A class of oral diabetes drugs, commonly nicknamed “glitazones.” Unlike the traditional oral drugs called sulfonylureas, which lower blood glucose levels by making the pancreas secrete more insulin, the thiazolidinediones work by helping the body’s tissues to use insulin more effectively and by suppressing glucose production by the liver.

The first thiazolidinedione to become available in the United States, troglitazone (brand name Rezulin), was withdrawn from the U.S. market in March of 2000 because its use was associated with liver toxicity and death. Since then, two newer thiazolidinediones called pioglitazone (Actos) and rosiglitazone (Avandia), have become available. Their use has not been associated with liver toxicity, but anyone taking them must have frequent liver function tests to make certain they aren’t harming the liver.