Definition: Sulfonylureas are a classification of oral medication used to treat type 2 diabetes. These medications are the oldest of the oral drugs. Tolinase (tolazamide) has been around since the 1950s. It's still prescribed today. Newer drugs in this class include Glucotrol (glipizide), Glucotrol XL (glipizide extended release), Amaryl (glimepiride), Diabeta (glyburide), and Micronase (glyburide). They're hypoglycemic agents because they allow the pancreas to release more insulin into the blood, which lowers the glucose level. Hypoglycemia is a common side effect.