This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anesthesia, Subject name: Pharmacology
[{'content': 'Mehemmoglobinemia is caused by \nSelect and explain. \nA. Prilocarpine, B. Ropivaciane, C. Bupivacaine, D. Procaine', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Refer Katzung 11/e p449. The admistration of large doses of prilocarpine during regional anesthesia may lead to accumulation of the metabolite o-toludine an oxidizing agent capable of conveing hemoglobin to methemoglobin', 'role': 'assistant'}]