A selective norepinephrine reuptake inhibitor (IC₅₀s = 8.2 nM) that displays greater than 1,000-fold affinity for binding rat norepinephrine receptors compared to serotonin, histamine, acetylcholine, or dopamine receptors (Kis = 1.1, 129, 1,400, 3,900, and >10,000 nM, respectively).