Classical MAOIs, including isocarboxazid, are used only rarely due to prominent food and drug interactions and have been largely superseded by newer antidepressants such as the selective serotonin reuptake inhibitors (SSRIs). The cause of the interactions is because MAOIs inhibit the metabolism of dietary amines (e.g., tyramine) and the monoamine neurotransmitters. In combination with other drugs that increase the levels of the monoamine neurotransmitters such as the SSRIs, or with certain foods high in dietary amines such as aged cheeses, MAOIs can produce dangerous elevations of monoamine neurotransmitters resulting in potentially life-threatening syndromes such as hypertensive crisis and serotonin syndrome.
^Moroi K, Kuga T (April 1982). "Inhibitory effect of leptophos on carboxylesterase (isocarboxazid amidase) in rat liver". Toxicology Letters. 11 (1–2): 81–85. doi:10.1016/0378-4274(82)90110-2. PMID6178187.
^Fagervall I, Ross SB (April 1986). "Inhibition of monoamine oxidase in monoaminergic neurones in the rat brain by irreversible inhibitors". Biochemical Pharmacology. 35 (8): 1381–1387. doi:10.1016/0006-2952(86)90285-6. PMID2870717.
^Darling HF (October 1959). "Isocarboxazid (marplan) in ambulatory psychiatric patients". The American Journal of Psychiatry. 116 (4): 355–356. doi:10.1176/ajp.116.4.355. PMID13814129.