Monoamine Oxidase Inhibitors

  1. What is a monoamine oxidase? What is its function in the body?

  2. How does the MAOI work?

  3. What are the known MAOI substances?

  4. I would like a comprehensive list of foods that are hazardous to eat in the presence of MAOI. Fermented, pickled, and cured foods in general? Chocolate? Coffee??? What are the health hazards in this combination?

MAO is an enzyme that break downs many neurotransmitters. Neurotransmitters are chemicals that communicate the signal between nerve cells. Examples of neurotransmitters that MAO breaks down are adrenalin, noradrenalin, dopamine, and I think also serotonin. These are all, in some sense, “activating” neurotransmitters.

MAOI’s inhibit MAO’s and thus lead to higher concentrations of the above neurotransmitters.

Some foods contain tyramine, a precursor of these same neurotransmitters. So, if you eat those foods and also take an MAOI, you can get extremely high levels of the neurotransmitters. This can lead to things like very high blood pressure, fever, seizures, etc.

Foods containing tyramine include aged cheese and red wine. I’m sure you can find more on the Web about this aspect.

Certain drugs like Demerol also potentiate the effect of MAOI’s and must not be used concurrently with them. Once more, I’m sure that more information on this is available somewhere online.

MAOI’s are used to treat depression (where there may be a lack of the above neurotransmitters) and also Parkinson’s Disease (where the breakdown products of certain neurotransmitters can be toxic to certain parts of the brain, and also where there is a deficiency of dopamine).

Hope this is of some help.

Here’s a link to some of the foods you need to avoid:

You don’t see too many people taking these drugs anymore.

Everyone makes a big deal of tyramine crisis (reaction between old cheese and MAOIs), but it has never been particularly common AFAIK. The newer class of MAOIs cause this crisis far less often than the old ones, and have far fewer dietary restrictions.

my pharm text book says
no cheese, pickled herring, red wine (esp chianti) or broad beans, also no vegemite, marmite, bovril or similar meat or yeast extracts.

no cough medicines containing pseudoephidrine,
no L-dopa (except with selegiline for PD),
no lidocaine, no epinephrine, no norepinephrine, no isoprenaline,
no pethidine
no Tri-cyclic anti depressants
no sulphonyl urea and other oral hypoglycaemics
no methlydopa
no reserpine

and they’re contra-indicated with liver disease.

fun drugs.

oh, BTW MAO has alpha and beta sub classes.
beta is selectively found in the brain, and selegiline acts only on it, that’s why selegiline is used for PD.
most other MOAI are non-selective and inhibit both alpha and beta sub-groups.

if you’re REALLY interested,
it has been shown that by knocking out the gene which codes for MAOa in rats, so they don’t produce MAOa, they become hyper-agressive.
my biochem lecturerer is one of the people who discovered MOAIs…he calls the effect on the rats the “Manchester United effect” because the hyper aggressive rats remind him of MU fans.