MAOI (monoamine oxidase inhibitor) Antidepressants

Monamine oxidase inhibitors were the first medications marketed as antidepressants. They were developed in the 1940's and are still in use. They have been largely supplanted by other antidepressants that have fewer side effects, but there are still some situations where a MAOI is indicated. They are used to treat:

MAOIs are also used to treat panic disorder and other conditions.

How MAOIs work

Depression is thought to be related to an imbalance of brain chemicals, especially serotonin, dopamine and norepinephrine. These chemicals carry messages between nerve cells. They are released into the space between two nerve cells, and they bind with specific sites on the cell membrane of the receiving cell. Any chemicals that don't bind with the receiving cell are broken down and returned to the first cell by an enzyme called monamine oxidase.

MAOIs inhibit monamine oxidase and keep it from breaking down the chemicals. That allows them to accumulate and helps restore the chemical balance.


Monamine oxidase inhibitors should not be taken if:

Side Effects

Most people have side effects when they are taking MAOIs. The side effects are usually mild and temporary, but they can be serious enough to warrant stopping the medication. The usual side effects of MAOIs are:

The most serious side effects of MAOIs are related to their potential for interaction with food and other medications. These are discussed in the next section.


MAOIs interact with a wide range of foods, supplements and medications. Some of them are:

Hypertensive crisis: Tyramine and MAOIs can produce a hypertensive crisis, where your blood pressure rises rapidly and becomes very high. This can result in a heart attack or stroke, and is a medical emergency.

Serotonin syndrome: MAOIs interact with other antidepressants and serotonergic medications because they both alter serotonin levels. A toxic reaction, serotonin syndrome, can occur. This is sometimes described as Neuroleptic Malignant Syndrome or as MAOI reaction. Characteristics include shaking and shivers, anxiety, tremors and sweating and can progress to very high fevers, seizures, cardiovascular collapse and death.


As with other antidepressants, MAOIs must be withdrawn gradually. Abruptly stopping them can cause withdrawal symptoms that can be extremely uncomfortable.

Appendix 1: Tyramine-containing foods

Tyramine is found primarily in aged or fermented foods. The tyramine content rises as the food ages-something that has been in the refrigerator for a week has more tyramine than it did when it was fresh. One way to avoid tyramine is to eat very fresh foods.

Cheese and wine have more tyramine than other foods. Here is a list of other tyramine-containing foods.