A new study indicates that drugs called thiazolidinediones used to control blood sugar in patients with type 2 diabetes may do more harm than good. Scientists report in the Canadian Medical Association Journal (CMAJ) that women who take the meds have reduced spine and hip bone density and have double the risk of fracturing bones if they're on the pills for more than a year.

"When you weigh the good and the bad, there is no reason to use these drugs," says study co-author Curt Furberg, a public health scientist at Wake Forest University School of Medicine in Winston-Salem, N.C. "There are other drugs for [type 2] diabetes that are better," he added, noting that thiazolidinediones have also been linked to heart failure. 

Diabetes type 2 is a disease in which the body begins to ignore or fails to produce enough insulin, the hormone cells need to absorb glucose, their primary fuel source. If muscles and other tissues cannot absorb glucose from the blood, nerve and blood vessel damage ensues, which can lead to variety of life-threatening complications including heart disease, stroke, and infections. This form of diabetes is most common in people who are overweight and over the age of 40.

There are about 180 million people living with diabetes worldwide. Some 162 million (90 percent) of these patients have the type 2 variety. Four million Americans are currently taking thiazolidinediones, which lower blood sugar by reducing a person's insulin resistance.

Furberg and his colleagues reached their conclusions based on a review of 10 studies involving nearly 14,000 men and women with type 2 diabetes taking thiazolidinediones; only the women were found to have an increased risk of bone breaks.

The Food and Drug Administration (FDA) approved the two commonly used thiazolindinediones, rosiglitazone (Avandia) and pioglitazone (Actos), for use in 1999. Furberg says the agency tends to approve diabetes drugs based on their ability to lower blood sugar, but notes this may not be the best barometer for assessing a drug's value. "New research suggests that lowering blood sugar too much might cause complications," he says, noting, for example, that recent studies suggest that both rosiglitazone and pioglitazone double patients' heart attack risk.  "The whole field [of diabetes drug research] is up in the air."

Furberg believes all patients should talk to their doctors about switching to one of several alternatives on the market with fewer potential side effects. He favors a drug called metformin, which also lowers insulin resistance. It has some potential side effects, including indigestion and allergic reactions, but he says they are less dangerous than those of the thiazolindinediones. "Metformin is safer than the others," he says. "For now, it's the best we have."
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