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Tyramine is a sympathomimetic amine normally metabolized by gut MAO-A. When tyramine rich foods such as red wines, pickled herring, or aged cheeses are ingested by someone taking an irreversible MAO-A inhibitor (clorgyline) or nonselective MAO inhibitor (e.g., phenelzine, tranylcypromine), the tyramine is absorbed rather than metabolized, causing norepinephrine release and potentially hypertensive crisis (26). This is known as the "cheese effect." Levodopa is contraindicated with MAO-A or non-selective MAO inhibitors, as it may cause a similar hypertensive crisis.

The MAO-B selective inhibitor selegiline (deprenyl, Eldepryl®) at oral doses up to 10mg/day is safe to be taken with levodopa and requires no dietary restrictions. Transient blood pressure changes have been reported with selegiline doses of 20 mg/day; therefore, doses above 10 mg/day are usually not recommended, as the selectivity may be lost. The second generation MAO-B selective inhibitor rasagiline (Azilect®) was approved in the European Union in 2005 and by the Food and Drug Administration (FDA) in the United States in May 2006. The risk of a tyramine reaction with rasagiline also appears to be very low at recommended dosages. In clinical trials, there were no tyramine reactions observed at the recommended doses, even when there were no dietary restrictions. However, because the dose at which rasagiline loses MAO-B selectivity is not known, it is currently recommended that patients on rasagiline avoid tyramine-rich foods and beverages.

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