Monoamine Oxidase Inhibitors (MAOIs)

Early Class of Drug Still Used to Treat Atypical Depression

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Monoamine oxidase inhibitors (MAOIs) were the first type of antidepressant developed in the early 1950s. While they have largely been supplanted by other classes of drug, MAOIs still have their place in treatment, most notably in persons diagnosed with atypical depression.

How MAOIs Work

Moods are largely regulated by chemicals in the brain called neurotransmitters. There are three types of neurotransmitter commonly involved in moods—serotonin, norepinephrine, and dopamine—all of which are classified as monoamines (meaning they contain one amino acid group).

Used neurotransmitters are commonly destroyed by an enzyme known as monoamine oxidase. However, if the process is too robust and too many neurotransmitters are destroyed, a person can develop neuropsychiatric symptoms in the form of depression.

MAOIs work by blocking the activity of this enzyme, resulting in higher levels of neurotransmitters and an improvement in depression symptoms.

MAOI antidepressants approved for use in the U.S. include:

  • Marplan (isocarboxazid)
  • Nardil (phenelzine)
  • Parnate (tranylcypromine)
  • Emsam - selegiline transdermal

While MAOIs are not commonly used in the first-line treatment of depression, they are particularly effective in cases of atypical depression. This is the form of depression characterized by overeating, excessive sleeping, sensitivity to rejection, and leaden paralysis (slowed movements due to a perceived heaviness in the legs and arms).

MAOIs are commonly used to treat Parkinson's disease and can also be used as an alternative prophylactic (preventive) treatment for severe migraines.

Why MAOIs Are Less Commonly Used

Today, depression is more commonly treated is with another class of drug called selective serotonin reuptake inhibitors (SSRIs) which include Zoloft (sertraline) and Paxil (paroxetine). This is due, in part, to the large number of side effects and drug interactions experienced by people on MAOIs.

One of the major concerns is the dietary restrictions by which persons on an MAOI need to avoid foods and beverages containing tyramine. These include liver and fermented food items such as cheeses and alcoholic beverages. Because tyramine affects blood pressure and MAOI increases tyramine, any addition to the diet can lead to a hypertensive crisis and possibly death.

MAOIs are also associated with withdrawal symptoms if treatment is ever stopped. While other antidepressants also have this side effect, it is considered particularly profound with MAOIs. As a result, a drug would need to be tapered off under the supervision of a doctor and accompanied by a treatment gap of anywhere from two to five weeks before a new antidepressant drug can be started.

Drug Interactions

One the major challenges of MAOIs is the wide range of drug interactions a person can experience during treatment. These include prescription and over-the-counter medications as well as street drugs. Unless properly managed, an MAOI can interfere with other treatments or even reduce the effectiveness of the MAOI itself.

The list of drug interactions include:

  • Amphetamines
  • Antihistamines
  • Antipsychotics
  • Asthma medications
  • Blood pressure medications
  • BuSpar (buspirone)
  • Cocaine
  • Demerol (pethidine)
  • Prozac (fluoxetine)
  • Ritalin (methylphenidate)
  • Tegretol (carbamazepine)
  • Tricyclic antidepressants
  • Tryptophan
  • Wellbutrin (bupropion)

It is, in fact, considered dangerous if an MAOI is taken with cocaine, Demerol, Prozac, or any tricyclic antidepressant. Generally speaking, MAOIs should never be used with any other type of antidepressant, including another MAOI.

A Word From Verywell

MAOIs, while less commonly used today than SSRIs, can be effective in specific, hard-to-treat cases. If prescribed an MAOI, it is important that you advise your doctor about any and all drugs you are taking, legal or otherwise.

Moreover, once treatment is started, you should never take any drug, including over-the-counter cold and fluid remedies, without first speaking with your doctor.

Source:

Grady, M. and Stahl, S. "Practical guide for prescribing MAOIs: debunking myths and removing barriers." CNS Spectrums 2012; 17:2-10. DOI: 10.1017/S109285291200003X.

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