Phenelzine is an antidepressant and mania drug, which is a monoamine oxidase inhibitor. Its antidepressant effect is similar to that of niacinamide. It can reduce the degradation of catecholamines (norepinephrine, dopamine, and serotonin) in the brain and increase the content of catecholamines. , and play an antidepressant effect. It has a good effect on endogenous depression but has a poor effect on exogenous and reactive depression.