Final answer:
The combo drug carbidopa-levodopa is used to provide the brain with levodopa, which is converted into dopamine to alleviate the symptoms of Parkinson's disease.
Step-by-step explanation:
The combo drug carbidopa-levodopa is used in the treatment of Parkinson's disease. Carbidopa is a medication that helps prevent the breakdown of levodopa in the bloodstream before it reaches the brain.
Levodopa is converted into dopamine in the brain, helping to alleviate the symptoms of Parkinson's by increasing dopamine levels. Therefore, the role of the combo drug carbidopa-levodopa is to provide the brain with levodopa, which can be converted into dopamine to compensate for the loss of dopaminergic neurons in Parkinson's disease.