A new British analysis found that Avandia and Actos, two widely prescribed diabetes drugs, could double their risk of bone fractures. Avandia (rosiglitazone), manufactured by GlaxoSmithKline PLC, and Actos (pioglitazone), manufactured by Takeda Pharmaceuticals North America Inc., are both part of the same class of medications, known as thiazolidinedione agents.

An analysis carried out at the Wake Forest University School of Medicine in North Carolina assessed the increased fracture risk of both drugs. Moreover Avandia is already well known to significantly raise the risk of heart attacks. The study found no increased risk of fractures among men.

The new study, which was published online December 9, 2008, by the Canadian Medical Association Journal, involved data on 14,000 patients from 10 prior drug trials. "This study shows that these agents double the risk of fractures in women with type 2 diabetes, who are already at higher risk before taking the therapy," said Sonal Singh of North Carolina's Wake Forest University School of Medicine.

Scientists already knew the two thiazolidinedione (TZD) drugs for diabetes were associated with fractures, but the magnitude of the risk had not been evaluated. There is no clear evidence that other drugs used to treat type 2 diabetes, such as metformin and sulfonylurea, cause an increased risk of fractures as well.

Researchers said the underlying cause of the sex-specific effect of TZDs on fractures was unclear, but they suggested the drugs may cause the problem by replacing bone marrow with fat cells, according to Reuters. However women should not stop taking the drugs without first taking medical advice.

Nevertheless GlaxoSmithKline, which markets rosiglitazone as Avandia, explained that the safety and effectiveness of the drug was backed by one of the largest clinical trial programmes ever undertaken for any medicine, with 52,000 patients studied.