TUESDAY, Dec. 11, 2007 (HealthDay News) -- Older patients using the diabetes drug Avandia faced an increased risk of heart attack, heart failure and even death, new research shows.
According to the Canadian authors of the study, which is published in the Dec. 12 issue of the Journal of the American Medical Association, this is the first population-based look at the class of drugs to which Avandia belongs and the first report to find an increase in mortality rates.
"Our study looked at an older population in the real world who tend to be underrepresented in research trials and are at higher risk," said study author Dr. Lorraine L. Lipscombe, a researcher with the Institute for Clinical Evaluative Sciences in Toronto. "While the overall risk versus benefit is difficult to interpret in all people, in older people, the risks may outweigh the benefit."
"This is very striking data," added Dr. Steven Nissen, chairman of the department of cardiovascular medicine at the Cleveland Clinic Foundation. "This and other studies are going to put tremendous pressure on the FDA [U.S. Food and Drug Administration] to act more forcefully with regard to Avandia."
But the maker of Avandia (rosiglitazone), GlaxoSmithKline, took issue with the findings.
In a prepared statement, the company said the Canadian study "has significant limitations and generates misleading conclusions regarding acute myocardial infarction and death. These conclusions are inconsistent with a more robust body of evidence from large, long-term, prospective, well-designed clinical studies, including ADOPT and RECORD. These long-term trials in diabetic patients comparing rosiglitazone to other oral anti-diabetic medicines show no increased risk for cardiovascular events compared to other commonly used medications, other than the well-known risk of congestive heart failure with thiazolidinedione (TZDs)."
Nissen was the first scientist to publish concerns about Avandia and increased heart risks in a study last May.
After that and other research was released, the FDA added a "black box" warning to all drugs in the class. An FDA advisory panel voted against removing the drug from the market, citing inconclusive evidence.
The Canadian label for Avandia carries a stronger message: The drug is not to be used as the sole medication for type 2 diabetes unless the patient cannot take another drug to lower blood sugar and that the drug should not be used by any patient with heart failure.
People with type 2 diabetes are already at heightened risk for cardiovascular disease.
Thiazolidinediones including Avandia and Actos (pioglitazone) heighten the body's sensitivity to insulin. Some 3.5 million U.S. patients take Avandia, which has also been linked to bone loss in some patients.
The current study involved an older (66 and over), "real-world" population consisting of more than 159,000 residents of Ontario in this age group who were treated with at least one oral diabetic medication. The patients were followed for about four years.
Compared to individuals taking more than one oral hypoglycemic agent, people using Avandia on its own had a 60 percent increased risk of congestive heart failure, a 40 percent increased risk of heart attack, and a 29 percent increased risk of dying.
The increased risks were associated with Avandia only, but fewer people in the study took Actos, so the results could be skewed, the researchers noted.
"It looks like the results were limited to Avandia, but 50 percent fewer people were on Actos, so you can't rule out an increased or decreased risk with Actos," Lipscombe said. "We need more studies."
"It's an observational study and, like all observational studies, this has strengths and weaknesses. These studies do not provide the strength of evidence of a prospective, randomized trial," Nissen pointed out. "But as observational studies go, this one is very helpful, because it is quite large, and it is independent, not sponsored by any company. Remarkably, with Avandia, the increased risk of heart attack is very similar to what we reported in our meta-analysis last May."
In related research appearing in the same issue of JAMA, a review of 25 studies found that current smokers have a 44 percent increased risk of developing type 2 diabetes compared with nonsmokers.
The degree of risk was linked to the level of smoking -- there was a 61 percent increased risk for those smoking 20 or more cigarettes a day and a 29 percent increased risk for those who smoked less, said the Swiss researchers. Former smokers had a 23 percent increased risk.
For more on diabetes drugs, visit the U.S. Food and Drug Administration.