Monoamine Oxidase Inhibitors (MAOIs)

Medically Reviewed by Jennifer Casarella, MD on August 28, 2022
3 min read

Monoamine oxidase inhibitors (MAOIs) are an extremely strong class of antidepressants that treat depression by preventing the breakdown of the brain chemicals serotonin, dopamine, and norepinephrine. This helps them do their work of regulating your mood.

These medications aren’t used often because there’s a risk they’ll change the way other drugs you’re taking work. This could lead to blood pressure issues and other problems. Also, an overdose of these drugs can be especially dangerous.

MAOIs approved by the FDA to treat bipolar depression include:

Like other classes of antidepressants, MAOIs take several weeks to begin working. Your doctor may also prescribe a sedative to help relieve anxiety, agitation, or sleep problems while the antidepressant begins to work. You will also need to monitor what foods you eat to avoid side effects.

Selegiline (Emsam ), a newer MAOI, works by blocking monoamine oxidase B (MAOI-B). It gets into your body through a patch that you wear on your skin.

Monoamine oxidase inhibitors (MAOIs) change the levels of the brain chemicals norepinephrine, serotonin and dopamine called neurotransmitters. Known as neurotransmitters, their job is to keep your mood stable. An enzyme called monoamine oxidase helps to remove them from your brain. MAOIs stop that enzyme from being able to work as it usually does, which leaves higher levels of neurotransmitters in your brain where they can work on cells that are affected by depression.

Common side effects of MAOIs may include:

  • Sleepiness, or trouble getting to sleep
  • Dizziness, lightheadedness, and fainting
  • Dry mouth, blurred vision, and appetite changes
  • High or low blood pressure
  • Changes in heart rate and rhythm
  • Muscle twitching or cramps, feelings of restlessness, or a pins-and-needles feeling in your skin
  • Weight gain
  • Stomach issues such as nausea, diarrhea or constipation
  • Skin irritation where patches are used
  • Loss of sex drive or ability, or having a hard time reaching orgasm
  • Headaches

These medications can cause other problems such as:

  • Food interactions. Eating certain smoked, fermented, or pickled foods or drinking certain beverages can cause severe, sudden high blood pressure in combination with MAOIs. People taking these antidepressants must follow a special diet that includes limiting certain cheeses, meats, and alcohol. In addition, some experts think that MAOIs may be especially likely to cause mood switches from depression to mania in people with bipolar disorder, and therefore, mood changes must be monitored closely.
  • Drug interactions. As with eating certain foods, taking certain medications can also cause dangerous and sudden high blood pressure when they are taken at the same time as MAOIs. This includes other antidepressants, pain medications, and cold and allergy medications. It’s important to tell your doctor or pharmacist about any medications you are taking, including herbal supplements, if you are prescribed an MAOI.
  • Serotonin syndrome. A rare side effect of MAOIs is having a dangerously high level of the neurotransmitter serotonin. This can happen when you take two medications that raise your serotonin levels at the same time (like other antidepressants, some pain medications, migraine treatments, or St. John’s wort). It’s rare, but it can be life-threatening. Seek immediate medical help if you experience symptoms of serotonin syndrome, like:
    • Feeling agitated or restless
    • A fast heartbeat or high blood pressure
    • Diarrhea, nausea or vomiting
    • Hallucinations (seeing things that are not real)
    • Fever or a higher body temperature
    • Loss of muscle control or coordination
    • Abnormal eye movements
    • Sweating
    • Overactive reflexes
  • Suicide risk. The FDA requires all antidepressants, including MAOIs, to carry a warning that there’s a small risk they could make you more likely to attempt suicide. This risk is highest when you’ve just started taking MAOIs or the doctor recently changed your dosage.

The longer you’ve been taking an MAOI, the more likely you are to have these symptoms.

If you are pregnant

There’s little information on the safety of MAOIs during pregnancy. Talk to your doctor if you get pregnant while taking an MAOI or if you plan to become pregnant. Don’t stop taking any prescribed medication without letting your doctor know.

Stopping treatment

It’s important that you talk to your doctor before you decide to stop taking an MAOI. Stopping suddenly can cause withdrawal symptoms, which can be dangerous to your health, including:

  • Flu-like symptoms (sweating, chills, nausea)
  • Trouble sleeping
  • Agitation
  • Confusion
  • Psychosis