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Isocarboxazid structure.svg
Clinical data
Trade namesMarplan
AHFS/Drugs.comConsumer Drug Information
Routes of
ATC code
Legal status
Legal status
  • AU: S4 (Prescription only)
  • In general: ℞ (Prescription only)
Pharmacokinetic data
BioavailabilityLow, peak at 1-2 h[1]
MetabolismLiver (Carboxylesterase[3])
MetabolitesHippuric acid[2]
Elimination half-life1.5-4h[1]
  • N′-benzyl-5-methylisoxazole-3-carbohydrazide
CAS Number
PubChem CID
CompTox Dashboard (EPA)
ECHA InfoCard100.000.399 Edit this at Wikidata
Chemical and physical data
Molar mass231.255 g·mol−1
3D model (JSmol)
  • O=C(NNCc1ccccc1)c2noc(c2)C
  • InChI=1S/C12H13N3O2/c1-9-7-11(15-17-9)12(16)14-13-8-10-5-3-2-4-6-10/h2-7,13H,8H2,1H3,(H,14,16) checkY
 ☒NcheckY (what is this?)  (verify)

Isocarboxazid (Marplan, Marplon, Enerzer) is a non-selective, irreversible monoamine oxidase inhibitor (MAOI) of the hydrazine class used as an antidepressant.[4] 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,[5][6] though it is not as commonly employed in comparison to the others.[5][6]

Isocarboxazid is primarily used to treat mood and anxiety disorders. It has also been investigated in the treatment of schizophrenia,[7] Parkinson's disease and other dementia-related disorders.[8]

Isocarboxazid, as well as other MAOIs, increase the levels of the monoamine neurotransmitters serotonin, dopamine, norepinephrine, epinephrine, melatonin, phenethylamine in the brain.[9]

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MAOIs, including isocarboxazid, are used only rarely due to prominent food and drug interactions and have been largely superseded by newer antidepressants such as the selective serotonin reuptake inhibitors (SSRIs).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.

See also[edit]


  1. ^ a b "Isocarboxazid". Retrieved 27 October 2021.
  2. ^ "Reaction: Isocarboxazid to 1 product". Retrieved 27 October 2021.
  3. ^ K Moroi; T Kuga (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. PMID 6178187.
  4. ^ Fagervall I, Ross SB (April 1986). "Inhibition of monoamine oxidase in monoaminergic neurones in the rat brain by irreversible inhibitors". Biochemical Pharmacology. 35 (8): 1381–7. doi:10.1016/0006-2952(86)90285-6. PMID 2870717.
  5. ^ a b David Rosenberg (21 August 2013). Pocket Guide For The Textbook Of Pharmacotherapy For Child And Adolescent Psychiatric Disorders. Routledge. pp. 176–. ISBN 978-1-134-86002-9.
  6. ^ a b Lawrence A. Labbate; Maurizio Fava; Jerrold F. Rosenbaum; George W. Arana (28 March 2012). Handbook of Psychiatric Drug Therapy. Lippincott Williams & Wilkins. pp. 99–. ISBN 978-1-4511-5307-1.
  7. ^ F. Darling, Harry (1 April 2006). "Isocarboxazid (marplan) in ambulatory psychiatric patients". The American Journal of Psychiatry. 116 (4): 355–356. doi:10.1176/ajp.116.4.355. PMID 13814129. Retrieved 22 October 2021.
  8. ^ Riederer, Peter; Laux, Gerd (31 March 2011). "MAO-inhibitors in Parkinson's Disease". Experimental Neurobiology. Experimental Neurology. 20 (1): 1–17. doi:10.5607/en.2011.20.1.1. PMC 3213739. PMID 22110357.
  9. ^ Volz, Hanz-Peter. (November 1998) “Monoamine Oxidase Inhibitors A Perspective on Their Use in The Elderly” Biochemical Pharmacology (5) 341-352.