Isocarboxazid (Marplan, Marplon, Enerzer) is a non-selective, irreversible monoamine oxidase inhibitor (MAOI) of the hydrazine class used as an antidepressant. Along with phenelzine and tranylcypromine, it is one of only three classical MAOIs still available for clinical use in the treatment of psychiatric disorders in the United States, though it is not as commonly employed in comparison to the others.
Isocarboxazid is primarily used to treat mood and anxiety disorders. It has also been investigated in the treatment of Parkinson’s disease and other dementia-related disorders. Isocarboxazid, as well as other MAOIs, increase the levels of the monoamine neurotransmitters serotonin, dopamine, and norepinephrine in the brain.