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Monoamine oxidase inhibitors (also known as MAOIs) are a class of drugs which inhibit the activity of the monoamine oxidase enzyme family. They have a long history of use as medications prescribed for the treatment of depression and are particularly effective in treating atypical depression.[1] They are also used in the treatment of Parkinson's disease and several other disorders.[citation needed]

Mechanism of action

MAOIs act by inhibiting the activity of monoamine oxidase, preventing the breakdown of monoamine neurotransmitters and thereby increasing their availability. There are two isoforms of monoamine oxidase, MAO-A and MAO-B. MAO-A preferentially deaminates serotonin, melatonin, adrenaline, and noradrenaline. MAO-B preferentially deaminates phenylethylamine and trace amines. Dopamine is equally deaminated by both types.[citation needed]


The early MAOIs inhibit monoamine oxidase irreversibly, meaning they permanently deactivate it and the enzyme cannot function until it has been replaced by the body, which can take about two weeks. A few newer MAOIs, known as reversible inhibitors of monoamine oxidase A (RIMAs), are reversible. This means that they are able to detach from the enzyme to facilitate usual catabolism of the substrate.[citation needed]



Specific foods with high amounts of tyramine:[2]

  • Aged cheese (gouda, camembert, cheddar)
  • Aged, smoked or pickled meats
  • Aged or fermented soy and yeast products (soy sauce, teriyaki sauce, home baked yeast bread, sourdough bread)
  • Overripe fruits
  • High amounts of nuts

Psychoactive substances

The MAOIs are well-known for their numerous drug interactions, including the following kinds of substances:

  • Substances that are metabolized by monoamine oxidase, as they can be boosted by up to several-fold
  • Substances that increase serotonin, noradrenaline, or dopamine activity as too much of any of these neurotransmitters can result in severe acute consequences including serotonin syndrome, hypertensive crisis, and psychosis.

By chemicals

  • Cholinergics, examples: alpha-GPC, choline bitartrate, citicoline
  • Lysergamides
  • Substituted phenethylamines
  • Releasing agents
    • Dopamine releasing agent (DRA)
    • Monoamine releasing agent (MRA) (or monoamine releaser)
    • Norepinephrine releasing agent (NRA) (or adrenergic releasing agent)
    • Norepinephrine-dopamine releasing agents (NDRAs)
    • Selective serotonin releasing agent (SSRA)
    • Serotonin releasing agent (SRA), and selective serotonin releasing agent (SSRA)
    • Serotonin–norepinephrine-dopamine releasing agent (SNDRA) (also known as a triple releasing agent (TRA))
  • Reuptake inhibitors
    • Dopamine reuptake inhibitors (DRI)
    • Monoamine reuptake inhibitors (MRIs)
    • Norepinephrine reuptake inhibitor (NRI, NERI) (or adrenergic reuptake inhibitor (ARI))
    • Norepinephrine-dopamine reuptake inhibitors (NDRI)
    • Serotonin reuptake inhibitor (SRA)
    • Selective serotonin reuptake inhibitors (SSRI)
    • Serotonin–norepinephrine–dopamine reuptake inhibitor (SNDRI), also known as a triple reuptake inhibitor (TRI)
      • Example: St. Johnswort (Hypericum perforatum)
  • Tetracyclic antidepressants (TeCA)
  • Tricyclic antidepressants (TCA)
  • Tryptamines

By pharmacolotherapy

  • Antibiotics
    • Linezolid
  • Local and general anesthetic


Nonselective MAO-A and MAO-B inhibitors

  • Naturally occurring sources
    • Coffee: MAO A inhibitors (harman and norharman) and MAO B inhibitor (norharman)[3]
    • Myristicin (weak) found in nutmeg (Myristica fragrans)
    • Passionflower (Passiflora incarnata): Harmaline and harmine are both nonselective MAO-A and MAO-B inhibitors. Passionflower also contains flavonoids that are MAO inhibitors, including apigenin, kaempferol and quercetin.
    • Syrian rue (Peganum harmala): Harmaline and harmine are both nonselective MAO-A and MAO-B inhibitors
    • Turmeric (Curcuma longa). Curcumin is commonly sold with piperine that enhances the effect of MAO inhibition.
  • Pharmaceuticals
    • Hydrazine (antidepressant)
      • Isocarboxazid (Marplan)
      • Nialamide (Niamid)
      • Phenelzine (Nardil, Nardelzine)
      • Hydracarbazine
    • Non-hydrazines
      • Tranylcypromine (Parnate, Jatrosom)

Selective MAO-A inhibitors

  • Psychedelics
  • Pharmaceuticals
    • Bifemelane (Alnert, Celeport) (available in Japan)
    • Isocarboxazid (common brand name Marplan)
    • Moclobemide (Aurorix, Manerix)
    • Phenelzine (common brand name Nardil)
    • Pirlindole (Pirazidol) (available in Russia)
    • Toloxatone (Humoryl) (available in France)
    • Tranylcypromine (common brand name Parnate)

Selective MAO-B inhibitors

  • Naturally occurring sources
    • Kavalactones found in Kava (Piper methysticum)
  • Pharmaceuticals
    • Rasagiline (Azilect)
    • Selegiline (Deprenyl, Eldepryl, Emsam, Zelapar)
    • Safinamide (Xadago)

See also

External links


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  1. Cristancho, Mario. "Atypical Depression in the 21st Century: Diagnostic and Treatment Issues". Psychiatric Times. Retrieved 23 November 2013.
  2. McCabe-Sellers BJ, Staggs CG, and Bogle ML. Tyramine in foods and monoamine oxidase inhibitor drugs: A crossroad where medicine, nutrition, pharmacy and food industry converge; J Food Comp Anal. 2006; 19:S58. |
  4. 4.0 4.1