Diazepam and desmethyldiazepam plasma concentrations in chronic anxious outpatients.

Within the framework of a large-scale clinical study on the effect of diazepam in chronic anxiety, diazepam (D) and desmethyldiazepam (DD) plasma concentrations were determined frequently. Significant relationships were found between the clinical effect and the plasma concentrations of D and DD, respectively; a curvilinear relationship resulted if the dosage was disregarded, but within the individual dosage groups the relationship was found to be linear. For these computations, the daily diazepam dose was treated as a covariable in a factorial analysis of variance approach. It was found, in addition, that the daily diazepam dose was one of the most significant predictors of the plasma concentration of D or DD, respectively. The steady state plasma concentrations were highest in patients experiencing an exacerbation of their conditions of anxiety if they were returned to placebo after 14 to 22 weeks of diazepam medication. The lowest steady state concentrations were found with those patients who showed withdrawal symptoms under these conditions.