Isocarboxazid, also known as Marplan, is an antidepressant from the monoamine oxidase inhibitors (MAOIs) drug class. This drug is indicated in different disorders like major depression, dysthymic disorder, atypical disorder, panic disorder, and phobic disorders. Isocarboxazid inhibits the MAO in the brain, resulting in the relief of depressive symptoms. The monoamine oxidase is an enzyme that catalyzes the oxidative deamination of many amines like serotonin, norepinephrine, epinephrine, and dopamine. There are 2 isoforms of this protein: A and B. The first one is found in cells located in the periphery and breakdown serotonin, norepinephrine, epinephrine, dopamine, and tyramine. The second one, the B isoform, breakdowns phenylethylamine, norepinephrine, epinephrine, dopamine, and tyramine. This isoform is found in the extracellular tissues and mostly in the brain. The mechanism of action of the MAOIs is still not determined, it is thought that they act by increasing free serotonin and norepinephrine concentrations and/or by altering the concentrations of other amines in the CNS. MAO A inhibition is thought to be more relevant to antidepressant activity than the inhibition caused by MAO B. Selective MAO B inhibitors have no antidepressant effects. This drug is administered as an oral tablet.

Isocarboxazid Amine Oxidase Serotonin Antidepressant Pathway References