This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: A.N.S., Subject name: Pharmacology
The unknown drug is likely to be: 
Select and explain. 
A. Low dose adrenaline, B. High dose adrenaline, C. Nor-adrenaline, D. Isoprenaline
B: High dose adrenaline
Answer: B: High dose adrenaline 
Explanation: Ans. (B) High dose AdrenalineGiven figure shows that after giving a drug, blood pressure first increases and then decreases. It is known as biphasic response which is characteristic of high dose adrenaline. At low doses, adrenaline stimulates only beta 2 receptors and thus cause only fall in BP. But at high doses, it stimulates both alpha and beta receptors and initially cause rise in BP due to alpha receptor stimulation, however as plasma concentration falls, it lead to decrease in BP due to stimulation of only beta 2 receptors. This is known as biphasic response