Which statement accurately describes the mechanism of carbidopa-levodopa?

Which statement accurately describes the mechanism of carbidopa-levodopa?

• A. Carbidopa directly inhibits dopamine receptors.
• B. Levodopa is converted to dopamine in the brain, and carbidopa prevents breakdown of levodopa in the periphery.
• C. Carbidopa increases serotonin in the brain.
• D. Levodopa cures Parkinson.

Answer: (B)

This question focuses on how the combination works to treat Parkinson’s symptoms. Levodopa acts as a dopamine precursor that can cross into the brain, where it is converted to dopamine to replace the deficient neurotransmitter signaling. Carbidopa, a peripheral decarboxylase inhibitor, blocks the conversion of levodopa to dopamine outside the brain. Because it mostly stays outside the CNS, it prevents premature breakdown of levodopa in the periphery, which both reduces peripheral side effects (like nausea and cardiovascular effects) and increases the amount of levodopa that reaches the brain to be converted into dopamine. This combination manages symptoms, but it does not cure the disease. It does not increase serotonin or directly affect dopamine receptors.

This question focuses on how the combination works to treat Parkinson’s symptoms. Levodopa acts as a dopamine precursor that can cross into the brain, where it is converted to dopamine to replace the deficient neurotransmitter signaling. Carbidopa, a peripheral decarboxylase inhibitor, blocks the conversion of levodopa to dopamine outside the brain. Because it mostly stays outside the CNS, it prevents premature breakdown of levodopa in the periphery, which both reduces peripheral side effects (like nausea and cardiovascular effects) and increases the amount of levodopa that reaches the brain to be converted into dopamine. This combination manages symptoms, but it does not cure the disease. It does not increase serotonin or directly affect dopamine receptors.