This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Drugs, Subject name: Medicine
Which of the following is the most likely reason why fentanyl does not disturb cardiovascular stability as much as morphine? 
Select and explain. 
A. is water soluble, B. is lipid soluble, C. does not stimulate histamine release, D. is long acting
C: does not stimulate histamine release
Answer: C: does not stimulate histamine release 
Explanation: Morphine releases histamine and can cause cardiovascular instability. Fentanyl does not release histamine, and causes only mild decreases in heart rate and blood pressure. Fentanyl, a lipid-soluble drug, has an elimination half-life between 3 and 4 hours. It is 100 times more potent than morphine.