Monoamine oxidase inhibitors (MAOIs) were the first class of antidepressant to be introduced. Today, these drugs are still used, but much less frequently than in the past due to their potential to cause a dangerous spike in blood pressure (hypertensive crisis) when taken with certain types of foods, beverages and medications. Therefore, they are usually prescribed only if newer, safer antidepressants, such as selective serotonin reuptake inhibitors,  fail to relieve a patient’s symptoms.

MAOIs work by blocking monoamine oxidase, an enzyme (protein that catalyzes specific biochemical reactions) in the cells of most tissues that metabolizes neurotransmitters such as dopamine, norepinephrine and serotonin. By blocking this action, the neurotransmitters remain at high levels in the brain, which is believed to boost a person’s mood.

In addition to treating depression, MAOIs may also be prescribed for patients with conditions such as agoraphobia and social anxiety disorder.

Most MAOIs are available in tablet form. However, the U.S. Food and Drug Administration (FDA) recently approved an MAOI in the form of a skin patch (applied daily) for the treatment of depression.   

Individuals who take MAOIs must adhere closely to a medication and diet regimen that will reduce the risk of drug interactions and an adverse hypertensive reaction.

MAOIs are not typically prescribed for children or adults over the age of 60. Women who are pregnant or thinking about becoming pregnant should consult their physician before taking these drugs as studies have indicated that MAOIs may cause birth defects.