Can osteoporosis medications cause bone fractures?

DEAR DOCTOR K:

I’m taking a pill for osteoporosis because my doctor says that stronger bones will reduce my risk of fractures. But a friend recently told me that some osteoporosis medicines actually cause fractures. Can you un-confuse me?

DEAR READER:

I know what you’re referring to, and it is confusing — even for doctors. So let me try to make it less confusing.

Osteoporosis does make your bones more susceptible to fractures, and a group of drugs called bisphosphonates do successfully treat osteoporosis. These drugs include alendronate (Fosamax), ibandronate (Boniva), risedronate (Actonel) and zoledronic acid (Reclast). People typically remain on these drugs for years.

There is no doubt that these drugs work. They slow and even reverse the thinning of bones. They reduce the risk of common fractures, such as hip fractures, by 50 percent or more.

However, paradoxically, these medicines can cause two rare types of fractures: a fracture of the jaw and fractures of the middle of the thigh bone. That’s particularly true in people taking bisphosphonate drugs for a long time.

How long should the drugs be taken? They definitely reduce common fractures in people taking them for three to five years. There is no strong evidence that they continue to work if continued beyond five years, but it’s reasonable to believe that they might.

After talking with my colleagues here at Harvard Medical School who are experts on this question, here’s what I’m telling my patients. If a person has a relatively high risk for developing a common type of hip fracture (which involves the upper part of the thigh bone) or a fracture of the vertebrae (bones of the spine), he or she should stay on the drugs. If the risk is relatively low, he or she should consider going off the drugs after five years.

You can estimate your risk of fractures by using a tool from the World Health Organization called FRAX. The FRAX tool includes information about you, including the T score of your bone density test. The T score compares the density of your bone to the bone of the average young adult. (I have information about the FRAX on my website, AskDoctorK.com.)

 

Understanding FRAX: How likely are you to break a bone?

To boil it down, I am telling my patients that if they have been on bisphosphonates for less than five years, stay on them. On the other hand, if they’ve been on the medicines for five years or more and they have:

  • a T score that is lower than minus-2.5 at the hip, stay on the medicines.
  • a T score that is lower than minus-2, and they have had a fracture of one of the vertebrae in the past, stay on the medicines.
  • a T score that is higher than minus-2 and no past fractures, stop the bisphosphonates and check their bone density test in six to 12 months.

This is general advice, rather than a specific recommendation for you. There may be aspects of your personal medical history that I don’t know. You should talk to your doctor to find out what’s right for you.

While bone mineral density tests can identify people who are at greater risk for fractures, they aren’t the only predictors. Estimates can be made based on other factors that influence how likely you are to fall and break a bone.

A tool developed by the World Health Organization calculates an individual’s real-life risk of suffering an osteoporosis-related fracture in the coming years. FRAX (Fracture Risk Assessment Tool) incorporates bone mineral density scores with other weighted risk factors to arrive at a percent probability that a person will break a hip, vertebra, forearm, or shoulder within 10 years. Risk factors used are age, sex, height, weight, previous fragility fracture as an adult, parental history of hip fracture, current smoking, alcohol use (three or more drinks per day), glucocorticoid use for more than three months, rheumatoid arthritis, and secondary osteoporosis.

The tool was developed for physicians to use to better identify high-risk individuals. If you’ve had a bone density test or if you think you might have an increased risk of osteoporosis, you may want to ask your physician about calculating your FRAX score. The tool is geared for doctors’ use, but you can find it online at www.shef.ac.uk/FRAX. Based in part on the FRAX tool, the National Osteoporosis Foundation recommends that doctors consider drug therapy for men and women ages 50 and over who meet one or more of the following criteria:

  • a history of hip or spinal fractures
  • a T-score of less than –2.5 at the hip or spine
  • a T-score of –1 to –2.5 at the hip or spine together with a 10-year FRAX-estimated risk of at least 20% for a major fracture or 3% for a hip fracture

Watch for these red flags

Still, many people don’t know their bone density measurement or FRAX score. By familiarizing yourself with the factors that increase your chance of falling and breaking a bone, you can get a sense of whether you are at greater risk of sustaining a fracture. If any of the following red flags apply to you, discuss them with your doctor:

  • low levels of physical activity
  • low muscle mass or impaired strength
  • balance problems
  • poor eyesight
  • excessive alcohol use
  • a history of falls
  • the presence of environmental hazards, such as electrical cords or throw rugs in walking paths
  • the use of medications, such as sedatives and blood pressure drugs, that can cause dizziness, lightheadedness, or impaired balance
  • advanced age

(This column is an update of one that ran originally in August 2012.)