MAOI - Side Effects, Diet, and Interactions
Wellness & SelfcareDrugs

What Is an MAOI?

By
Mathieu Rees
Updated on November 29, 2024
by

Monoamine oxidase inhibitors are antidepressants that affect the brain’s processing of neurotransmitters. As well as depression, these medications can treat social anxiety disorders, panic disorders, and bipolar disorder.

What Are Monoamine Oxidase Inhibitors (MAOIs)?

MAOIs are a type of antidepressant. They target monoamine oxidase, an enzyme that functions to break down certain neurotransmitters, called monoamines. Neurotransmitters are substances that send signals within the brain. For this reason, MAOIs can treat various mental health conditions. These include depression, anxiety, and bipolar disorder.

Appropriate treatment for mental health conditions is very important. Depression can lead to suicidal thoughts,

 while social anxiety can mean that people avoid important events.

 Bipolar disorder can cause serious dysfunction in people’s professional and personal lives.

MAOIs could help prevent or manage these symptoms.

What Conditions Do MAOIs Treat?

MAOIs can treat a variety of mental health conditions, like the following.

Depression

Depression is a mood disorder that can cause people to feel low, unmotivated, and tired. In some cases, people with depression also experience suicidal thoughts, which they may try to act on. Medications like MAOIs can improve these symptoms, although in some cases, these improvements begin only after several weeks of treatment.

Social Anxiety

Social anxiety disorder is when someone feels intense anxiety or fear in certain social settings. Social events, being at work, and public speaking are common triggers of social anxiety disorder. Some people with social anxiety disorder benefit from MAOIs.

Panic Disorders

Panic disorders cause people to have frequent and unexpected panic attacks. These attacks involve a sudden wave of fear, discomfort, or feeling of loss of control. There does not have to be a clear danger or trigger.

Bipolar Disorder

Bipolar disorder is when a person experiences unusual changes in their mood, energy levels, and concentration. They may spend stretches of time in a very depressed period, before becoming highly energized. These changes in mood can cause problems in a person’s day-to-day life. MAOIs are a drug that can be added to a regimen involving a mood stabilizer or an antipsychotic to help with depressive symptoms.

How Do MAOIs Work?

Laura Hack, MD, PhD, is an assistant professor of psychiatry and behavioral sciences at Stanford University in California. She explains that MAOIs “work by blocking enzymes that break down important mood-related chemicals in the brain — specifically serotonin, norepinephrine, and dopamine.” This causes higher levels of these monoamines.

For some time, scientists believed that low neurotransmitter levels were the only basis for depression. This is because “people often became depressed when given medications that depleted these chemicals, and when recovering patients had their serotonin levels artificially lowered, their depression frequently returned,” says Dr. Hack.

Scientists now think that depression is much more complicated than this. Hack states that “while MAOIs increase brain chemicals almost immediately, it typically takes several weeks before patients notice improvements in their mood.” This suggests that depression involves more than just low monoamine levels. More research is therefore needed to understand depression and its treatment with MAOIs.

Types of MAOIs

MAOIs are prescription medications. Doctors classify MAOIs into several types.

Enzyme Selectivity

There are two forms of monoamine oxidase, MAO-A and MAO-B. As Hack explains, some MAOIs are nonselective, meaning they affect both. Such MAOIs include:

  • phenelzine
  • tranylcypromine
  • isocarboxazid
Selective MAO-A inhibitors and selective MAO-B inhibitors affect only MAO-A and MAO-B, respectively. Moclobemide is a selective MAO-A inhibitor. Selegiline and rasagiline are selective MAO-B inhibitors.

Reversibility

Hack notes that some MAOIs form permanent bonds with MAO enzymes, inhibiting them for as long as they exist. These are irreversible MAOIs, which include phenelzine and tranylcypromine. By contrast, reversible inhibitors (RIMAs) like moclobemide bind to MAO enzymes only temporarily. Other medications can undo this bond, meaning that RIMAs are less likely to interact with other drugs.

Administration

Selegine is available as a tablet and as a skin patch. Other MAOIs are available only as tablets. These include:

  • isocarboxazid
  • phenelzine
  • tranylcypromine

What Are the Possible Side Effects of MAOIs?

