Outlook on diabetes drug less than rosy

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In May 2007, millions of people with diabetes got something extra to worry about - the possibility that a drug they were taking to control blood sugar might be harming their hearts. According to a report in the New England Journal of Medicine (NEJM) that touched off a media firestorm, Avandia (rosiglitazone) increases the chances of having a heart attack or dying of cardiovascular disease. The news prompted many people to call their doctors.

The cardiovascular safety of Avandia and other diabetes drugs is an important issue, since heart disease is the most common cause of death among people with diabetes. More than 16 million Americans have the disease, and the number is growing fast. The preliminary finding certainly sounds a note of caution about this new drug.

Controlling blood sugar

Type 2 diabetes often starts when the body's tissues lag in responding to insulin. This hormone unlocks the molecular doors through which blood sugar enters a cell.

Resistance to insulin means that sugar builds up in the bloodstream after a meal or snack, instead of being efficiently and relatively rapidly absorbed by cells to meet their energy needs. The body responds by making extra insulin in an effort to force open those doors.

Avandia makes liver and muscle cells more sensitive to insulin. The FDA approved the drug in 1999 based on clinical trials showing that it reduces blood sugar levels in people with type 2 diabetes.

That's a good thing, and it is the most immediate goal of diabetes drugs. But none of the trials lasted long enough to show if Avandia prevents what actually matters to people with diabetes - heart disease, damage to blood vessels or nerves, or cardiovascular-related death.

Some early signs hinted at problems with the drug. It can increase LDL (bad) cholesterol by 15% to 20% and slightly reduce the amount of oxygen-carrying haemoglobin. Bothered by these and other hints of trouble, two Cleveland Clinic researchers combed the results of 42 clinical trials that tested Avandia against a placebo for cardiovascular problems.

After adjusting for age, level of diabetes, how long the medication was taken, and other factors, the researchers determined that those taking rosiglitazone had a 43% higher risk of having a heart attack and a 64% higher risk of dying from cardiovascular disease.

Keep in mind that those are relative risks - they compare problems with Avandia against problems with placebo. The absolute risks are a bit more reassuring. Among the 15,560 volunteers who took Avandia, 86 (0.55%) had heart attacks and 39 (0.25%) died. Among the 12,283 who took a placebo, 72 (0.58%) had heart attacks and 22 (0.18%) died. It is also worth noting that none of the trials included in this study were designed to look at the drug's effect on the heart.

A large trial that began in 2000, Rosiglitazone Evaluated for Cardiac Outcomes and Regulation of Glycemia in Diabetes (RECORD), is looking specifically at the cardiovascular impact of the drug. A week after the NEJM report appeared, the journal published a midstream analysis of RECORD conducted by the independent board that monitors the trial for safety. It didn't show a big hazard with Avandia, but it didn't show a cardiac benefit from the drug, either.

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