What Is a Mao Inhibitor?

As the first class of drugs developed for the treatment of depression, Monoamine Oxidase Inhibitors (MAOIs) feature the longest history among all anti-depressant medications. Introduced during the 1950's, MAOIs allow certain neurotransmitter levels to remain elevated in the brain thereby boosting the moods of depression patients who use them.

Use

MAOIs are typically recognized for the powerful medicinal influence they have in the treatment of depression. Less commonly known is that MAOIs have a particular effectiveness when prescribed in the treatment of atypical depression (a major-depression subtype characterized by the ability to experience a lightening or uplifting of mood in response to a positive situation or event). Similar efficacy has also been demonstrated by MAOIs when used in efforts to cease smoking.

Function

MAO-Inhibitors interfere with the normal activities of monoamine oxidase, an enzyme responsible for metabolizing, or breaking down, monoamine neurotransmitters. These transmitters are in turn responsible for the breakdown of specific neurons used to activate vital functions of the central nervous system, including serotonin, dopamine, norepinephrine, and epinephrine. Psychiatric research has shown these neurons to be associated with depressive episodes. So by inhibiting the ability of monoamine oxidase to metabolize the monoamine neurotransmitters, MAO-Inhibitors ultimately prevent the metabolizing of these CNS neurons leaving them in abundance. In higher concentrations, these CNS neurons change the system itself; and it is the changing of the nervous system (as induced by the MAOI) that is credited with the observed decrease in depression symptoms.

Types

There are three types of irreversible MAO-Inhibitor drugs prescribed for the treatment of depression with the approval of the Food and Drug Administration.

Phenelzine (Nardil, Nardelzine) is typically prescribed as an antidepressant medication that can be used as an anti-anxiety and anti-panic agent. It is considered to be highly effective in treating clinical depression but is reluctantly prescribed given the potential for harmful side effects and dietary interactions.

The same applies to Tranylcypromine (Parnate, Jatrosom), another MAOI that acts as both an antidepressant and anti-anxiety medication in the treatment of anxiety and mood disorders.

Likewise, Isocarboxazid (Marplan) is an MAOI used to treat depression, anxiety and panic disorders including those that include agoraphobia as a comorbid condition.

Depressive Conditions

There is only one type of selective-irreversible MAO-Inhibitor drug available to those who suffer from depressive conditions: Selegiline (l-deprenyl, Eldepryl, Zelapar). Although this drug can be prescribed to treat depression, it is primarily used to treat Parkinson's disease and senile dementia. Approved by the FDA in 1996, it is the only MAOI that features transdermal, rather than oral, administration in the form of a patch.

Warning

MAO-inhibitors carry the potential to interact negatively, even lethally, with some dietary substances. This is particularly the case with foods containing tyramine or medications that contain sympathomimetic agents, such as epinephrine-like medications such as amphetamine and albuterol. The oral administration of most MAOIs means that the medication enters the gastrointestinal system, which exacerbates this reaction; however, the newer transdermal administration of the patch MAOI has shown to decrease the danger of MAOI and dietary interactions.