Dawn you asked:
>>> "M.Dawn Legan" <[log in to unmask]> 02/11/98
03:12pm >>>
>>>does the carbidopa accumulate throughout the day,
eventually reaching 75mg? As a matter of fact, does the
levodopa accumulate? And perhaps even more importantly,
is there a minimum therapeutic level, especially of the
carbidopa?<<<
Greetings Dawn:
Carbidopa inhibits the conversion of levodopa outside the
brain, which allows much larger amounts of the levodopa
from each dose to be transported by the blood stream,
across the blood-brain barrier into the central nervous
system.
Carbidopa does this by limiting the action of a specific
enzyme - dopa decarboxylase - in the liver and other body
tissues. The "saturation" or optimum neutralization level of
carbidopa in the blood varies from 70 to 100mg daily
(depending upon a particular patient's life-style and
metabolism).
As a general rule, patients taking a dose of levodopa who
have lower than 70 mg carbidopa (available during absorption
of the levodopa into the blood) present in the peripheral
(non-cerebral) tissues will experience some nausea or
vomiting.
Both carbidopa and levodopa breakdown in the
gastro-intestinal tract. Each has a therapeutic half-life of
effectiveness of about 5 to 6 hours. Therefore, Drs. usually
recommend that doses be administered at three times per
day in quantities sufficient to maintain optimum blood plasma
levels for the patient during the awake hours.
The different combination doses of carbidopa/levodopa
available to the patient allow for adjusting ("micro manage")
both the carbidopa and levodopa intake to maintain
maximum levels of levodopa in the blood stream throughout
the day.
Good luck.
Stephan 53/7
