Problem: Which statement about the mechanism of action of carbidopa is accurate? Carbidopa has no therapeutic effect on its own. Carbidopa works by crossing the blood-brain barrier. Carbidopa aids in the breakdown of levodopa in the peripheral tissues. Because of periphery loss of the medication, only 2% of carbidopa taken is available to the brain. Carbidopa-levodopa should not be taken with food. Carbidopa-levodopa should not be stopped abruptly. High-protein foods should be consumed with every meal. A decrease in the symptoms of Parkinson's disease occurs within a week of starting medication