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Monoamine Oxidase Inhibitors (MAOI)

Monoamine oxidase enzymes serve to break down various important neurotransmitters in the body's nervous system, such as serotonin, dopamine and norepinephrine. Monoamine oxidase A (MAO-A) breaks down serotonin and norepinephrine (as well as melatonin and tyramine), while monoamine oxidase B (MAO-B) breaks down mainly dopamine. It is thought that having low levels of these various neurotransmitters can lead to Depression.

Monoamine Oxidase Inhibitors (MAOIs) are a group of medications that block the actions of the monoamine oxidase enzymes and thus boost the levels of serotonin, dopamine and norepinephrine acting in the brain. In this way they are used as antidepressants to help relieve the symptoms of Depression.

There are various MAOIs that have been developed. Isocarboxazid (Marplan), Phenelzine (Nardil) and Tranylcypromine (Parnate) block both MAO-A and MOA-B. Moclobemide (Aurorix, Manerix) blocksonly MAO-A. Selegiline (Emsam) blocks only MAO-B, and is used mainly for treatingParkinson's Disease.

The MAOIs are not the first choice antidepressants these days because they are quite difficult to use. People taking these medications must avoid all foods that contain tyramine. This includes, but is not limited to: aged cheeses; avocados; overripe fruits and vegetables; aged, cured, pickled or processed meats and liver; wine; soy products; and various kinds of nuts. People who eat these foods when also taking an MAOI can have a dangerous and potentially life-threatening reaction that can include very high blood pressure, stroke, and heart attack.

For this same reason, MAOIs must not be combined with other medications that increase levels of serotonin, norepinephrine or dopamine. This includes, but is not limited to, all other antidepressants, stimulants, and Atypical Antipsychotics.

Most of the MAOIs deactivate the monoamine oxidase enzymes for up to two weeks after use, which means that the above dietary and medication restrictions need to be kept for 2 weeks after the MAOI has been stopped.

Moclobemide (Aurorix, Manerix) is considered a reversible MAOI because soon after it is discontinued its effects on the monoamine oxidase enzymes cease. For this reason, it is much better tolerated than the other MAOIs. The above dietary restrictions need not be held as strictly, for foods containing tyramine may cause an elevation in blood pressure when Moclobemide is being used, but not in a way that is likely to be serious or life-threatening. On the other hand, Moclobemide should still not be combined with medications like antidepressants, stimulants, and Atypical Antipsychotics that can increase serotonin and norepinephrine levels.