An enzyme called monoamine oxidase is involved in removing the neurotransmitters norepinephrine, serotonin and dopamine from the brain. MAOIs prevent this from happening, which makes more of these brain chemicals available to effect changes in both cells and circuits that have been impacted by depression.

How do MAO inhibitors work?

MAO-B inhibitors decrease the normal activity of an enzyme -- monoamine oxidase -- that breaks down dopamine after it completes its activity in the brain. These drugs allow available dopamine (made by remaining dopamine-producing cells or given via other medications) to function for a longer period of time.

Does MAOI increase serotonin?

Monoamine oxidase inhibitors (MAOIs) are considered perhaps the most effective antidepressant agents in the psychiatrist's medical arsenal. They work by inhibiting the enzyme monoamine oxidase in the brain, thereby increasing levels of norepinephrine, dopamine and serotonin.