Jonathan E. Alpert, MD, PhD, is the chair of the APA’s Council on Research and the Silverman University Chair in the department of psychiatry and behavioral sciences at Montefiore Medical Center and Albert Einstein College of Medicine in Bronx, New York. He says that “monoamines are ubiquitous in the brain and body and have myriad effects on multiple domains of function.” These include:

  • Appetite and metabolism
  • Blood pressure
  • Sexual function
  • Sleep

In addition, “MAO enzymes are found in both brain and gut and have important interactions with other medications (including other serotonin acting drugs and medications that affect constriction of blood vessels) as well as certain kinds of food (such as aged or fermented foods).” For these reasons, MAOIs can have many side effects.

Dr. Alpert lists the following:

  • Dangerously high blood pressure
  • Insomnia
  • Dizziness
  • Feeling agitated
  • Sexual dysfunction
  • Weight gain
  • Low blood pressure when getting up

Are There Any Risks Related to MAOIs?

MAOIs do carry certain risks.

 These include hypertensive crisis, which is when a person’s blood pressure spikes. Hypertensive crisis occurs when MAO-A inhibitors interact with sympathomimetic amines. These are substances that arise naturally in fermented foods like cheese. If you are going to take MAOIs, you should discuss diet with your doctor.

When combined with antidepressants or serotonin-altering medications, MAOIs can cause serotonin syndrome. This occurs when there is too much serotonin in a person’s body. Serotonin syndrome can cause the following symptoms:

  • Delirium
  • Changes in vital signs such as hypertension, tachycardia, and fever
  • Diarrhea
  • Tremors

If you are taking MAOIs and experience these symptoms, seek immediate medical advice. Without treatment, serotonin syndrome is a life-threatening condition.

The Takeaway

  • MAOIs affect certain enzymes inside the brain, causing higher levels of certain neurotransmitters.
  • These drugs can improve symptoms of mental health conditions, like depression and panic disorder.
  • They come with certain risks and side effects, which can be serious. Speak with your doctor to find out whether MAOIs are the right drug for you.
EDITORIAL SOURCES
Everyday Health follows strict sourcing guidelines to ensure the accuracy of its content, outlined in our editorial policy. We use only trustworthy sources, including peer-reviewed studies, board-certified medical experts, patients with lived experience, and information from top institutions.
Resources
  1. Sabri MA et al. MAO Inhibitors. StartPearls. June 2023.
  2. Depression. National Institute of Mental Health. March 2024.
  3. Social Anxiety Disorder: More Than Just Shyness. National Institute of Mental Health. 2022.
  4. Bipolar Disorder. National Institute of Mental Health. February 2024.
  5. Panic Disorder: When Fear Overwhelms. National Institute of Mental Health. 2022.
  6. Shih JC et al. Role of MAO A and B in neurotransmitter metabolism and behavior. Polish Journal of Pharmacology. 1999.
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Angela-Harper-bio

Angela D. Harper, MD

Medical Reviewer
Castle Connolly Top Doctor

Angela D. Harper, MD, is in private practice at Columbia Psychiatric Associates in South Carolina, where she provides evaluations, medication management, and psychotherapy for adults.  

A distinguished fellow of the American Psychiatric Association, Dr. Harper has worked as a psychiatrist throughout her career, serving a large number of patients in various settings, including a psychiatric hospital on the inpatient psychiatric and addiction units, a community mental health center, and a 350-bed nursing home and rehab facility. She has provided legal case consultation for a number of attorneys.

Harper graduated magna cum laude from Furman University with a bachelor's degree and cum laude from the University of South Carolina School of Medicine, where she also completed her residency in adult psychiatry. During residency, she won numerous awards, including the Laughlin Fellowship from the American College of Psychiatrists, the Ginsberg Fellowship from the American Association of Directors of Psychiatric Residency Training, and resident of the year and resident medical student teacher of the year. She was also the member-in-training trustee to the American Psychiatric Association board of trustees during her last two years of residency training.

Harper volunteered for a five-year term on her medical school's admission committee, has given numerous presentations, and has taught medical students and residents. She currently supervises a nurse practitioner. She is passionate about volunteering for the state medical board's medical disciplinary commission, on which she has served since 2015.

She and her husband are avid travelers and have been to over 55 countries and territories.

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Mathieu Rees

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