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Dr. Bob is Robert Hsiung, MD,
bob@dr-bob.orgShown: posts 1 to 6 of 6. This is the beginning of the thread.
Posted by blueberry1 on January 13, 2007, at 3:18:59
I understand Deprenyl at low-medium doses is a MAOI-B inhibitor, not affecting serotonin or MAOI-A. But what about Ensam patch, say at 9mg or less. Does Ensam work as a MAOI-B and MAOI-A, or just MAOI-B?
Posted by SLS on January 13, 2007, at 5:04:59
In reply to ENSAM Question, posted by blueberry1 on January 13, 2007, at 3:18:59
> I understand Deprenyl at low-medium doses is a MAOI-B inhibitor, not affecting serotonin or MAOI-A. But what about Ensam patch, say at 9mg or less. Does Ensam work as a MAOI-B and MAOI-A, or just MAOI-B?
I believe you begin to see MAO-A inhibition at that dosage. I'll check the monograph and see if it says anything about it.
- Scott
Posted by SLS on January 13, 2007, at 5:10:57
In reply to Re: ENSAM Question, posted by SLS on January 13, 2007, at 5:04:59
> > I understand Deprenyl at low-medium doses is a MAOI-B inhibitor, not affecting serotonin or MAOI-A. But what about Ensam patch, say at 9mg or less. Does Ensam work as a MAOI-B and MAOI-A, or just MAOI-B?
>
> I believe you begin to see MAO-A inhibition at that dosage. I'll check the monograph and see if it says anything about it.Apparantly, MAO-A inhibition occurs at all dosages:
"CLINICAL PHARMACOLOGY
Pharmacodynamics
Selegiline (the drug substance of EMSAM) is an irreversible inhibitor of monoamine oxidase (MAO), an intracellular enzyme associated with the outer membrane of mitochondria. MAO exists as two isoenzymes, referred to as MAO-A and MAO-B. Selegiline has a greater affinity for MAO-B, compared to MAO-A. However, at antidepressant doses, selegiline inhibits both isoenzymes (see below). The mechanism of action of EMSAM as an antidepressant is not fully understood, but is presumed to be linked to potentiation of monoamine neurotransmitter activity in the central nervous system (CNS) resulting from its inhibition of MAO activity. In an in vivo animal model used to test for antidepressant activity (Forced Swim Test), selegiline administered by transdermal patch exhibited antidepressant properties only at doses that inhibited both MAO-A and MAO-B activity in the brain. In the CNS, MAO-A and MAO-B play important roles in the catabolism of neurotransmitter amines such as norepinephrine, dopamine, and serotonin, as well as neuromodulators such as phenylethylamine. Other molecular sites of action have also been explored and in this regard, a direct pharmacological interaction may also occur between selegiline and brain neuronal a2B receptors. In in vitro receptor binding assays, selegiline has demonstrated affinity for the human recombinant adrenergic a2B receptor (Ki = 284 µM). No affinity [Ki >10 µM] was noted at dopamine receptors, adrenergic ß3, glutamate, muscarinic M1-M5, nicotinic, or rolipram receptor/sites."
- Scott
Posted by halcyondaze on January 14, 2007, at 10:39:16
In reply to Re: ENSAM Question, posted by SLS on January 13, 2007, at 5:10:57
It is my understanding that it is dose-dependent. The higher the dose, the higher the MAO-A inhibition, which is why they saw a steady increase in the tyramine pressor response as dependent upon dosage.
[However, I was on 12 mg/day and I did not follow the diet for one second because, having read the research, felt it was uneccessary. And I am still alive, no hypertensive crises to report.]
Posted by SLS on January 14, 2007, at 11:48:44
In reply to Re: ENSAM Question, posted by halcyondaze on January 14, 2007, at 10:39:16
> It is my understanding that it is dose-dependent. The higher the dose, the higher the MAO-A inhibition, which is why they saw a steady increase in the tyramine pressor response as dependent upon dosage.
"selegiline administered by transdermal patch exhibited antidepressant properties only at doses that inhibited both MAO-A and MAO-B activity in the brain."
Perhaps the pressor response is dependent upon inhibition of gut MAO and not brain MAO?
- Scott
Posted by psychobot5000 on January 14, 2007, at 15:55:36
In reply to Re: ENSAM Question, posted by SLS on January 14, 2007, at 11:48:44
> Perhaps the pressor response is dependent upon inhibition of gut MAO and not brain MAO?
>
> - ScottFrom what I've been told, that is quite correct. If I remember right, a 6mg EMSAM, worn all day, will produce MAO-a inhibition of 70% or more, and above 90% of MAO-b. Yet, there is enough MAO-A left in the gut to prevent a pressor crisis. It's important to remember that blood levels of of selegiline from the patch are much higher than with tablets, so you get dual inhibition at all doses.
This is the end of the thread.
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