Jack understands that levodopa is the mainstay of treatment for Parkinson disease and asks the NP why he is on
the combination drug carbidopa/levodopa.
What would be the best explanation the NP could give Jack on why the dopaminergic agent carbidopa/levodopa is
more effective than the dopaminergic agent levodopa alone in minimizing the symptoms of Parkinson disease?
When used together, they inhibit the enzyme dopa decarboxylase in the periphery,
diminishing the metabolism of levodopa in the GI tract and in peripheral tissues, which
leads to higher levels of the drug crossing the blood-brain barrier
When used together, they prolong the effect of levodopa by blocking an enzyme, COMT,
which eliminates dopamine and increases the plasma concentrations and duration of
action of levodopa
When used together, they act to increase the level of ACh in the CNS by inhibiting its
breakdown and slowing neural destruction
When used together, they block certain neurotransmitter receptor sites, which potentiates
the effects of the inhibitory transmitter gamma (y)-aminobutyric acid (GABA)