What Are MAO Inhibitors?

Medically reviewed by Alan Carter, PharmD on September 5, 2017Written by Brian Krans on December 10, 2013

What are MAOIs?

Monoamine oxidase inhibitors (MAOIs) are a class of medication used to treat depression. They were introduced in the 1950s as the first drugs for depression. Today, they’re less popular than other depression medications, but some people benefit from their use.

Read on to learn more about MAOIs, including how they work, who they might help, and what foods to avoid while taking them.

How do MAOIs work?

MAOIs work with the chemicals in your brain called neurotransmitters that allow brain cells to communicate with each other. Depression is thought to be caused by low levels of the neurotransmitters dopamine, serotonin, and norepinephrine, which collectively are called monoamines. A chemical found naturally in the body, monoamine oxidase, removes these neurotransmitters.

By inhibiting monoamine oxidase, MAOIs allow more of these neurotransmitters to remain in the brain, thus elevating mood through improved brain cell communication.

Understanding monoamine oxidase

Monoamine oxidase is a type of enzyme that helps neurons fire throughout your body. It’s formed in your liver and cleans up neurotransmitters in your brain once they’ve done their jobs.

Besides neurotransmitters, monoamine oxidase cleans out tyramine, a chemical that helps regulate blood pressure. Because MAOIs inhibit monoamine oxidase from doing its job, they adversely affect blood pressure in addition to keeping neurotransmitters at optimal levels. People taking MAOIs have to pay special attention to their blood pressure, including avoiding certain foods.

Tyramine and foods to avoid

One downside to MAOIs is that they come with dietary restrictions because of the elevated tyramine levels in the blood.

When this class of drug first entered the market, no one knew about the concerns over tyramine and blood pressure. This caused a wave of deaths that prompted further research. Now we know that certain foods contain excess tyramine, and these should be avoided when taking MAOIs.

The more food ages, the more concentrated the levels of tyramine become. This is true for aged meats, cheeses, and even leftovers in your fridge. Foods with dangerously high levels of tyramine include:

  • soy sauce and other fermented soy products
  • sauerkraut
  • salami and other aged or cured meats

Other foods that contain high levels of tyramine are:

  • aged cheeses, such as Brie, cheddar, Gouda, Parmesan, Swiss, and blue cheese
  • alcohol, especially chianti, vermouth, and beers
  • fava beans
  • raisins, dates, and other dried fruits
  • tofu
  • all nuts

Get more information about tyramine-free diets.

Other precautions

Besides blood pressure problems, people taking MAOIs should also beware of a condition called serotonin syndrome. Symptoms can include:

The condition can manifest if a person on MAOIs takes other antidepressants or the herbal supplement St. John’s wort.

To avoid serotonin syndrome, people taking MAOIs shouldn’t take anything for two weeks when ending MAOI treatment and starting another.

Types of MAOIs

These days, MAOIs are rarely the first choice of prescription medication to treat depression. However, the U.S. Food and Drug Administration (FDA) — the regulating agency of all prescription medication — has approved the following MAOIs:

  • isocarboxazid (Marplan): can take three to six weeks to fully take effect
  • phenelzine (Nardil): can take up to four weeks to fully work
  • tranylcypromine (Parnate): can take up to 3 weeks to achieve its desired effects

Selegiline

Selegiline (Emsam, Atapryl, Carbex, Eldepryl, Zelapar) is a newer type of MAOI. It works by selectively blocking monoamine oxidase B (MAO-B). This reduces the breakdown of dopamine and phenethylamine and means there are no dietary restrictions. It’s available in patch form. Learn about other medications used to treat depression.

Aside from depression, selegiline is also prescribed for early onset Parkinson’s disease and dementia.

Side effects of MAOIs

MAOIs carry more side effects than other antidepressants, which is why they’re often the last drug prescribed to treat depression. Some side effects of MAOIs include:

MAOIs and suicide risk

The FDA requires a warning on antidepressants that they may increase the risk of suicide in children and young adults. While MAOIs are rarely prescribed for children, all people beginning any kind of antidepressant therapy should be watched for changes in mood, mindset, or attitude. Successful antidepressant treatments should lower suicide risk by increasing mood.

However, you should consult your doctor before you stop taking MAOIs or any other prescribed medication.

The takeaway

MAOIs are only one type of medication used to treat depression. Like most antidepressants, they may not be right for everyone and take weeks of use to reach their full effect. However, when used in combination with other therapies and lifestyle changes, they can be highly effective at combating depression symptoms. Talk to your doctor for more information to see if MAOI therapy suits your lifestyle.

CMS Id: 131276