Monoamine oxidase inhibitors, also know as MAO inhibitors or MAOIs, became the first antidepressants on the market in the 1950s. The medications remain a treatment option but doctors will likely try them as a last resort due to their numerous potential side effects.

Function

MAO inhibitors block the enzyme monoamine oxidase from metabolizing the mood-altering neurotransmitters serotonin, norepinephrine and dopamine. The levels of these neurotransmitters therefore remain high, improving mood.

MAO Inhibitors

The MAO inhibitor medications phenelzine, tranylcypromine, isocarboxazid and selegiline sell in the United States under the respective brand names of Nardil, Parnate, Marplan and Emsam.

Common Side Effects

Common mild side effects of MAO inhibitors include drowsiness, constipation, nausea, decreased sexual function, weight gain and sleep disturbances. Contact your doctor if the symptoms persist or worsen.

Interactions

Inform your doctor of any medications or supplements you take before beginning treatment with MAO inhibitors. These medications tend to interact negatively with pain medications such as Ultram, decongestants and St. John's wort.

Serotonin Syndrome

MAO inhibitors should not be taken concurrently or within two weeks of antidepressants in the selective serotonin reuptake inhibitors (SSRIs) class. Concurrent dosing may cause dangerously high levels of serotonin to build up. Symptoms of the potentially fatal condition include hallucinations, fever, seizures and coma.

Source:

Mayo Clinic: MAOIs