This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pharmacology
L-Dopa is combined with carbidopa in the treatment of parkinsonism to - 
Select and explain. 
A. Decrease the efficacy of levodopa, B. Decrease the efficacy of levodopa, C. Increase the dose of levodopa required, D. Inhibit conversion of levodopa to dopamine in the CNS
B: Decrease the efficacy of levodopa
Answer: B: Decrease the efficacy of levodopa 
Explanation: Ans. is 'b' i.e., Inhibit peripheral decarboxylation of levodopa Carbidopa is combined with levodopa to inhibit peripheral decarboxylation of levodopa and make more levodopa available to cross the blood brain barrier to reach its site of action.