A nursing student wants to know why a patient who has been taking levodopa for years will now receive levodopa/carbidopa. The nurse explains the reasons that levodopa as a single agent is no longer available. Which statement by the student indicates an understanding of the medications mechanism of action?

A. Carbidopa allows levodopa to be utilized in the periphery: Carbidopa does not promote peripheral utilization of levodopa. Instead, it prevents peripheral breakdown of levodopa, allowing more of the drug to reach the brain where it is needed. B. Carbidopa controls the side effects of levodopa in the body: Carbidopa inhibits the enzyme dopa-decarboxylase in the periphery, reducing peripheral conversion of levodopa to dopamine. This lowers side effects such as nausea, vomiting, and orthostatic hypotension, while also enhancing levodopa’s availability for the brain. C. Carbidopa helps carry levodopa across the blood brain barrier to be utilized: Carbidopa does not facilitate the transport of levodopa across the blood-brain barrier. Levodopa itself crosses the barrier, while carbidopa remains in the periphery to prevent premature metabolism. D. Carbidopa/levodopa inhibits the breakdown of dopamine in the brain: The combination does not directly inhibit dopamine breakdown in the brain. Instead, levodopa is converted into dopamine once inside the brain, and carbidopa reduces peripheral breakdown so more levodopa is available to enter the central nervous system.