monoamine oxidase inhibitor (MAOI, MAO inhibitor), any of a chemically heterogeneous group of drugs used primarily in the treatment of depression. These drugs also exert an antianxiety effect, especially anxiety associated with phobia. The effects of the drugs vary greatly from patient to patient, and their specific actions leading to clinical benefits are poorly understood. Among the most common adverse effects are drowsiness, dry mouth, orthostatic hypotension, and constipation. Overdosage may cause tremor, euphoria, or manic behavior. MAO inhibitors interact with many drugs and with foods containing large amounts of the amino acid tyramine. Ingestion of these foods by a person taking an MAO inhibitor is likely to cause a severe hypertensive episode associated with headache, palpitations, and nausea. Among these foods are cheeses, red wine, smoked or pickled herring, beer, and yogurt. Among the drugs that interact with MAO inhibitors are dopamine, meperidine, and the indirect acting sympathomimetics, one of which, pseudoephedrine, is an ingredient in many common cold remedies. MAO inhibitors are also sometimes used in the treatment of migraine headache and hypertension. See also amine pump.
