Taking drugs to prevent bone breakage may actually increase the chances for an unusual type of thigh bone fracture, Food and Drug Administration officials warned Wednesday.

The drugs, used by millions of women, known as bisphosphonates which are in Merck & Co Inc's Fosamax, Roche Holding AG's Boniva, Novartis AG's Reclast and Warner Chilcott Plc's Actonel.

The FDA is not clear whether the bisphosphonates are the primary cause of the fractures.

The fractures were however predominantly reported in patients who were taking bisphosphonate medications.

The FDA warning "should not cause patients taking bisphosphonates to be fearful of their medicine," said FDA new drugs office deputy director, Dr. Sandra Kweder.

The drugs "are an important mainstay of osteoporosis management" and "have prevented innumerable fractures in their years of use," Kweder said.

According to the FDA, more than 5 million U.S. patients filled prescriptions for bisphosphonates in 2009.

Bone fractures from osteoporosis occur mainly in the hip, wrist or spine.

Published by Medicaldaily.com