Oral Diabetes Medications

Thiazolidinediones

Pioglitazone (Actos) and rosiglitazone (Avandia) are the two thiazolidinediones currently available. They work by decreasing the body's resistance to the actions of insulin. Since obese people with diabetes are insulin resistant, they are often treated with Actos or Avandia.

One welcome outcome of treatment is redistribution of body fat from around the midsection. However, thiazolidinedione drugs often cause an overall weight gain due partly to fluid retention, which can lead to heart failure or worsen existing heart failure. As a result, thiazolidinediones aren't recommended for people with heart failure.

Further concerns were raised with a review of studies on Avandia, which found that the drug was associated with an increased chance of heart attacks compared with other diabetes treatments. The FDA's review of Avandia and the risk of heart attack is ongoing.

Liver failure was a rare but catastrophic effect of the first thiazolidinedione to be approved, troglitazone (Rezulin), prompting it to be withdrawn from the market. Cases of liver failure have not been reported with Actos or Avandia, but the FDA still requires blood testing to measure liver function during the first year of treatment.

Thiazolidinediones are used alone or in combination with a sulfonylurea, a meglitinide, metformin, an alpha-glucosidase inhibitor, or insulin. When a thiazolidinedione is added to insulin, it may take up to eight weeks before the full effects are seen. So it's important to check frequently for hypoglycemia, which signals the need to decrease the insulin dosage. People who take the cholesterol-lowering medications cholestyramine (Questran, Questran Light) or colestipol (Colestid) should be aware that these drugs inhibit the absorption of thiazolidinediones and should not be taken at the same time of day.

Publication Review By: Written by: Christopher D. Saudek, M.D.; Simeon Margolis, M.D., Ph.D.

Published: 21 Apr 2009

Last Modified: 10 Mar 2015