Certain diabetes drugs found to double bone fracture risk in women

Diabetic women are already at a higher than normal risk of fractures, experts said, so a doubling of risk could have a substantial effect.

Researchers had known there was an increased risk of fractures associated with the drugs, but not the magnitude of the risk, said Dr. Sonal Singh of Wake Forest University School of Medicine. Singh led the new study, reported online Wednesday in the Canadian Medical Assn. Journal.

Use of the drugs for at least a year in women older than 70 would result in at least one additional fracture among every 21 women, Singh and colleagues reported.

The drugs would produce an additional fracture for every 55 women between the ages of 55 and 70, they said.

As estimated 4 million Americans take the drugs, about half of them women, researchers said. Rosiglitazone is sold under the brand name Avandia by GlaxoSmithKline. Pioglitazone is sold as Actos by Takeda Pharmaceutical Co.

The researchers combined results from 10 clinical trials that included 13,717 diabetics. They found that the drugs reduced bone density in the spine and hips of the elderly women, increasing the risk of fractures.

The exact mechanism of bone weakening is not known, but the researchers speculated that the drugs cause bone marrow to be replaced with fat cells.

"This evidence adds to the growing concern regarding these drugs, which have also been associated with a higher risk of heart failure and possibly heart attacks," wrote Dr. Lorraine Lipscombe of the University of Toronto in an editorial accompanying the report. "Because diabetes drugs are typically approved based on their effects on sugar control rather than long-term outcomes, these adverse effects have only emerged after the drugs have been on the market."

Maugh is a Times staff writer.

thomas.maugh@latimes.com