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Understanding Antidepressant Medications (cont.)

Monoamine Oxidase Inhibitors

Monoamine oxidase inhibitors (MAOIs) include isocarboxazid (Marplan), phenelzine (Nardil), and tranylcypromine (Parnate). These medications are rarely used because of strict dietary requirements and life-threatening drug and food interactions. Because of these drug and food interactions, MAOIs may not be taken with many other types of medicines, and some foods that are high in tyramine, dopamine, or tryptophan must be avoided as well.

How do MAOIs work?

These drugs inhibit monoamine oxidase. Monoamine oxidase is an enzyme in the body that is responsible for metabolizing (breaking down) neurotransmitters such as norepinephrine, epinephrine, dopamine, and serotonin. The result of MAOIs is an increase in the concentration of neurotransmitters. Some of these neurotransmitters increase blood pressure.

Who should not use these medications?

In many circumstances, the use of MAOIs is dangerous.

  • Individuals who are allergic to MAOIs
  • Individuals with diseases, such as pheochromocytoma or hypertension, that cause increased blood pressure
  • Individuals with diseases, such as heart failure or other heart disease, severe impaired renal function, and stroke or other cerebrovascular disease, in which increased blood pressure is likely to aggravate the condition
  • Individuals with a history of headache
  • Individuals with liver disease
  • Individuals using other drugs that may elevate blood pressure or cause additive effects (see drug interactions)
  • Individuals consuming foods with high tyramine content—MAOIs may lead to dangerously elevated blood pressure (see food interactions)
  • MAOIs are administered orally.
  • MAOIs are rarely the first antidepressant drug prescribed, but they are an option when initial treatments do not work or are not tolerated.
  • MAOIs are not a good choice for elderly or debilitated individuals.

Children: Phenelzine is not approved for children younger than 16 years. Tranylcypromine is not approved for children or adolescents.

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