Monoamine oxidase inhibitor

Monoamine oxidase

Monoamine oxidase inhibitors (MAOIs) and reversible monoamine oxidase inhibitors (RIMAs) are a type of prescription antidepressant drug far less prescribed now than in the past. When they are used, it is most often for the treatment of atypical depression. MAOIs are sometimes used for Parkinson's disease, anxiety disorders, and social phobia, as well.

Since MAOIs drugs can be fatal if someone eats the wrong sorts of foods or beverages with them, and it is possible to die of an overdose of MAO inhibitors, MAOIs are usually only ever given when other antidepressant drugs have failed. Some newer drugs such as selegiline and moclobemide have proven to be safer than the older MAOIs.

Uses

MAOIs and RIMAs are used to provide a second line of treatment for certain psychiatric illnesses, most commonly types of hard to treat depression, and anxiety disorders (with or without panic attacks). They may also be used for social phobia. MAO-B inhibitors are used to treat Parkinson's disease. Certain MAOIs have been shown to help people to stop smoking tobacco, although they are rarely used for this.

How they work

Monoamine oxidase inhibitors work by stopping the action of an enzyme called monoamine oxidase. This enzyme breaks down a group of brain signalling chemicals called the monoamine neurotransmitters. There are two types of the enzyme, MAO-A and MAO-B. Each type breaks apart different chemicals in the group. MAO-A breaks down melatonin, serotonin, epinephrine and norepinephrine. MAO-B breaks down phenylethylamine and the trace amines. These chemicals (neurotransmitters) are used in the brain for signalling purposes. Dopamine, for example, is a type of neurotransmitter that affects motivation and pleasure.

Side effects

Like all drugs, MAOIs and RIMAs can have effects that are not intended and are not part of the treatment that the drugs provide. In this class of drug, these include a risk of a hypertensive crisis. This can be caused by high levels of tyramine; such as by eating cheese (except cream or cottage cheese, meat extracts such as Bovril, yeast extract, broth cubes, fermented soya bean products, alcohol (especially fortified wine (port, sherry), beer and chianti wine. Also preserved fish, preserved poultry, offal, avocado, banana skins, broad bean pods and pickled or smoked herring must be avoided. Certain medications can also cause a hypertensive crisis with MAOIs and RIMAs, such as; amphetamine, fenfluramine, ephedrine, phenlyephrine, phenylpropanolamine, nasal decongestants, L-dopa, pethidine and tricyclic antidepressants. Use of a RIMA rather than a MAOI can reduce these side-effects, however foods with significant amounts of tyramine should still be avoided.

List of MAO inhibiting drugs

Marketed MAOIs

Linezolid is an antibiotic drug with weak, reversible MAO-inhibiting activity.

The antibiotic furazolidone also has MAO-inhibiting activity

Methylene blue (methylthioninium chloride), the antidote indicated for drug-induced methemoglobinemia on the World Health Organization's List of Essential Medicines, among a plethora of other off-label uses, is a highly potent, reversible MAO inhibitor.

The Food and Drug Administration (FDA) has approved these MAOIs to treat depression:

MAOIs that have been withdrawn from the market

List of RIMAs

Marketed pharmaceuticals

Other pharmaceuticals

Naturally occurring RIMAs in plants

Only reversible phytochemical MAOIs have been characterized.

Research compounds

Notes

  1. ↑ Lawrence KR, Adra M, Gillman PK (June 2006). "Serotonin toxicity associated with the use of linezolid: a review of postmarketing data". Clinical Infectious Diseases. 42 (11): 1578–83. doi:10.1086/503839. PMID 16652315.
  2. ↑ A.M. Timperio; H.A. Kuiper & L. Zolla (February 2003). "Identification of a furazolidone metabolite responsible for the inhibition of amino oxidases". Xenobiotica. 33 (2): 153–167. doi:10.1080/0049825021000038459. PMID 12623758. S2CID 35868007.
  3. ↑ Petzer A, Harvey BH, Wegener G, Petzer JP (February 2012). "Azure B, a metabolite of methylene blue, is a high-potency, reversible inhibitor of monoamine oxidase". Toxicology and Applied Pharmacology. 258 (3): 403–9. Bibcode:2012ToxAP.258..403P. doi:10.1016/j.taap.2011.12.005. PMID 22197611.
  4. ↑ "An option if other antidepressants haven't helped". Mayo Clinic. Retrieved 2021-12-09.
  5. ↑ Donskaya NS, Antonkina OA, Glukhan EN, Smirnov SK (1 July 2004). "Antidepressant Befol Synthesized Via Interaction of 4-Chloro-N-(3-chloropropyl)benzamide with Morpholine". Pharmaceutical Chemistry Journal. 0091-150X. 38 (7): 381–384. doi:10.1023/B:PHAC.0000048439.38383.5f. S2CID 29121452.
  6. ↑ Chaurasiya, Narayan D.; Leon, Francisco; Muhammad, Ilias; Tekwani, Babu L. (2022-07-04). "Natural Products Inhibitors of Monoamine Oxidases—Potential New Drug Leads for Neuroprotection, Neurological Disorders, and Neuroblastoma". Molecules. 27 (13): 4297. doi:10.3390/molecules27134297. ISSN 1420-3049. PMC 9268457. PMID 35807542.
  7. ↑ van Diermen, Daphne; Marston, Andrew; Bravo, Juan; Reist, Marianne; Carrupt, Pierre-Alain; Hostettmann, Kurt (2009-03-18). "Monoamine oxidase inhibition by Rhodiola rosea L. roots". Journal of Ethnopharmacology. 122 (2): 397–401. doi:10.1016/j.jep.2009.01.007. ISSN 0378-8741. PMID 19168123.

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