Milnacipran: A comparative analysis of human monoamine uptake and transporter binding affinity

Background: Though selective serotonin reuptake inhibitors have revolutionized the field of psychiatry with demonstrated efficacy in affective and anxiety disorders with minimal side effects, norepinephrine-serotonin reuptake inhibitors may provide efficacy similar to tricyclic antidepressants without the adverse side effects associated with tricyclic antidepressants. Methods: The affinity and selectivity of milnacipran, duloxetine, venlafaxine, citalopram, amitriptyline, and nortriptyline were determined for the human serotonin, norepinephrine, and dopamine transporters. Results: Both milnacipran and duloxetine were potent inhibitors of serotonin and norepinephrine uptake. Unlike duloxetine and venlafaxine, milnacipran appears serotonin transporter selective in binding (ratio = 2.61) and norepinephrine transporter selective in uptake (ratio = .45). Conclusions: Milnacipran's binding and uptake inhibition profile more closely resembles that of the tricyclic antidepressants than that of duloxetine. Whether these differences observed in vitro manifest themselves in vivo is not clear.