Which of the following is a first generation sulfonylurea?

• A. Gliclazide
• B. Chlorpropamide
• C. Glipizide
• D. Metformin

Answer: (B)

First-generation sulfonylureas are the older drugs in this class, historically used to boost insulin release by closing the ATP-sensitive potassium channels on pancreatic beta cells, which depolarizes the cell and triggers insulin release. Among the options, chlorpropamide is the one that belongs to this early group, making it the correct example of a first-generation sulfonylurea. The other drugs listed fit into different generations or classes: metformin is a biguanide, while gliclazide and glipizide are second-generation sulfonylureas. (Second-generation sulfonylureas are typically more potent and have different side-effect profiles compared with the first generation.)