Plasma nortriptyline and clinical response in depression

Plasma levels of nortriptyline below 50 ng/ml or above 150 ng/ml have been reported to yield results inferior to intermediate levels. In the present study, patients with uncomplicated primary, nonbipolar depression were randomly assigned to 12 weeks of treatment with NT alone or with cognitive therapy. Nine of 35 patients had mean NT plasma levels less than 50 ng/ml. Five of them improved clinically to the criterion level of less than or equal to 7 on the Hamilton Rating Scale for Depression. This improvement rate was not at all different from that of patients with mean plasma levels within the presumed therapeutic window. The upper limit of 150 ng/ml was not tested. This study is presented in the hope of reviving the apparently dormant search for optimal therapeutic plasma levels of antidepressants.