MAOIs, or "Monoamine Oxidase Inhibitors," are used to treat certain types of mental depression. They work by blocking the action of a chemical known as monoamine oxidase in the nervous system. These medications are the first known antidepressants but are now only prescribed when the more common forms of antidepressants, such as SSRIs (Selective Serotonin Reuptake inhibitors), do not work. One MAOI is also effectively used in the treatment of Parkinson’s disease. The reason these drugs are used as a last resort is that they can be potentially harmful when taken with other drugs and even from certain foods.
MAO inhibitors work by interfering with the enzyme that is responsible for metabolizing the three neurotransmitter chemicals in the brain: serotonin, norepinephrine and dopamine. MAOI’s increase the concentration of these chemicals and in turn, cause changes within specific areas of the central nervous system. The changes created by the drugs allow for the chemicals to be present in the brain in higher levels (SSRI antidepressants only work on serotonin), and thus, alleviate several forms of atypical, or rarer, more severe forms of depression.
MAOI’s are very effective in the treatment of depression. These drugs, however, pose serious and even fatal side effects if taken with other drugs or even with certain foods. Everyone is familiar with information posted on many over the counter drugs that most have in their home. The words “do not take with MAO drugs” or “do not take for at least two weeks after discontinuing an MAOI” are common under drug interaction. The reason many drugs interact with MAOIs is that the chemical norepinephrine, a powerful blood vessel constrictor that many over the counter medications increase, is also increased by MAOIs. With both medications increasing norepinephrine levels, the combination could pose potentially fatally high levels within the body.
Unfortunately, severe side effects from taking other medications with MAOIs are not the only potential danger. There are also certain foods that must also be avoided. Monoamine Oxidase is also found in the intestinal tract and is crucial in the breakdown of a substance named “tyramine.” MAOIs, while inhibiting the neurotransmitters, also alter the breaking down of tyramine and therefore, cause higher levels of the substance within the body. Ergo, foods that contain tyramine can result in such high levels that the individual may experience hypertension that can be potentially fatal.
If your physician feels that MAOIs are an appropriate treatment, there are only four FDA approved medications available. One of these medications, selegeline (brand name Emsam) is not used for depression but instead for the treatment of Parkinson’s disease. The drug works as an antioxidant and an immunostimulant which protects nerve tissue from degeneration and has positive effects on cognition. The drug is usually prescribed in addition to the most commonly used Parkinson’s medication, L-Dopa and has proven to be effective.
The other three MAOIs are: Isocarboxazid (brand name Marplan), phenelzine (brand name Nardil) and Tranylcypromine (brand name Parnate). These drugs are equally prescribed and one is not known as having more efficacy than another. It is important to remember that these drugs are not widely prescribed as their side effect potential is so dangerous, thus not nearly as many clinical tests are conducted. Monitoring a patient’s diet as well as other medications over the counter or prescribed from another doctor are extremely difficult to monitor, and physicians typically do not want the liability of prescribing a drug which can have potentially fatal results.
Clearly, MAOIs are used only when all other medications have been ruled out as effective treatments for depression. If your physician feels you may benefit from MAOIs it is imperative that you research possible drug interactions as well as foods to avoid any dangerous side effects. Your physician will provide you with a comprehensive list of all possible drug interactions as well as foods that should be avoided while taking MAOIs. If not, it is the patient's responsibility to ask for it. It is also important to read all over the counter medications and discuss them with your physician before taking them. If taken properly, MAOIs can provide many patients with relief from a depression that has plagued them and evaded medical treatment in the past.