This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Other topics and Adverse effects, Subject name: Anatomy
[{'content': 'Which of the following drugs is a full agonist at opioid receptors, has excellent oral bioavailability, analgesic equipotency to morphine and a longer durationlof action with milder withdrawal symptoms on abrupt discontinuation? \nSelect and explain. \nA. Fentanyl, B. Hydromorphone, C. Methadone, D. Nalbuphine', 'role': 'user'}, {'content': 'Answer: C \nExplanation: (Ref: KDT 6/e p459, 460) Methadone is a long acting opioid agonist that has equal potency to morphine. It can be used orally for opioid replacement and opioid rotation therapy. Due to longer half life, it produces mild withdrawal symptoms.', 'role': 'assistant'}]