Monoamine Oxidase Inhibitors; Types, Mechanism, Uses, Side Effects, Interactions

Monoamine Oxidase Inhibitors; Types, Mechanism, Uses, Side Effects, Interactions

Monoamine oxidase inhibitors (MAOIs) are a class of drugs that inhibit the activity of one or both monoamine oxidase enzymes, monoamine oxidase A (MAO-A) and monoamine oxidase B (MAO-B). They have a long history of use as medications prescribed for the treatment of depression. They are particularly effective in treating atypical depression. They are also used in the treatment of Parkinson’s disease and several other disorders.

Reversible inhibitors of monoamine oxidase A (RIMAs) are a subclass of MAOIs that selectively and reversibly inhibit the MAO-A enzyme. RIMAs are used clinically in the treatment of depression and dysthymia, though they have not gained widespread market share in the United States. Because of their reversibility and selectivity, RIMAs are safer than the older MAOIs like phenelzine and tranylcypromine.

Types of Monoamine Oxidase Inhibitor

Marketed MAOIs

Nonselective MAO-A/MAO-B inhibitors

Hydrazine (antidepressant)

  • Isocarboxazid
  • Nialamide
  • Phenelzine
  • Hydracarbazine
  • Non-hydrazines
  • Tranylcypromine

Selective MAO-A inhibitors

  • Bifemelane
  • Moclobemide
  • Pirlindole
  • Toloxatone

Selective MAO-B inhibitors

  • Rasagiline
  • Selegiline
  • Safinamide

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

Methylene blue, the antidote indicated for drug-induced methemoglobinemia, among a plethora of other off-label uses, is a highly potent, reversible MAO inhibitor.

Mechanism of action of Monoamine Oxidase Inhibitor

Although the mechanisms for MAOIs beneficial action in the treatment of Parkinson’s disease are not fully understood, the selective, irreversible inhibition of monoamine oxidase type B (MAO-B) is thought to be of primary importance. MAO-B is involved in the oxidative deamination of dopamine in the brain. MAOIs binds to MAO-B within the nigrostriatal pathways in the central nervous system, thus blocking microsomal metabolism of dopamine and enhancing the dopaminergic activity in the substantial nigra. MAOIs may also increase dopaminergic activity through mechanisms other than inhibition of MAO-B. At higher doses, MAOIs can also inhibit monoamine oxidase type A (MAO-A), allowing it to be used for the treatment of depression.

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Indications of Monoamine Oxidase Inhibitors

Newer MAOIs (typically used in the treatment of Parkinson’s disease) and the reversible MAOI moclobemide provide a safer alternative and are now sometimes used as first-line therapy.

Contra-Indications of Monoamine Oxidase Inhibitors

Side Effects of Monoamine Oxidase Inhibitors

The most common 

More common

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Drug Interactions of Monoamine Oxidase Inhibitor

MAO inhibitors may interact with the following drug, supplements, & may change the efficacy of drugs

MAOIs that have been withdrawn from the market

  • Nonselective MAO-A/MAO-B inhibitors
    • Hydrazines
      • Benmoxin
      • Iproclozide
      • Iproniazid
      • Mebanazine
      • Octamoxin
      • Pheniprazine
      • Phenoxypropazine
      • Pivalylbenzhydrazine
      • Safrazine
    • Non-hydrazines
      • Caroxazone
  • Selective MAO-A inhibitors
    • Minaprine

List of RIMAs

Marketed pharmaceuticals

  • Brofaromine
  • Caroxazone
  • Eprobemide 
  • Methylene blue
  • Metralindole
  • Minaprine
  • Moclobemide
  • Pirlindole
  • Toloxatone



  2. PubChem

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