Dual monoamine modulation for improved treatment of major depressive disorder

The worldwide scope of depressive illness and lack of fully effective pharmacotherapy mandates significant improvements in treatment paradigms. Current antidepressant medications remain limited by poor efficacy, slow onset of action, and untoward side effects. While the introduction of serotonin-specific reuptake inhibitors (SSRIs) offered significant improvements in tolerability, no improvements in efficacy or speed of onset have been made relative to the traditional and poorly tolerated tricyclic antidepressants (TCA). The dominant efforts toward improving antidepressant medications are guided by cumulative evidence from neurochemical and clinical studies supporting the therapeutic potential of enhancing monoamine function in depression. A number of novel antidepressant drugs, including mirtazapine, milnacipran, venlafaxine, and duloxetine have been developed based on their interaction with both 5-HT and NE. Current clinical evidence suggests that these new agents may offer improved efficacy and/or faster onset of action compared with SSRIs and an improved side effect profile compared with TCAs. Potential neurobiological substrates mediating the enhanced antidepressant activity of dual reuptake inhibitors are discussed.