Monoamine oxidase inhibitors, or MAOI's, are drugs that block an enzyme in your body called monoamine oxidase. This enzyme breaks down chemicals in the brain called neurotransmitters, thereby inactivating them. Serotonin, norepinephrine, and epinephrine are all neurotransmitters broken down by monoamine oxidase. The monoamine oxidase inhibitors are primarily used to treat depression but may also be used in the treatment of Parkinson's disease. Although these agents are effective as antidepressants, their use is limited by many dietary restrictions.
Background
Monoamine oxidase not only breaks down monoamines, it also breaks down the amino acid tyramine. This substance occurs naturally in many kinds of foods. It is also found when bacteria breaks down proteins in old, spoiled, and fermented food. Monoamine oxidase inhibitors block the breakdown of tyramine, resulting in increased concentrations in your system. Some examples of MAOI's are phenelzine, generic for Nardil, tranylcypromine, generic for Parnate, selegiline, generic for Eldepryl, and Emsam, a patch containing selegiline.
Significance
If you eat foods containing high amounts of tyramine while on a monoamine oxidase inhibitor, you may experience a hypertensive crisis. This condition, considered a medical emergency, is when your blood pressure reaches dangerously high levels. Excessive amounts of tyramine raise your blood pressure. Extremely high blood pressure may cause a stroke, which in some cases may be fatal.
Foods Containing Tyramine
Many foods contain tyramine. Meats, fish, and poultry that have been cured or smoked, aged or fermented, pickled herring, sausage, pepperoni, salami, and bologna all contain significant amounts of tyramine. Sauerkraut, soy sauce, miso, fermented tofu, and fava bean pods also contain tyramine. All cheeses, and particularly aged cheeses -- except cream cheese and cottage cheese -- yogurt and yeast extract contain tyramine. Avoid these foods while taking an MAOI. If you stop taking an MAOI, wait two weeks before eating tyramine-containing foods.
Beverages Containing Tyramine
While taking an MAOI, you should avoid alcoholic beverages like beer and wine. Tap beers and some non-alcoholic and reduced-alcohol beers also contain tyramine. You should also avoid excessive consumption of caffeine-containing drinks.
Prevention/Solution
To prevent the interaction between your MAOI's and tyramine-containing foods, don't eat old or spoiled foods. Buy and eat only fresh or frozen foods. If you are unsure about the freshness of a food, don't eat it. Also, be aware of signs of dangerously high blood pressure. If you experience symptoms such as headache, rapid heartbeat, dizziness, neck stiffness, sweating, nausea, vomiting, dilated pupils, and/or light sensitivity, seek emergency medical treatment.
References
- Drugs.com: Parnate Prescribing Information
- Drugs.com: Nardil
- "Drug Information Handbook"; Charles Lacy, Lora Armstrong, Morton Goldman, Leonard Lance; 2008
