People who take bisphosphonate drugs to treat osteoporosis need to be aware of a rare type of thigh bone fracture, U.S. health officials say.

The U.S. Food and Drug Administration warned patients and health-care professionals Wednesday about a rare type of fracture reported mainly in patients taking prescription drugs such as Fosamax that slow or stop loss of bone mass.

The fractures occur just below the hip joint or in the long part of the thigh.

"We know from clinical trials that these drugs do prevent the common osteoporosis fractures," said Dr. Sandra Kweder, FDA's deputy director for new drugs. "The fractures we're talking about today are very unusual and rare."

The fractures appear to account for less than one per cent of all hip and femur, or thigh bone, fractures overall, the FDA said.

Label changes

The notice applies to bisphosphonates approved to treat osteoporosis, including: Merck & Co.'s Fosamax and Fosamax Plus D; Procter & Gamble Co.'s Actonel and Actonel with Calcium; Roche's Boniva; Warner Chilcott's Atelvia; Novartis's Reclast; and their generic versions.

People who currently take a bisphosphonate are advised to:

• Continue to take your medication unless you are told to stop by your health-care professional.
• Talk to your health-care professional if you develop new hip or thigh pain (commonly described as dull or aching pain), or have any concerns with your medications.
• Report any side-effects with your bisphosphonate medication to regulators.

More than five million prescriptions for the drugs were written last year, according to the FDA. The drug is mainly prescribed to women after menopause.

The FDA said new warning and precautions information will be added to the product labels. Also, a medication guide included with all bisphosphonate medications approved for osteoporosis will better inform patients of the risk.

Health Canada said it considers the benefits of bisphosphonate to outweigh the risks when used as directed. If the department's current review identifies new safety information then it will act and inform Canadians.

Two weeks ago, national class-action lawsuits were launched regarding unexplained broken thigh bones among Canadians taking bisphosphonates. The suits apply to everyone who has been taking the medications, said lawyer Tony Merchant.

Two suits seek damages for people who've sustained a fracture. They also call for medical monitoring for everyone who has taken the drugs to check for nodules that may form.

None of the suits have been certified and none of the claims have been proven.

With files from The Associated Press