Clinical significance of monitoring plasma levels of psychotropic drugs.

The possible clinical significance of plasma level monitoring of psychotropic drugs in psychotic patients is described. In particular, data obtained with children and 'resistant' psychotic patients are presented. The results in children indicate the existence of a good relationship between side-effects and haloperidol plasma levels as well as between adverse effects and chlorimipramine plasma levels. Furthermore, an age effect on haloperidol clearance could be shown. Relationship between haloperidol and chlorimipramine concentration and effects could be observed for tics and enuresis respectively but not for psychotic reactions. Data in adult patients illustrate on the one hand possible causes of variability in plasma levels of haloperidol and, on the other hand, the fact that poor bioavailability is not the cause of lack of response in 'resistant' schizophrenic patients.