Sodium valproate: serial monitoring of EEG and serum levels.

The clinical and electroencephalographic (EEG) effects of sodium valproate were studied in four patients by means of serial 24-hour EEG recordings and simultaneous hourly determinations of serum drug concentrations. The patients all had frequent clinical seizures and generalized spike-wave discharges. Valproate appeared to reduce diurnal paroxysmal discharges (PD) and clinical seizures, but the effect on nocturnal PD was less marked. The extent and duration of the depression of PD and seizures varied. Altering the distribution of the total daily dose may change the pattern of clinical seizures and PD. Valproate concentrations fluctuated widely over 24 hours, and the significance of single estimations often cited in the literature appears dubious. Peak serum concentrations above 100 micrograms per milliliter may be necessary in some patients to achieve clinical and EEG improvement.