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Monoamine oxidase inhibitors (MAOIs)
MAOIs — Benefits, side effects and risks of these older antidepressants.
By Mayo Clinic staffMonoamine oxidase inhibitors (MAOIs) were the first type of antidepressant developed. They're effective, but have generally been replaced by antidepressants that are safer and cause fewer side effects. MAOIs generally require diet restrictions because they can cause dangerously high blood pressure when taken with certain foods. 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. Most antidepressants work by changing the levels of one or more of these naturally occurring brain chemicals.
The enzyme monoamine oxidase is involved in removing the neurotransmitters norepinephrine (nor-ep-ih-NEF-rin), serotonin (ser-oh-TOE-nin) and dopamine (DOE-puh-mene) 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.
Monoamine oxidase inhibitors approved to treat depression
MAOIs approved by the Food and Drug Administration to treat depression, with their generic names followed by available brand names in parentheses, include:
- Isocarboxazid (Marplan)
- Phenelzine (Nardil)
- Selegiline (Emsam, Eldepryl, Zelapar)
- Tranylcypromine (Parnate)
Selegiline is available as a skin (transdermal) patch. Using a patch may cause fewer side effects than may MAOIs taken orally. If you're using the lowest dose patch, you may not need diet restrictions.
MAOIs are sometimes used to treat conditions other than depression.
Side effects of monoamine oxidase inhibitors
Because of side effects and safety concerns, MAOIs are most often tried when other antidepressants don't work.
Side effects of MAOIs can include:
- Daytime sleepiness
- Dizziness or lightheadedness
- Low blood pressure
- Diarrhea
- Dry mouth
- Altered sense of taste
- Nervousness
- Muscle aches
- Insomnia
- Weight gain
- Reduced sexual desire or difficulty reaching orgasm
- Inability to maintain an erection (erectile dysfunction)
- Difficulty urinating
- Prickling or tingling sensation in the skin (paresthesia)
(1 of 2)
- Schatzberg AF, et al. Antidepressants: Introduction. In: Schatzberg AF, et al. Manual of Clinical Psychopharmacology. 7th ed. Arlington, Va.: American Psychiatric Publishing; 2010. http://www.psychiatryonline.com/content.aspx?aID=600624. Accessed Oct. 5, 2010.
- Fava M, et al. Antidepressants. In: Stern TA, et al. Massachusetts General Hospital Comprehensive Clinical Psychiatry. Philadelphia, Pa.: Mosby. 2008. http://www.mdconsult.com/das/book/body/221513496-3/0/1657/421.html?tocnode=57543329&fromURL=421.html#4-u1.0-B978-0-323-04743-2..50045-7_1104. Accessed Oct. 5, 2010.
- Hirsch M, et al. Antidepressant medication in adults: MAO inhibitors and others. http://www.uptodate.com/home/index.html. Accessed Oct. 7, 2010.
- Chew RH, et al. Monoamine oxidase inhibitors. In: Chew RH, et al. What your patients need to know about psychiatric medications. 2nd ed. Washington, DC.: American Psychiatric Publishing; 2009.
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