Brian wrote:
>>> Brian Collins <[log in to unmask]> 02/03/98
08:53pm >>>
Hello friends, There seems to be some confusion about the
role of some of
the PD drugs . . . Currently, there is only one COMT
inhibitor : Tasmar (Tolcapone) . . . to inhibit the
formation of a chemical called COMT: COMT in its turn can
break down Dopamine . . . My neuro recently
told me that Tasmar actually does its thing in the body, NOT
in the brain!!<<<
-- Brian Collins <[log in to unmask]>
Hello Brian:
When levodopa (without carbidopa or benserazide
["Madopar"] ) is given to a patient with PD, it is metabolized
into dopamine, by enzymes OUTSIDE the brain. This results
is nausea and vomiting.
Sinemet (sin = without & emet = vomit) combines
carbidopa with levodopa to inhibit the metabolism of levodopa
in the liver, making more available to cross into the brain. *I
don't know what "Madopar" means.
With Sinemet, any remaining metabolism of levodopa in
the body is the job of the enzyme catechol-o- methyl-
transferese (COMT). Researchers believe that the further
inhibition of the metabolism of levodopa in the body, by
interfering with the COMT mechanism, will result in more
movement of the levodopa (Sinemet) into the brain. Also
there is evidence that levodopa in the blood stream is
prolonged (half-life) which increases blood concentration of
levodopa. It is levodopa in the blood, not necessarily in the
brain that doctors are looking to prolong.
There are two COMT inhibitors under trial:
Tolcapone-which acts in the brain and the liver and,
Entacapone-which only acts in the liver. It is believed that
patients taking Tolcapone can reduce their Sinemet dose
and still enjoy less daily motor fluctuations.
Stephan 53/7
