Relation between drug-induced central nervous system effects and plasma levels of diazepam in man.

Pharmacodynamic effects and plasma levels of diazepam were studied in healthy male volunteers at different dose levels. Responses to diazepam were quantified, using instruments which measured body sway (statometry) and psychomotor performance (stressalyser tests). High dose-related correlations were obtained between drug-induced changes in test parameters and drug plasma levels, both with regard to stimulant and depressive effects. Techniques were devised for evaluating and comparing the efficacy and usefulness of different types of tests, taking into account critical thresholds, slopes and error estimates, correcting for changes in predrug levels and control (nondrug) trials.