The consumer watchdog group Public Citizen is claiming that five years ago, the Food and Drug Administration knew that the diabetes drug Avandia carried a risk of congestive heart failure. The group cites a 2002 internal memo in which agency reviewers urged that a warning about Avandia’s heart failure risk should be added to its labeling.

Avandia is meant to treat type 2 diabetes by helping the body more efficiently utilize the insulin it produces. The FDA memo in question says that patients taking it may be more likely to suffer congestive heart failure.

Disclosure of this memo by Public Citizen follows closely upon a New England Journal of Medicine article that links Avandia to a greater risk of heart attacks and heart-related deaths. Researchers, led by Dr. Steven Nissen of the Cleveland Clinic, analyzed the data of almost 28,000 patients involved in 48 studies. They determined that people taking Avandia were 64% more likely to die of heart problems and 43% more likely to suffer heart attacks than other patients.

Dr. Sidney Wolfe of Public Citizen wrote a letter to FDA Commissioner Andrew von Eschenbach. In it, he asked the agency to add a “black-box” warning to Avandia or to go further and issue a complete Avandia recall. Dr. Wolfe claims that safer and equally effective diabetes drugs are already on the market. Because of this and the risk of Avandia side effects, it should not be prescribed to patients, he says.

The FDA has reacted cautiously to the well-publicized article in the NEJM. It announced plans for an advisory committee to study Avandia and its side effects. No Avandia recall has been issued or planned, but the agency has advised patients to speak with their doctors about other ways of treating their diabetes.