Blood ammonia level during valproic acid therapy.

We determined the blood ammonia level of epileptic patients in relation to valproic acid (VPA) therapy. A total determination of 256 specimens obtained from 174 cases were analyzed. The materials were assigned to the following three treatment groups: (a) VPA-monotherapy, (b) VPA-polytherapy and (c) non-administration of VPA. The distribution ranges of the blood ammonia level (micrograms/dl) were 40.5, 56.6 and 40.7 in mean, respectively. The VPA-polytherapy group showed a significantly higher level compared with the other two groups. On the other hand, the latter two groups showed no difference. There was a positive relationship between the blood ammonia and VPA serum levels with statistical significance. In conclusion, a critical factor causing hyperammonemia seemed to be the multiple use of antiepileptic drugs including VPA.