http://www.parkinsonswny.com/Parkinson-Handbook.pdf

2004 date but a lot of stuff in there i didn't know. some things out of date.


Because of the nausea many
patients experience when taking levodopa alone, it is usually taken in
combination with carbidopa (trade name: S i n e m e t). This nausea is caused by
the conversion of levodopa to dopamine in the intestine and blood before
levodopa reaches the brain, and by direct stimulation by levodopa of the
vomiting center in the brain. Carbidopa blocks the conversion of levodopa to
dopamine only in the intestine and blood (not in the brain) and thereby
markedly reduces the incidence of nausea and vomiting. It also ensures that
more levodopa goes into the brain and is not wasted by conversion to
dopamine in the blood or intestine. Patients taking the combination, therefore,
require less levodopa per dose than if they take levodopa alone. For these
reasons it is the most common form in which patients take levodopa.
Levodopa/carbidopa comes in two forms, s t a n d a r d and c o n t r o l l e d - r e l e a