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': 'Opioid with monoamine action is? \nSelect and explain. \nA. Tramadol, B. Pentazocine, C. Pethidine, D. Meperidine', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., Tramadol Unlike other opioids, tramadol inhibits reuptake of NA and 5-HT and thus activates monoaminergic spinal inhibition of pain --> action can be abolished by 5-HT3 antagonist (ondansetron).", 'role': 'assistant'}]