This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Central Nervous system, Subject name: Pharmacology
Naltrexone is used to maintain abstinence following opioid withdrawal in addicts.It blocks all of the following features of opioid use, except: 
Select and explain. 
A. Euphoriant effects of opioids, B. Craving for opioids, C. Miosis, D. Respiratory depression
B: Craving for opioids
Answer: B: Craving for opioids 
Explanation: Naltrexone, is a medication primarily used to manage alcohol or opioid dependence. An opioid-dependent person should not receive naltrexone before detoxification. It is taken by mouth or by injection into a muscle. Effects begin within 30 minutes. Ref: KD tripathi 8th ed.