Antidepressants have seven distinct mechanisms of action.
Pharmacologic mechanisms allow antidepressants to be separated into seven classes identifying both the therapeutic actions and the side effects of antidepressants currently available. The selective norepinephrine and dopamine reuptake inhibitor bupropion defines a novel class of antidepressant that has no direct actions on the serotonin system. In a randomized, placebo-controlled, double blind study comparing the selective noradrenaline reuptake inhibitor, reboxetine, with the selective serotonin reuptake inhibitor, fluoxetine, reboxetine was found to be superior to both placebo and fluoxetine. Overall, noradrenergic therapy seems most effective in improving negative self-perception and motivation towards action, resulting in a better quality of remission in terms of social functioning. Reboxetine is as effective as fluoxetine in the overall depressed population and superior in severely depressed patients.