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What are monoamine oxidase inhibitors (MAOIs)?
MAOIs were the first class of antidepressants to be developed. They fell out of favor because of concerns about interactions with certain foods and numerous drug interactions. MAOIs elevate the levels of norepinephrine, serotonin, and dopamine by inhibiting an enzyme called monoamine oxidase. Monoamine oxidase breaks down norepinephrine, serotonin, and dopamine. When monoamine oxidase is inhibited, norepinephrine, serotonin, and dopamine are not broken down, increasing the concentration of all three neurotransmitters in the brain.
Monoamine oxidase also breaks down tyramine, a chemical present in aged cheese, wines, and other aged foods. Since MAOIs inhibit monoamine oxidase they decrease the break down of tyramine from ingested food, increasing the level of tyramine in the body. Excessive tyramine can elevate blood pressure and cause a hypertensive crisis. Patients treated with MAOIs should adhere to recommended dietary modifications that reduce the intake of tyramine. Interestingly, the 6 mg/24 hour dose of selegiline transdermal system (EMSAM) does not require dietary restrictions because at this dose EMSAM does not substantially inhibit tyramine. Higher selegiline transdermal system (EMSAM) doses require dietary restrictions.
MAOIs are associated with several significant drug interactions; limiting their usefulness in patients who are treated with multiple drugs. MAOIs interact with drugs that increase serotonin activity in the brain, increase norepinephrine, constrict blood vessels, or inhibit monoamine oxidase. Drugs that increase serotonin in the brain include:
Medically Reviewed by a Doctor on 5/31/2013
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