This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Psychiatry
[{'content': 'The drug which is used for long-term maintenance in opioid addiction - \nSelect and explain. \nA. Naloxone, B. Nalorphine, C. Butarphanol, D. Methadone', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Drugs for long-term maintenance for opioid dependence (addiction) :- Methadone is the DOC. Alternatives are buprenorphine, LAAM, opioid antagonists (naltrexone).', 'role': 'assistant'}]