Validation of a therapeutic plasma level range in amitriptyline treatment of depression

In the course of a double-blind study, 29 depressed patients received amitriptyline 150 mg/day for 4 weeks. Scores on the Hamilton Depression Rating Scale were assessed before treatment and after 2 and 4 weeks, and plasma levels of amitriptyline, nortriptyline, and (E)-10-hydroxynortriptyline were monitored weekly. Response reflected by percent reduction of Hamilton Depression Rating Scale score and by final score was better at steady-state amitriptyline + nortriptyline concentrations of 125-210 ng/ml than at lower and higher plasma levels. This applied to the total group and to the subgroup of 22 female patients. The data confirm the results of a previous study performed in the same hospital. An influence of the (E)-10-hydroxynortriptyline concentration in plasma on therapeutic outcome was not discernible. The results suggest that plasma level monitoring may be helpful when patients do not respond to conventional amitriptyline doses.