Monoamine Oxidase Inhibitors (MAOIs)

What are Monoamine Oxidase Inhibitors (MAOIs)?

Monoamine oxidase inhibitors (MAOIs) are a class of antidepressants prescribed for the treatment of depression. MAOIs can have potentially serious dietary and drug interactions. As a result, MAOIs are used less frequently than other classes of antidepressant drugs (for example tricyclic antidepressants and selective serotonin reuptake inhibitors). However, in some cases where patients are unresponsive to other treatments they are tried, often with a marked success. They are particularly effective in treating atypical depression, and have shown efficacy in helping smokers to quit smoking.

In the past, monoamine oxidase inhibitors were prescribed for those resistant to tricyclic antidepressant therapy, but newer MAOIs are now sometimes used as first-line therapy. MAOIs are also used for treating agoraphobia.

How Monoamine Oxidase Inhibitors (MAOIs) Treat Depression

MAOIs act by inhibiting the activity of monoamine oxidase. By preventing the breakdown of monoamine neurotransmitters, MAOIs increasing the available stores. There are two isoforms of monoamines: MAO-A and MAO-B. MAO-A preferentially deaminates serotonin, noradrenaline (norepinphrine) and melatonin, while MAO-B preferentially deaminates phenylethylamine and trace amines. Dopamine is equally deaminated by both MAO-A and MAO-B.

Imporatant Information About Monoamine Oxidase Inhibitors (MAOIs)

MAOIs can potentiate the action of a number of other drugs. Drugs that may have an increased effect when taking MAOIS include opiates, ephedrine, and adrenaline (epinephrine).

When MAOIs ingested orally, they also inhibit the catabolism of dietary amines. This may cause:

hypertensive crises when foods containing tyramine are consumed,
hyperserotonemia if foods containing tryptophan are consumed, or
hyperpyrexia if levodopa-containing foods are consumed.

Examples of foods with high levels of tyramine include liver, Chianti and other aged wines, aged cheeses, meat extracts (e.g. Bovril) and yeast extracts (e.g. Marmite, Vegemite). Examples of trytophan-containing foods include bananas and nuts. Examples of levodopa-containing foods include broad beans.

Hypertensive crises can sometimes result in stroke or cardiac arrythmia if not treated. This risk is not present with reversible monoamine inhibitors (RIMAs).

Examples of Monoamine Oxidase Inhibitors (MAOIs)

The following are some available brands of monoamine oxidase inhibitors (MAOIs):

Moclobemide (Aurorix, Manerix) - Moclobemide is a Reversible Monoamine Inhibitor (RIMA)

Tranylcypromine (Parnate)

Phenelzine (Nardil)

Deprenyl (Selegiline, Eldepryl)

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