[Hyperammonemia in valproate therapy in children and adolescents]

In order to evaluate significance and frequency of valproic acid (VPA)-induced hyperammonemia we measured venous serum ammonia, SGOT, G-GT, platelets and antiepileptic drug levels in three groups of subjects: 1.) 30 pediatric patients treated with VPA, alone or in combination 2.) 30 healthy age and sex matched subjects 3.) 30 pediatric unselected patients treated with various antiepileptic drugs except VPA. In the VPA group serum ammonia was significantly (p less than 0.01) higher than in controls and in the group 3. Patients on VPA-polytherapy had significantly higher serum ammonia values than patients on VPA-monotherapy (p less than 0.01). Hyperammonemia was found in 8 (27%) VPA-treated patients. A syndrome consisting of lethargy, stupor, hypotonia and increased seizure activity developed in 3 patients on VPA-therapy of whom two showed hyperammonemia. After discontinuing VPA this syndrome disappeared in all three cases. There was no direct correlation between VPA and ammonia levels. The etiology of hyperammonemia in VPA treated patients is not yet fully explained. It may be related to the fatal VPA induced hepatic failure reported in the literature. Some risk factors which may facilitate hepatic injury during VPA therapy (young age, co-medication, polytherapy, infectious disease, protein overload, low caloric intake) are discussed and some practical consequences are indicated.