Posted by Larry Hoover on October 11, 2007, at 20:41:18
In reply to What is 'Irreversible' MAO Inhibition?, posted by War-Face on October 9, 2007, at 10:36:51
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> Does this mean that the effects on MAO are permanent and that after taking an MAOI, you have to follow the diet for the rest of your life? I am unsure about what this means.
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> I'm interested in Emsam particularly, which I know seems pretty irregular as far as MAOIs for the delivery mechanism.I can see why you're a little confused.
Every day, every hour, your body churns out a little bit of the enzyme monoamine oxidase. At about the same rate as it is synthesized, some of it is destroyed/recycled back to the constituent amino acids. So, at any point in time, the total amount of this enzyme is relatively constant, as the rate of formation is roughly equal to rate of destruction. That's called a dynamic equilibrium. The whole cycle is thought to take as little as two weeks, but might be a little longer.
There are some drugs that interact with the MAO enzyme, inhibiting its "designed" activity, which is to break down monoamine neurotransmitters, and similar. Inhibitors fall into two broad classes, the reversible and the irreversible. A reversible inhibitor binds to the enzyme in such a way as to block its action, but it does not affect the molecular structure. If the inhibitor breaks contact with the MAO, then its inhibition is reversed. The fully functional MAO enzyme can go back to what it was intended to do. It's like somebody parking their car in your spot. You can't park there until it moves on. Moclobemide is one such inhibitor.
In contrast, some inhibitors change the function of the MAO by chemical disruption. They either permanently bond to the enzyme active site, or damage it and leave. In either case, the enzyme cannot function. The inhibition is irreversible. Like frying an egg.
Recall, though, that I said your body churns out a little bit of MAO every hour. If the newly formed MAO does not encounter an inhibitor, it can immediately start to function. Of course, the total MAO effect also relies on the accumulated enzyme concentration over a few weeks of normal production. So, if you stop taking an irreversible inhibitor, the concentration of functional MAO will gradually build. After a week or so, the total MAO activity will be perhaps a half of normal. By two weeks or so, it will have gotten back pretty much to normal.
Lar
poster:Larry Hoover
thread:788064
URL: http://www.dr-bob.org/babble/20071009/msgs/788595.html