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Monoamine oxidase inhibitors were the first class of medications to be categorized as antidepressants. The current use of these agents is primarily limited to treating atypical and refractory cases of depression. The development of newer antidepressants with a more favorable side effect profile, less overdose toxicity, and no dietary restrictions (see Chapter 172, Atypical Antidepressants, Serotonin Reuptake Inhibitors, and Serotonin Syndrome) has eliminated much of the need for these agents. Nonetheless, it still remains important that emergency physicians continue their familiarity with monoamine oxidase inhibitors, because they are associated with tyramine reactions, serotonin syndrome, and certain medication incompatibilities that are unique to this class of antidepressants. Intentional overdoses of monoamine oxidase inhibitors are considered life-threatening emergencies due to the complex and severe symptoms typically seen with these types of ingestions. The onset of clinical toxicity is often delayed to between 6 and 24 hours after ingestion, which can lead to misdiagnosis and mismanagement.


Monoamine oxidase inhibitor exposures are commonly combined with exposures to other drugs, occur mostly in adults, and have a high frequency of serious clinical effects.1,2 The declining popularity of monoamine oxidase inhibitors for the treatment of depression is partially offset by the increasing use of specific agents in this class for the treatment of Parkinson’s disease. Also, a transdermal method of selegiline administration has been approved for use in major depression and appears to avoid some of the worrisome aspects associated with traditional oral therapy.3 The U.S. Food and Drug Administration has approved four monoamine oxidase inhibitors for use in treating major depression and two for use in treating Parkinson’s disease (Table 173-1).4 The safety and effectiveness of these agents in the pediatric population has not been established, and the four agents used for treatment of depression have the identical U.S. Food and Drug Administration–mandated black box warning that patients <24 years of age may have increased suicidal thinking and behavior while taking any type of antidepressant medication.

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Table 173-1 U.S. Food and Drug Administration–Approved Monoamine Oxidase Inhibitors

Monoamine oxidase inhibitor antidepressants with improved safety and tolerability are available only outside the U.S. The most popular of these newer inhibitors is moclobemide, which is widely available in Canada and Europe. ...

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