Nature of MAOIs

Monoamine oxidase inhibitors are later category medications after tricyclics. They act on the same neurochemicals, serotonin and norepinephrine, but they act on another chemical called dopamine. These neurochemicals, called neurotransmitters, act as message carriers between nerve cells. They are found in the synaptic space between nerve ends. But these neurotransmitters are affected by an enzyme called monoamine oxidase. This enzyme metabolizes these neurotransmitters and destroys them, resulting in the reduced availability of these neurotransmitters in the brain. This may result in a person descending into depression, as low serotonin levels and depression are found to be co-existent in a person. A depressed person is found to possess lower levels of serotonin than a normal person.

Working of MAOIs

Basically, all these neurotransmitters - such as serotonin, norepinephrine, and dopamine - are monoamines. Another monoamine, monoamine oxidase, acts on these other neurotransmitters and cleans up their supply in the brain. Monoamine oxidase inhibitors, as the name suggests, inhibit or retard the cleaning up of these useful neurotransmitters from the system. These inhibitors block this clearing activity. As depressive disorders are associated with low serotonin supply in the brain, any activity that helps in maintaining the availability of serotonin and other neurotransmitters in the brain is bound to lift a person from depression. These monoamine oxidase inhibitors help in restoring the neurochemical balance in the central nervous system.

In addition to cleaning up these neurotransmitters, monoamine oxidase also affects another amine called tyramine, a building block of norepinephrine, a substance that is directly responsible for blood pressure levels. When the culprit of depression, the monoamine oxidase, is prevented from playing havoc with the balance of neurotransmitters in the system, it will, in the process, also let tyramine level to increase. The situation of uncontrolled increase in tyramine level in the system is a serious problem. While increases in serotonin, etc., neurotransmitters are welcome, the tyramine increase will be disastrous. Tyramine is capable of inducing an abrupt and phenomenal increase in blood pressure level which may become life-threatening activity sometimes. It may cause intracerebral hemorrhage.

When a person is excited and is in a state of euphoria, inevitably the body resources of neurotransmitters get depleted. Further, when MAOIs are in action, biogenic (substances produced in the body) amines can not be modified into catecholamines (catecholamines are hormones that are secreted by the adrenal glands when there is stress or faced with low blood sugar), causing a drop in the supply of these chemicals. This will lead to respiratory difficulties, cardiac dysfunction and death.

MAOIs, when ingested, are rapidly metabolized and excreted out of the system. But the effects of passive and inhibiting character of these chemicals remain for about two weeks even after the medication is discontinued.

MAOIs and Prohibited Foods

Many foods and food items contain tyramine which, combined with MAOI medication, will cause an increase in blood pressure, chest pains, palpitations, etc. When the tyramine level increases drastically, it will result in intracerebral hemorrhage, cardiac arrhythmia and cardiac failure. There are certain food items and beverages that should be avoided while under MAOI treatment.

Foods and food items to avoid:

• Seasoned cheeses
• Red wines, beers and ales, vermouth, sherry, nonalcoholic beer and wine
• Broad beans
• Sauerkraut
• Soya sauce and tofu
• Caviar
• Aged meats
• Italian green beans
• Snow pea pods
• Soy products, especially soy sauce and tofu
• Concentrated yeast extract, and all yeast products
• Acidophilus and products with acidophilus
• Overripe fruits and food items
• Banana skins

Certain Aspects of MAOIs

Indications: MAOIs are prescribed for depression, insomnia, panic disorders and anxiety. They are also useful in treating Parkinson’s disease. It is also used for the treatment of the neurodegenerative disease multiple system atrophy (MSA).

Efficacy: MAOIs are employed as a second-preference treatment in adults with major depressive disorder who do get any cure from other antidepressants. There is 50%-70% treatment efficiency with MAOIs for tricyclic (tricyclic antidepressants) resistant depression.

Tolerance: Some patient may become immune to the MAOI treatment. Efficacy may come down. To treat depression in people with such condition, it is advisable to make a switch to other antidepressants for treatment for a few weeks, then restart medication with MAOIs.

Toxicity: The toxic effects with overdose of MAOI are hyperthermia, skeletal muscle rigidity, tachycardia, metabolic and respiratory acidosis, electrolyte abnormalities, cardiac arrhythmias, renal failure, temperature, increased blood pressure, pulse and respirations, wakefulness, etc.