Quantitative EEG effects and plasma concentration of sodium valproate: acute and long-term administration to epileptic patients.

The quantitative background EEG effects (power spectral analysis) and plasma concentration of sodium valproate were studied after acute single-dose administration and during long-term single-drug treatment, in 10 previously untreated epileptic patients with generalized nonconvulsive seizures. A transient decrease of the signal amplitude (preponderant on anterior scalp areas) and of the 12.5 to 45.0-Hz relative power (limited to the posterior electrode derivations) was observed during the first weeks of chronic treatment. These EEG effects were not correlated with the drug plasma concentration levels or with the occurrence of behavioral side effects (e.g. drowsiness), while being concomitant with the reduction of specific epileptic EEG phenomena. Opposite trends of variation were observed after single-dose acute administration, though with limited statistical significance across subjects.