Potentiation of the cardiovascular and other effects of dietary tyramine by monoamine oxidase (MAO) inhibitors (cheese effect) has been a major limitation to clinical use of these drugs. The discovery that MAO exists in two distinct isoforms, MAO-A and MAO-B, together with the development of selective inhibitors of each isoform, enabled the understanding that selective inhibition of MAO-A, or inhibition of both isoforms, will cause cheese effect, but selective inhibition of MAO-B can be elicited without dangerous pressor reaction. This development has permitted the introduction of selective MAO-B inhibitors to clinical medicine for treatment of Parkinson's disease. This review describes the basic mechanisms involved in cheese effect, as well as providing information on tyramine levels in a variety of foodstuff, and surveys clinical information from tyramine pressor testing with the selective MAO-B inhibitors, selegiline and rasagiline.
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