This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anaesthesia, Subject name: Pharmacology
Methemoglobinemia is caused by: 
Select and explain. 
A. Prilocaine, B. Ropivacaine, C. Bupivacaine, D. Procaine
A: Prilocaine
Answer: A: Prilocaine 
Explanation: Ans. (A) Prilocaine(Ref: Katzung 11th/e p449)The administration of large doses (>10mg/kg) of prilocaine during regional anesthesia may lead to accumulation of the metabolite o-toluidine, an oxidizing agent capable of converting hemoglobin to methemoglobin.The treatment of methemoglobinemia involves the intravenous administration of reducing agents (eg. methylene blue or ascorbic acid), which rapidly convert methemoglobin to hemoglobin.