antidepressant
n. any drug administered in the treatment of depression. Most antidepressants work by increasing the availability of monoamine neurotransmitters such as norepinephrine, serotonin, or dopamine, although they do so by different routes. The monoamine oxidase inhibitors (MAOIs) work by inhibiting monoamine oxidase, one of the principal enzymes that metabolize these neurotransmitters. Most of the other antidepressants, including the tricyclic antidepressants (TCAs) and the selective serotonin reuptake inhibitors (see SSRI), inhibit the reuptake of serotonin or norepinephrine (and to a much lesser degree dopamine) into the presynaptic neuron. Either process leaves more of the neurotransmitter free to bind with postsynaptic receptors, initiating a series of events in the postsynaptic neuron that is thought to produce the actual therapeutic effect. In 2007, a boxed warning was added to the labeling of all antidepressants,
stating that the risk of suicidal thinking and actual suicide increased in children, adolescents, and young adults taking antidepressants versus those taking placebo in short-term studies of major depressive disorder and that, since depression itself is associated with an increased suicide risk, all patients newly on antidepressant medications should be monitored appropriately.