Monoamine oxidase inhibitors (MAOIs)

MAOIs — Learn about the benefits, side effects and risks of these older antidepressants. By Mayo Clinic Staff

Monoamine oxidase inhibitors (MAOIs) were the first type of antidepressant developed. They're effective, but they've generally been replaced by antidepressants that are safer and cause fewer side effects.

Use of MAOIs typically requires diet restrictions because they can cause dangerously high blood pressure when taken with certain foods or medications. In spite of side effects, these medications are still a good option for some people. In certain cases, they relieve depression when other treatments have failed.

How MAOIs work

Antidepressants such as MAOIs ease depression by affecting chemical messengers (neurotransmitters) used to communicate between brain cells. Like most antidepressants, MAOIs work by changing the levels of one or more of these naturally occurring brain chemicals.

An enzyme called monoamine oxidase is involved in removing the neurotransmitters norepinephrine, serotonin and dopamine from the brain. MAOIs prevent this from happening, which makes more of these brain chemicals available. This is thought to boost mood by improving brain cell communication.

MAOIs also affect other neurotransmitters in the brain and digestive system, causing side effects. MAOIs are sometimes used to treat conditions other than depression, such as Parkinson's disease.

MAOIs approved to treat depression

The Food and Drug Administration (FDA) has approved these MOAIs to treat depression:

  • Isocarboxazid (Marplan)
  • Phenelzine (Nardil)
  • Selegiline (Emsam)
  • Tranylcypromine (Parnate)

Selegiline is available as a skin (transdermal) patch. Using a patch may cause fewer side effects than MAOIs taken by mouth. If you're using the lowest dose patch, you may not need diet restrictions, but ask your doctor.

Side effects of MAOIs

Because of side effects and safety concerns, MAOIs are most often tried when other antidepressants don't work.

The most common side effects of MAOIs include:

  • Dry mouth
  • Nausea, diarrhea or constipation
  • Headache
  • Drowsiness
  • Insomnia
  • Skin reaction at the patch site
  • Dizziness or lightheadedness

Other possible side effects include:

  • Involuntary muscle jerks
  • Low blood pressure
  • Reduced sexual desire or difficulty reaching orgasm
  • Sleep disturbances
  • Weight gain
  • Difficulty starting a urine flow
  • Muscle aches
  • Prickling or tingling sensation in the skin (paresthesia)
Jun. 21, 2013 See more In-depth