Monoamine oxidase inhibitors (MAOIs)

Monoamine oxidase inhibitors (MAOIs) were the first type of antidepressant in use, dating back to the 1950s. Researchers believe MAOIs relieve depression by preventing the enzyme monoamine oxidase from metabolizing the neurotransmitters norepinephrine (nor-ep-ih-NEF-rin), serotonin (ser-oh-TOE-nin) and dopamine (DOE-puh-mene) in the brain. As a result, these levels remain high in the brain, boosting mood.

Here are the MAOIs that have been specifically approved by the Food and Drug Administration to treat depression, with their generic names followed by available brand names in parentheses:

• Phenelzine (Nardil)
• Tranylcypromine (Parnate)
• Isocarboxazid (Marplan)
• Selegiline (Emsam)

Side effects and safety concerns

Because they can cause serious side effects, MAOIs are usually reserved for people who don't respond to other antidepressant medications first.

Side effects of MAOIs include:

• Drowsiness
• Constipation
• Nausea
• Diarrhea
• Stomach upset
• Fatigue
• Dry mouth
• Dizziness
• Low blood pressure
• Lightheadedness, especially when getting up from a lying or sitting position
• Decreased urine output
• Decreased sexual function
• Sleep disturbances
• Muscle twitching
• Weight gain
• Blurred vision
• Headache
• Increased appetite
• Restlessness
• Shakiness
• Trembling
• Weakness
• Increased sweating

MAOIs can cause dangerous interactions with certain foods, beverages and other medications. If you take these medications, you'll face dietary restrictions that require you to limit consumption of foods that contain a high level of tyramine, such as many cheeses, pickled foods, chocolates, certain meats, beer, wine and alcohol-free or reduced-alcohol beer and wine. The interaction of tyramine with MAOIs can cause a dangerously high increase in blood pressure, which can lead to a stroke. Your doctor can give you a complete list of dietary restrictions.

The exception to this is Emsam. Emsam is the first skin (transdermal) patch for depression, approved by the Food and Drug Administration in February 2006. At its lowest dose of 6 milligrams a day, you don't need to follow those dietary restrictions. At higher doses of Emsam, you do, though.

Don't take MAOIs with selective serotonin reuptake inhibitors (SSRIs) because of the risk of the potentially life-threatening condition serotonin syndrome. Signs and symptoms of serotonin syndrome include confusion, hallucinations, extreme agitation, fluctuations in blood pressure and heart rhythm, increased sweating, muscle rigidity, fever, seizures and even coma. Serotonin syndrome requires immediate medical treatment.

In some cases, antidepressants may be associated with worsening symptoms of depression or suicidal thoughts or behavior, particularly early in treatment or when you change your dosage. Be sure to talk to your doctor about any changes in your symptoms. You may need more careful monitoring at the beginning of treatment or upon a change in treatment, or you may need to stop the medication if your symptoms worsen.