Ex vivo receptor binding as a function of time was determined in Charles River rats. The pharmacokinetic and protein binding parameters in man as well as the ex vivo receptor binding parameters in rat brain for three benzodiazepine induction agents, diazepam, lorazepam and midazolam, were used to develop and test a pharmacokinetic/pharmacodynamic/receptor binding model. The model was subsequently used to predict changes in receptor binding and pharmacodynamics as a function of changes in pharmacokinetics. The model was found to be a good predictor of the relative onset and duration of the sedative and amnesic properties in normal subjects as well as in the presence of certain patho-physiological conditions and certain drug interactions.