This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Substance abuse, 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: Maintenance Therapy After the detoxification phase is over, the patient is maintained on one of the following regimens: 1. Methadone maintenance (Agonist substitution therapy) 2. Opioid antagonists Opioid antagonists have been in use for a long time but they were either paial antagonists (such as nalorphine) or had to be administered parenterally (such as naloxone) Ref: A Sho Textbook of Psychiatry, Niraj Ahuja, 7th Edition, pg. no. 44', 'role': 'assistant'}]