Pharmacotherapy of depression: a historical analysis

Iproniazid and imipramine, the prototypes of monoamine oxidase inhibitor (MAOI) and monoamine (re)uptake inhibitor (MAUI) antidepressants, were introduced in 1957. The relationship between iproniazid's antidepressant effect and its MAO inhibiting property was tenuous. Because of the potential drug-drug interactions and the need for dietary restrictions, the use of MAOIs became restricted to atypical depression. The confounding of reserpine reversal with antidepressant effect led to the theory that MAU inhibition is responsible for imipramine's antidepressant effect. Driven by neuropharmacological theory, non-selective reuptake inhibitors were replaced first by selective norepinephrine reuptake inhibitors, then by selective serotonin reuptake inhibitors, and more recently, by a series of new antidepressants to relieve the stimulation of serotonin-5HT2A receptors and the compensatory decline of dopamine in the brain. Each antidepressant has its own identity, but meta-analyses indicate a widening of the antidepressant response range from 65-70% to 45-79%, and a lowering of the antidepressant threshold from 65% to 45%. Although one can no longer expect that 2 of 3 depressed patients will respond to treatment, the newer antidepressants are better tolerated, because they produce less anticholinergic side effects.