A multiparametric investigation of daytime sleepiness and psychomotor functions in epileptic patients treated with phenobarbital and sodium valproate: a comparative controlled study

Subjective and objective measures of daytime sleepiness and psychomotor function were determined in normal control subjects and in epileptic patients on chronic monotherapy with phenobarbital or valproate (n = 10 in each group). All patients had primary generalized epilepsy with a normal resting EEG and were seizure-free for at least 1 year. After nocturnal polysomnographic recording, each subject was evaluated at 2 h intervals between 10:00 and 16:00 h by using multiple sleep latency tests (MSLT), a visual analogue rating scale for alertness (VARS), an anxiety scale (STAI-X1) and a battery of psychomotor tests. Nocturnal sleep parameters before daytime assessment were comparable in the 3 groups. At MSLT, patients on phenobarbital showed a shorter mean sleep latency (9.0 +/- 1.7 min) compared with the valproate group (12.5 +/- 1.3 min) and controls (12.9 +/- 1.2 min), though within-group variability was considerable. Compared with controls, patients on phenobarbital showed longer motor movement times, impaired attention (cancellation test, CT), reduced processing speed (digit-symbol substitution, DSS) and a trend towards lower critical flicker fusion threshold. Patients on valproate showed some impairment in attention and a trend towards longer motor movement time. In patients, no correlation was found between assessed parameters and serum drug concentrations, which were 19.3 +/- 1.7 micrograms/ml for phenobarbital and 85.7 +/- 4.7 micrograms/ml for valproic acid.