Effect of sodium valproate on psychomotor performance in children as a function of dose, fluctuations in concentration, and diagnosis.

Forty-six children receiving sodium valproate monotherapy, and with well-controlled seizures, were tested three times, at weekly intervals in the morning, on an extensive battery of psychomotor tests. The first session was a practice session to minimize subsequent practice effects. On one of the remaining 2 test days, morning medication was delayed until after testing (low concentration condition), whereas sodium valproate was given before testing on the alternate session (high concentration day). The data were analyzed for the effects of diagnosis (partial vs. generalized epilepsy), dose (above or below 20 mg/kg/day), and time of medication (low and high drug concentration days). Four variables discriminated between the diagnostic groups, all favoring children with generalized epilepsy. Another four measures were significantly associated with dose, with those on lower doses performing at a superior level. Time of medication had virtually no effect on performance, however. The findings were related to previous diagnostic and dosage research. Although a deterioration in performance at higher doses appears to be consistent with other dosage research, the absence of an effect due to time of medication suggests that performance does not fluctuate between drug administrations.