Monoamine oxidase inhibitors – MAOIs
Because of potentially lethal dietary and drug interactions, monoamine oxidase inhibitors have been reserved as a last line of treatment, used only when other classes of antidepressant drugs have failed.
MAOIs act by inhibiting the activity of monoamine oxidase, thus preventing the breakdown of monoamine neurotransmitters and thereby increasing their availability.
There are two isoforms of monoamine oxidase, MAO-A and MAO-B.
MAO-A preferentially deaminates (removes/breaks down) serotonin, melatonin, epinephrine, and norepinephrine.
MAO-B preferentially deaminates (removes/breaks down) phenylethylamine and trace amines.
Dopamine is equally deaminated (removed/broken down) by both types.
MAOIs inhibit the catabolism (break down) of dietary amines.
If foods containing Tryptophan are consumed, Hyperserotonemia (Serotonin Syndrome) may result.
When foods containing Tyramine are consumed, the individual may suffer from hypertensive crisis.
It is assumed that tyramine displaces Norepinephrine from the storage vesicles. This may trigger a cascade in which excessive amounts of Norepinephrine can lead to a hypertensive crisis. Another theory suggests that proliferation (increase) and accumulation of catecholamines causes hypertensive crisis.
Tyramine Rich Foods:
- produced by the decarboxylation of tyrosine during fermentation or decay
- meats that are potentially spoiled or pickled, aged, smoked, fermented, or marinated – some fish, poultry, and beef, most pork (except cured ham)
- alcoholic beverages
- fermented foods
- most cheeses (except ricotta, cottage, cream and neufchatel cheeses
- sour cream
- shrimp paste
- soy sauce
- soybean condiments
- teriyaki sauce
- miso soup
- broad (fava) beans
- green bean pods
- Italian flat (Romano) beans
- snow peas
- red plums
- Brazil nuts
- processed meat
- array of cacti
The MAOIs are infamous for their numerous drug interactions.