Diabetes drug Avandia (rosiglitazone) is significantly more effective than older, cheaper drugs metformin and glyburide in delaying the progressive loss of blood sugar control in newly diagnosed type 2 diabetics, according to data presented Dec. 4th at the World Diabetes Congress in Cape Town.

A study that tracked patients for up to five years, conducted at 300 centers in North America and Europe, showed that diabetics who were started on Avandia were 32 percent less likely to need to add a second drug than those started on metformin, and 63 percent less likely than those started on glyburide.

"This is the first long-term study to demonstrate that the progressive loss of blood sugar control can be delayed and target blood sugar levels can be maintained for a longer period with rosiglitazone than with metformin and glyburide -- the two most frequently prescribed oral antidiabetic agents," said Dr. Steven Kahn, a professor at the University of Washington School of Medicine in Seattle.

The primary reasons for loss of blood sugar control are increasing insulin resistance and declining beta-cell function. Avandia is an insulin-sensitizing drug, one of a newer new class of drugs that help insulin work better in patients with type 2 diabetes.

ADOPT demonstrated that Avandia significantly improved insulin sensitivity compared to metformin or glyburide, and reduced the rate of loss of beta-cell function.

"The more durable effect on blood sugar with rosiglitazone was also consistent with greater improvements in core defects of the disease, including significant effects on insulin resistance and beta-cell function," added Kahn.

On the negative side, however, Avandia was associated with more weight gain, fluid retention (which can exacerbate or lead to heart failure), and surprisingly a higher incidence of fractures most commonly involving the foot and upper limbs.

The results of this international study called ADOPT (A Diabetes Outcome Progression Trial) involving 4,360 people were published today in the New England Journal of Medicine.

In an editorial in the New England Journal, Dr. David Nathan of Harvard Medical School said what he called the "modest" benefit of Avandia and its higher cost meant that metformin remained the logical choice when initiating treatment of type 2 diabetes.