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: Pharmacology
[{'content': 'Which of the following drug is most commonly used world wide in maintenance doses for opioid dependence? \nSelect and explain. \nA. naltrexone, B. Methadone, C. Imipramine, D. Disulfiram', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e., Methadone Methodone maintenance is the most common form of pharmacoligical treatment for opioid dependence.", 'role': 'assistant'}]