A Patient Has Been Given a Prescription for Levodopa-Carbidopa (Sinemet)

A patient has been given a prescription for levodopa-carbidopa (Sinemet) for a new diagnosis of Parkinson's disease. The patient asks the nurse, "Why are there two drugs in this pill?" The nurse's best response reflects which fact?

A) Carbidopa allows for larger doses of levodopa to be given.
B) Carbidopa prevents the breakdown of levodopa in the periphery.
C) There are concerns about drug-food interactions with levodopa therapy that do not exist with the combination therapy.
D) Carbidopa is the biologic precursor of dopamine and can penetrate into the central nervous system.