Tricyclic antidepressants and supine, standing, and exercise plasma norepinephrine levels

Fourteen depressed patients were treated for 1 to 8 wk (4.1 +/- 0.6, mean +/- SEM) with imipramine, doxepin, or amitriptyline to study the effects of tricyclic antidepressants (TCAs) on sympathetic nervous system (SNS) function. Eight had chronic but medically stable cardiac disease and six were medically healthy. Supine plasma norepinephrine (NE) and epinephrine (EPI) levels, mean arterial blood pressure (MAP), and heart rate were measured at rest, after standing, and during graded, supine maximal bicycle exercise. Eight nondepressed patients with cardiac disease were studied without drug intervention as controls. There were no baseline differences in any of these measures among the medically healthy depressed subjects, the depressed cardiac patients, and the eight nondepressed patients matched for cardiac disease. After TCAs, NE was increased by 51 +/- 6% of basal values and heart rate rose, but EPI and MAP were unchanged. The supine to 10-min standing increment in NE increased from 309 +/- 51 pg/ml at baseline to 406 +/- 55 pg/ml during TCA treatment. These findings are compatible with an increase in SNS outflow after TCAs.