Diabetes Drug Linked to Fracture Risk

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Data from multiple studies have shown that taking the Type 2 diabetes drug rosiglitazone (brand name Avandia) may put women at higher risk for a variety of bone fractures.

Rosiglitazone, a member of the class of oral diabetes drugs called thiazolidinediones, helps people control their diabetes in two ways: by making the body’s tissues more sensitive to insulin and by causing the liver to release less glucose into the bloodstream. In addition to being sold as the stand-alone drug Avandia, rosiglitazone is found in Avandamet (a combination of rosiglitazone and metformin) and Avandaryl (a combination of rosiglitazone and glimepiride, a sulfonylurea drug).

The first study, published in The New England Journal of Medicine on December 7, 2006, randomly assigned 4,360 people newly diagnosed with Type 2 diabetes to drug therapy with either rosiglitazone, metformin, or glyburide (a sulfonylurea). Neither the researchers nor the participants knew who had received which drug. The researchers followed the participants for 4-6 years. The main point of the study was to compare blood glucose control achieved by using the different drugs.

The study showed that participants who took rosiglitazone maintained blood glucose control for the longest period of time without the need for additional medicines. However, it also showed that women who took rosiglitazone experienced significantly more fractures of the upper arm, hand, or foot than those who took the other drugs. (Men in all three drug groups experienced similar rates of fracture.) Then, an independent analysis of another large-scale trial of rosiglitazone currently in progress confirmed a higher risk of these fractures among women taking that drug.

These results prompted the U.S. Food and Drug Administration (FDA) and rosiglitazone manufacturer GlaxoSmithKline to release a warning letter in February informing health-care providers of the potential increased risk of fractures in women who take the drug. The letter points out that the mechanism by which the drug is linked to fracture risk is unclear. It also points out that the fracture sites observed in the study are not the same as those associated with postmenopausal osteoporosis (a degenerative bone disease), the hip and spine.

However, a smaller, shorter-term study did link rosiglitazone with a potential increase in risk for hip fractures. That study, published on January 30 in The Journal of Clinical Endocrinology and Metabolism, took place in New Zealand and enrolled 50 postmenopausal women. The women—none of whom had diabetes—were randomly assigned to take rosiglitazone or a placebo (dummy pill). Over the course of 14 weeks, the researchers looked at markers of bone formation and bone density in both groups of women. Neither the researchers nor the participants knew who had received the drug and who had received the placebo.

The researchers found that hip bone density decreased significantly more in women who took rosiglitazone than in those who took a placebo. Markers of bone formation also decreased in the rosiglitazone group. These results led the researchers to conclude that rosiglitazone may increase the risk of osteoporosis and related hip fractures by inhibiting bone formation and speeding up bone loss.

While more research is needed in this area, GlaxoSmithKline admits that “the risk of fracture should be considered” by people with diabetes and their health-care providers when deciding whether to begin or continue drug therapy with rosiglitazone.

For more information about diabetes and your bones, please see the article “Boning Up on Bone Health.”

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