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': 'Prior to general anesthesia and surgery which oral hypoglycemic drug should be discontinued? \nSelect and explain. \nA. Piglitazone, B. Metformin, C. Glybenclamide, D. Glyclazide', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]