Monoamine oxidase inhibitors (MAOIs) are a class of antidepressant drugs prescribed for the treatment of depression. Due to potentially serious dietary and drug interactions they 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, sometimes with a marked success. They are particularly effective in treating atypical depression, and have shown efficiacy in quitting smoking.

In the past they were prescribed for those resistant to tricyclic antidepressant therapy, but newer MAOIs are now used as an alternative to tricyclics. They are also used for treating agoraphobia. MAOIs, in their original form presented an unusual problem for the prescribing physician. If a physician was prescribing MAOIs for depression, he/she had to take into consideration the fact that he/she was offering the patient a ready, though unpleasant, route to suicide. Currently, the availability of deprenyl and moclobemide provides a safer alternative, although not always as effective as the old types. Transdermal delivery may prove a safe alternative.

MAOIs act by inhibiting the activity of monoamine oxidase preventing the breakdown of monoamine neurotransmitters and so prolonging their effect. Some MAOIs can potentiate the action of a number of other drugs; when ingested orally, they also inhibit the metabolism of the amine tyramine, so that tyramine-containing foods can trigger hypertensive attacks, occasionally with fatal results. Examples of tyramine-containing foods include such common foods as liver, broad beans, Chianti and other aged wines, aged cheeses, meat extracts (e.g. Bovril) and yeast extracts (e.g. Marmite, Vegemite). However, some types of MAOIs do not have these effects. Conveniently, Syrian Rue (one of the most common and cheapest plant varieties) is one of these "reversible" MAOIs.

Combined use of non-selective MAO inhibitors or MAO-A inhibitors and serotonergic drugs is likely to lead to serotonin syndrome.

MAOIs are also used to enhance the effect and duration of N,N-dimethyltryptamine based hallucinogens, commonly used by shamans in South American indigenous tribes to extend the duration of DMT based rituals. Additionally, many claim that plant MAOIs (most often Syrian rue) can be used to potentiate the effects of almost any recreational drug, although it completely neutralizes the effect of e.g. LSD.

Monoamine oxidase inhibitors include:

• Isocarboxazid (Marplan)
• Moclobemide (Manerix, Moclodura®)
• Phenelzine (Nardil)
• Tranylcypromine (Parnate)
• Deprenyl (Selegiline, Eldepryl)
• Ayahuasca generally in the form of Banisteriopsis caapi or Syrian rue (harmine and harmaline).

External links

• http://www.erowid.org/chemicals/maois/maois.shtml