Monoamine oxidase inhibitors, or MAOIs, are an older class of antidepressants that work by inhibiting enzymes that break down monoamine neurotransmitters in the brain (serotonin, norepinephrine and dopamine), which may alleviate depression. Unfortunately, MAOIs interact with a large number of foods, especially fermented or aged foods like wine, tofu and soy sauce, many cheeses, pickles and sauerkraut, as well as with many over-the-counter medications. However, for some people with depression, particularly those with atypical or treatment-resistant depression, MAOIs may be the only drug that will work. They are also used to treat social anxiety and to help people quit smoking.
Nonselective and Irreversible MAOIs
The original MAOIs were prescribed more often in the 1950s to 1970s, although they continue to be in use today. Medically speaking, they were considered to be nonselective, which means that they inhibit all monoamine oxidase activity. They are also irreversible, which means that they permanently inhibit the enzymes that destroy monoamines, and it may take up to two weeks for the body to create more of these enzymes. The antidepressant effect of older MAOIs is very quick, and they may be used in a crisis situation. However, they are also rather harsh medicines with strong side effects, such as insomnia, headache, nausea and feeling jittery or wired. Some nonselective and irreversible MAOI drugs are sold under the brand names Nardil and Parnate.
Selective and Reversible MAOIs
Newer versions of MAOI drugs are more gentle, and they are often selective and reversible. Selective MAOIs are designed to affect only specific brain chemicals. MAO-A inhibitors boost norepinephrine, dopamine and serotonin, while MAO-B Inhibitors boost only dopamine. MAO-B inhibitors do not carry the same dietary restrictions as MAO-A inhibitors or nonselective MAOIs. Many of the newer MAOIs are also reversible, which means that monoamine oxidase enzymes are not permanently disabled, and the body goes through less shock and upheaval than with older MAOIs, although many people will still experience some side effects. Some selective and reversible MAOI drugs include Moclobemide and Rolipram.
MAOI Patch
In 2006 the FDA approved an MAOI skin patch for use in treating depression. The patch uses the drug selegiline and is marketed under the brand name Emsam. By absorbing MAOI drugs through the skin, they reach the bloodstream more quickly and effectively than they would if taken orally. Since the drugs in the MAOI skin patch bypass the intestine and stomach, dietary restrictions are often not necessary, especially at low doses. Side effects of the MAOI skin patch are generally much lower that those of oral MAOIs.
