This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Opioids, Subject name: Pharmacology
[{'content': 'Opioid agonist-antagonist is : \nSelect and explain. \nA. Pethidine, B. Pantazocine, C. Buprenorphine, D. Methadone', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' Pentazocine Opioid Agonist Antagonists Not used as analgesic - Nalorphine* levallorphan* Used as analgesic - Pentazocine* NalbuphinePure Opioid Antagonists :NaloxoneNaltrexonePartial weak agonistsBuprenorphineButorphanol", 'role': 'assistant'}]