Acute effects of diphenylhydantoin in relation to plasma levels: Behavioural and psychophysiological studies

Synopsis Two double-blind experiments are reported in which different doses of diphenylhydantoin were compared with placebo. Drug effects on tests, psychophysiological measures, and self-ratings of mood were studied in normal subjects and related to plasma levels of the drug and psychasthenic personality traits. Significant sedative effects were obtained in some self-rating variables. The combined effect in the objective psychological tests was significantly correlated (rank) to the plasma level in the higher dose experiment.