Dr. Paul Auerbach is the world's leading outdoor health expert. His blog offers tips on outdoor safety and advice on how to handle wilderness emergencies.See all posts »
Biphosphonates, Osteoporosis, and Bone Fractures
X-ray of a fractured femur boneMy 86 year-old mother, who is generally in good health, slipped and fell recently and suffered a fractured femur. She was unfortunate to have suffered the accident, but had the good fortune to be discovered quickly, treated promptly and well by the paramedics who responded to her, and then to have a swift and skillful operation by an orthopedic surgeon to repair the fracture. Almost miraculously, she was standing upright (with a considerable amount of pain) the next day and had begun the rehabilitation process.
At her age—indeed at any age—a fractured femur is a very significant injury. This past year, I have learned of friends and others who have suffered falls and broken their legs, ankles, or backs, as well as others who suffered “pathological fractures.” The latter group had the bones break from normal daily stresses, without a traumatic incident, because the bones were weak and/or osteoporotic. More than a few of these injuries occurred outdoors, associated with stumbles on the trail or falls.
All of this highlights features of an excellent review article that was published this past year in the New England Journal of Medicine. Authored by Murray Favus, MD, it is entitled “Biphosphonates for Osteoporosis” (New England Journal of Medicine 2010;363:2027-35). Anyone who is contemplating taking or administering this therapy would benefit from reading this article. It is well written and comprehensive.
Osteoporosis generally affects many bones in a single person, and is defined by loss of bone tissue, disruption of the bony architecture, and, ultimately, more fragile bones, which are then more prone to breaking. Unfortunately, it is a “silent” disease—the first symptom recognized might be a broken bone, which is often the result of years of unrecognized bone decay. The most common cause of osteoporosis is estrogen deficiency that occurs in women after they reach menopause. For the sake of definition, low bone mass is termed “osteopenia.”
A simplified explanation is that osteoporosis occurs because bone is resorbed at a rate that exceeds bone tissue production to replace the absorbed bone. Biphosphonate medications have been shown to diminish the number of broken bones (fractures) due to osteoporosis because they inhibit bone resorption. The bisphosphonate drugs that are approved for use in the U.S. are alendronate, ibandronate, risedronate and zoledronate. The precise mechanism whereby these drugs work is to accumulate in the bone in such a way as to suppress the activity of the specialized cells (osteoclasts) that perpetrate bone resorption.
How are these drugs used? Postmenopausal women are advised to have measurements of bone mineral density at either the spine or the hip. If the measurement meets criteria for osteoporosis, then long-term therapy with one of these drugs is begun. It is less clear whether osteopenia per se is an indication for beginning similar drug therapy. Dr. Favus commented that he is inclined to initiate treatment for low bone mass in persons who participate in sports or recreational activities such as cycling, tennis, skiing and running. These persons have a greater risk for falls and broken bones than do far less active persons. To his list, I would add frequent or vigorous hiking/trekking, climbing, kayaking, and so forth. His oral drugs of choice are alendronate or risendronate.
There are other drugs that can be used to combat osteoporosis. All of these, as well as bisphosphonates, should be given under the careful guidance of a physician. The other therapies include parathyroid hormone (requires daily injection), estrogen (possible increased risks of breast cancer and cardiovascular disease), the estrogen-receptor modulator drug raloxifene, and calcitonin (nasal stray with limited beneficial effects in preventing fractures).
Drug administration and effects must be closely monitored to avoid or manage side effects, such as kidney toxicity, allergic reactions, vocal cord irritation, and fever. People who should not take biophosphonates include those with vitamin D depletion, osteomalacia (poorly mineralized bones), low serum calcium, certain esophageal disorders, and noncompliant patients. Administration of bisphosphonate drugs is a long-term proposition, and not for everyone.
Regardless of whether or not a person is a candidate for a bisphosphonate drug, if osteoporosis is a consideration, she or he will benefit from adequate dietary calcium intake (1200 milligrams per day from dietary sources; sometimes requiring supplementation) and augmented vitamin D uptake. Weight-bearing exercise is beneficial for prevention and treatment of osteoporosis, but it obviously must be done with caution in order to avoid accidents and creation of bone fractures.
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