This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General pharmacology, Subject name: Pharmacology
All these EXCEPT one cross the blood-brain barrier: 
Select and explain. 
A. Morphine, B. Dopamine, C. Propranolol, D. Ether
B: Dopamine
Answer: B: Dopamine 
Explanation: Dopamine does not cross BBB. Hence it is administered as levodopa levodopa is the prodrug which is conveed to dopamine in the brain Pg.no.425 K D Tripathi Seventh edition