MAO inhibitor

MAO inhibitors or Monoamine oxidase inhibitors 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.

History

The discovery of the effect of monoamine oxidase inhibitors on depression was a chance finding. Iproniazid, originally developed for tuberculosis, was found to have psychoactive properties. Subsequent research showed that it was a potent MAO inhibitor, leading to its development as the first antidepressant.

Mechanism of action

MAO inhibitors act by inhibiting the activity of monoamine oxidase, thus 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, epinephrine, and norepinephrine. MAO-B preferentially deaminates phenethylamine and certain other trace amines; in contrast, MAO-A preferentially deaminates other trace amines, like tyramine, whereas dopamine is equally deaminated by both types.

Uses

MAO inhibitors are used in the treatment of depression and anxiety. They are also used in the treatment of Parkinson's disease and several other disorders. The use of MAO inhibitors has declined due to the introduction of newer antidepressants which have fewer side effects.

Side effects

The most common side effects of MAO inhibitors include dry mouth, nausea, diarrhea, constipation, and dizziness. More serious side effects may include high blood pressure, liver damage, and serotonin syndrome.

See also

• Antidepressant
• Depression
• Parkinson's disease

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