Bisphosphonates approved for the treatment of osteoporosis will now bear a label warning about the risk for 2 types of atypical femur fractures, the US Food and Drug Administration (FDA) announced today.

One type of break, subtrochanteric femur fracture, occurs just below the hip joint. Another type, diaphyseal femur fracture, is in the long part of the bone. Both are very uncommon, accounting for less than 1% of all hip and femur fractures overall, according to the agency.

Risedronate sodium, alendronate

The FDA's decision to add a warning about the fractures to the labels of bisphosphonates comes in the wake of a recommendation to do so by a task force of the American Society for Bone and Mineral Research. In a report released last month, the task force said that of 310 cases of atypical femur fractures under study, 94% of the patients had been taking bisphosphonates, most for more than 5 years. The task force stopped short of declaring that the medications cause the fractures.

The label change applies only to bisphosphonates approved for osteoporosis such as alendronate (Fosamax®; Merck) and risedronate sodium (Actonel®; Proctor & Gamble Pharmaceuticals). Bisphosphonates approved for the treatment of Paget's disease and high blood calcium levels caused by cancer are unaffected.

More information about the announcement is available on the FDA's Web site.

To report adverse events related to bisphosphonates, contact MedWatch, the FDA's safety information and adverse event reporting program, by telephone at 1-800-FDA-1088, by fax at 1-800-FDA-0178, online at http://www.fda.gov/medwatch, or by mail to MedWatch, FDA, 5600 Fishers Lane, Rockville, Maryland 20852-9787.

Robert Lowes • Medscape Medical News © 2010 WebMD, LLC