the awareness of the side effects of our prescriptions.

54 year-old man, epileptic, medicated with Sodium Valproate (VPA) and Phenobarbital, admitted to our hospital due to insomnia, irritability and aggressiveness with two weeks of duration. Early evaluations showed disorientation, slow and poor speech, and prejudice ideas towards his family. Disequilibrium, asterixis and slurred speech imposed evaluation by Neurology. Analytic evaluations demonstrated high phenobarbital and ammonia levels. Both anti-epileptics were slowly withdrawn, with clinical resolution.

VPA may be associated with elevation of ammonia levels, and eventually with encephalopathy without evidence of liver failure. There is a wide range of clinical presentations of hyperammonemic encephalopathy ranging from decreased level of consciousness, irritability, agitation, focal neurological deficits, cognitive slowing, vomiting, drowsiness, and lethargy. On the other hand, high doses of phenobarbital may have similar presentations which could be potentiated by VPA.

There was a good correlation between the fall in serum ammonia levels, clinical improvement, and anti-epileptics withdrawal, suggesting the implication of medication in this clinical picture. The case illustrates the need to check ammonia and anti-epileptic levels, and to consider this diagnosis in patients taking VPA and Phenobarbital who present with new neuropsychiatric manifestations.