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 opioid analgesic acts primarily through K opioid receptors? \nSelect and explain. \nA. Pentazocine, B. Methadone, C. Buprenorphine, D. Pethidine', 'role': 'user'}, {'content': 'Answer: A \nExplanation: (Ref: KDT 6/e p464, 465) Pentazocine can cause dysphoric reactions (hallucinations) by stimulating the K receptors.', 'role': 'assistant'}]