Blood-Thinner Linked To Osteoporotic Fractures

The long-term use of warfarin, a drug commonly prescribed to reduce the risk of blood clots, appears to increase the risk of fractures associated with osteoporosis, a bone-thinning condition that usually increased with age, according to a report. As the study authors note, warfarin prevents coagulation by blocking vitamin K, which is needed to activate certain clotting factors. Because vitamin K is also used to activate proteins involved in bone formation, drugs like warfarin may increase the risk of fractures, the researchers report in the Archives of Internal Medicine. To investigate, Dr. Brian F. Gage, from Washington University School of Medicine in St. Louis, and colleagues assessed the rate of osteoporotic fractures among 12,048 Medicare beneficiaries. The subjects included 4,461 who had been prescribed warfarin for at least one year and 7,587 who were not on the drug. Warfarin users were 25 percent more likely to experience a fracture than nonusers, the report indicates. However, this relationship was statistically significant only in men. Further analysis of data from 1,833 patients who were on warfarin for less than one year did not detect a statistically significant increase in fracture risk. Risk factors for fracture included older age, high risk of falling, overactive thyroid, neurological or psychiatric disorders, and alcoholism, the report notes. By contrast, African American race, male gender, and the use of beta-blocker drugs were associated with a decreased risk of fracture. The reason for the apparent protective effect of beta-blockers is not known, the team comments, although animal studies have indicated that beta-blockers increase bone mass. Meanwhile, the researchers advise, "When prescribing warfarin to elderly patients at high risk of falling, healthcare providers can instruct them to wear stable shoes, exercise regularly, have adequate intake of calcium and vitamin D, use walking aids, and discontinue unnecessary medications." SOURCE: Archives of Internal Medicine, January 23, 2006.