[Alterations of the state of consciousness induced by valproic acid: 6 case reports]

Six epileptic patients are described to whom the addition of Valproic Acid (VPA) to a previously unsatisfactory antiepileptic treatment caused a toxic encephalopathy. This was characterized by alterations of the state of consciousness in all patients a few days after the beninning of the treatment with VPA. These ranged from a marked drowsiness to coma and were often associated with gastrointestinal and neurological (ataxia, asterixis) symptoms. In all cases very high blood ammonia values were found and the EEGs showed a diffuse slowing down of the activity. After the discontinuation of the drug the toxic symptoms quickly ceased and ammonia values returned to the normal values. It is hypothesized that the interference of VPA on the metabolism of ammonia could play an important role in the pathogenesis of the VPA-induced toxic encephalopathy.