Monoamine oxidase inhibitors (MAOIs)

MAOIs were the first type of antidepressant developed. Learn about the benefits, side effects and risks of these 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 They're effective, but they've generally been replaced by antidepressants that are safer and cause fewer side effects.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 ultimately effecting changes in the brain chemistry that are operational in depression.

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 to effect changes in both cells and circuits that have been impacted by depression.

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 MAOIs 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
  • Dizziness or lightheadedness
  • Skin reaction at the patch site

Other possible side effects include:

  • Involuntary muscle jerks
  • Low blood pressure
  • Reduced sexual desire or difficulty reaching orgasm
  • Weight gain
  • Difficulty starting a urine flow
  • Muscle cramps
  • Prickling or tingling sensation in the skin (paresthesia)
June 08, 2016 See more In-depth