Final answer:
The mechanism of action of ketamine prescribed for major depressive disorder is as an N-methyl-d-aspartate (NMDA) receptor antagonist, which leads to modulation of depression symptoms and can result in rapid antidepressant effects.
Step-by-step explanation:
Mechanism of Action of Ketamine for Major Depressive Disorder
The mechanism of action of ketamine prescribed for major depressive disorder is N-methyl-d-aspartate (NMDA) receptor antagonist. Unlike Selective Serotonin Reuptake Inhibitors (SSRIs) and Monoamine Oxidase Inhibitors (MAO inhibitors), which increase neurotransmitters like serotonin and norepinephrine in the synaptic cleft by preventing reuptake or degradation, ketamine binds to and inhibits NMDA receptors. This blockade leads to a cascade of events that ultimately modulate depression symptoms. Clinical evidence suggests that the use of ketamine can result in rapid antidepressant effects, which contrasts with the typically slower onset of traditional antidepressants like SSRIs and MAO inhibitors.