MAO-INHIBITOR
MAO-Inhibitors
(Monoamine oxidase inhibitors) MAO-inhibitors work by blocking
an enzyme called monoamine oxidase. Some of the messenger
molecules (neurotransmitters)
of the brain, such as serotonin and norepinephrine, are
monoamines, and if you turn off this enzyme, the result
is more of these molecules accumulate. The result is therefore
essentially the same effect as using an SSRI.
More neurotransmitters build up between neurons and as a
result, the neurons increase in activity. The two most common
MAO-Inhibitors used today are Parnate (tranylcypromine sulfate)
and Nardil (phenelzine sulfate). The chemical structure
of Nardil is shown.
MAO
inhibitors work more rapidly than the tricyclics.
The problem with MAO-Inhibitors is due to the inadvertent
effect on another chemical called tyramine. Monoamine oxidase
enzyme usually also breaks down tyramine. If an MAO-inhibitor
is used, tyramine is not broken down as it usually is, and
levels of this chemical build up. Tyramine causes elevation
of blood pressure, so an increase in this chemical leads
to an increase in blood pressure which could lead to stroke,
heart attack, and other nasty side effects. Because of this,
people using MAO-inhibitors must avoid foods that are high
in tyramine, such as alcohol, legumes (e.g., fava and soy
beans), cheese, fish, ginseng, meat, sauerkraut, shrimp
paste, soups, and yeast extracts (baking yeast is OK in
small quantities).
The
long list of side effects of MAO-inhibitors may related
and unrelated to high blood pressure include dizziness,
fainting, headache, tremors, muscle twitching, confusion,
memory impairment, anxiety, agitation, insomnia, weakness,
drowsiness, chills, blurred vision, and heart palpitations.
If one stops an MAO-Inhibitor, the dose should be very slowly
tapered downward under the care of a physician.
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here for more information about specific drugs and side
effects.
