Sulfonylureas are used almost exclusively in type 2 diabetes. Other types of diabetes generally do not respond to sulfonylurea therapy. These drugs should not be used for gestational diabetes.
Although for many years sulfonylureas were the first drugs to be used in new cases of diabetes, in the 1990s it was discovered that obese patients might benefit more from metformin.
In about 10% of patients, sulfonylureas alone are ineffective in controlling blood glucose levels. Addition of metformin or a thiazolidinedione may be necessary, or (ultimately) insulin. Triple therapy of sulfonylureas, a biguanide (metformin) and a thiazolidinedione is generally discouraged, but some doctors prefer this combination over resorting to insulin.
Sulfonylureas, as opposed to metformin and the thiazolidinediones, can induce hypoglycemia when insulin production overshoots. It is treated with sugary food, or (in the case of hypoglycemic coma) with intravenous dextrose. The best way to prevent this side effect is to choose the lowest possible dose that adequately controls glucose levels.
Like insulin, sulfonylureas can induce weight gain. Other side effects can include abdominal upset, headache and hypersensitivity reactions.
Sulfonylureas can potentially cause birth defects, and cannot be used in pregnancy or in patients who intend to get pregnant. Impairment of liver or kidney function increase the risk of hypoglycemia, and are contraindications. As other anti-diabetic drugs cannot be used either under these circumstances, insulin therapy is the only option in pregnancy and hepatic and renal failure.
Second-generation sulfonylureas have increased potency by weight, compared to first-generation sulfonylureas. They have decreased side effects but are more expensive.