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
[{'content': 'Naltrexone is used for which of the following function in opioid addiction? \nSelect and explain. \nA. prevention of relapse, B. Treatment of withdrawal, C. Treatment of overdose, D. Prevention of withdrawal', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Naltrexone is a pure opiod antagonist. It is used for opiod blockade theory in post addicts mainly for maintainence therapy and mathadone for substitution therapy. Ref: KD Tripati 8th ed.', 'role': 'assistant'}]