Aging and softer bones seem to be inescapably related—older people have softer bones that are more likely to break with trauma. It’s an issue for both sexes, but especially women, who have a greater risk for broken hips and other fractures. In the last ten years, new drugs have offered the opportunity to greatly reduce the burden of aging-related bone changes. Here is information for women to discuss with their physician.
Background
Many people think of bone as the inert structure on which the body hangs. But bone is an active, living tissue. Living bone is constantly remodeling, like re-paving a highway in tiny sections. Remodeling is important to adapt the bone to changes in muscles, activity, and weight distribution. Another benefit is that remodeling removes tiny bone cracks, weak spots that might expand when the bone is hit with trauma such as a fall. It’s like filling pot holes before they become major street gashes.
The processes in remodeling are resorption (dissolving bone) and formation (putting down new bone). Bone is made up of microscopic units called osteons all joined together. At any time in adults, about 10% of osteons are actively ‘repaving,’ tearing down old structure and laying down new.
All prescription medications to prevent or treat bone softness, osteoporosis, work at the level of remodeling by decreasing bone resorption, although some have additional effects as well.
Medication Types and Examples
- Biphosphonates. Those taken by mouth all have strict rules about how to take them, which reduce the risk of injury to the esophagus (usually to take with water on an empty stomach and stay upright for a certain time). Most can be taken daily or weekly. Alendronate is now generic in the USA (a brand form is Fosamax). Similar drugs are risedronate (Actonel) and Bandronate (Boniva) that can be taken only once a month. Other oral biphosphonates are available in other countries. Zoledronic acid (Reclast; Zometa) is given intravenously and can be given once a year.
- Parathyroid related. Teriparatid (Forteo) is a parathyriod hormone (PTH) fragment. It not only slows resorption, it also increases new bone laydown and absorption of calcium from the stomach. It is given daily by subcutaneous (under the skin) injection.
- Selective Estrogen Receptor Modulators (SERMs). Raloxifine (Evista) decreases both phases of bone remodeling, resorption and formation, but the net is increased bone density.
Risks
- Biphosphonates given intravenously produce a risk of jaw osteonecrosis (bone loss), which may delay healing after dental procedures. It is especially a risk in people with cancer or taking steroids. There are some reports of jaw osteonecrosis in people taking oral biphosphonates as well, but the risk has not been measured.
- Biphosphonates can cause injury to the esophagus.
- PTH related drugs produce an increased risk of osteosarcoma, a bone cancer.
- SERMs produce an increased risk of blood clots (venous thrombosis) and strokes.
- Prolonged treatment may actually weaken bones. A number of cases of unusual bone fractures–low-energy subtrochanteric fractures—have been reported in men and women taking alendronate. It is speculated that suppressing bone turnover prevents the normal repair of microscopic bone cracks, allowing them to expand with minor trauma, weakening the bone.
These are the risks most talked about. Other risks are also present. For example, biphosphonates, the most widely prescribed drug, may lead to abdominal pain and other gastrointestinal problems.
Big Issues
When should preventive treatments be started? How long should biphosphonates be taken? After five years of treatment, women are significantly protected. Many experts say stopping at that time makes sense. For women at high risk, “...continuing [treatment] for 10 years is a reasonable clinical option,” according to the National Osteoporosis Foundation.
What about men? Men at high risk should be offered treatment, but what about those at less than high risk?
Calcium and vitamin D are usually included in the treatment regimen, but there has been recent controversy over the dose of calcium, with one study suggesting twice a day doses increases heart risk.
How bad is the risk of low-energy subtrochanteric and related fractures? Might they just be a risk of low bone density? (Population studies have not been done.)
As of today, there are not crisp, well accepted answers to these questions. More research is vitally needed.
Primary sources
Biphosphonates and low impact femoral fractures” Jennifer Schneider. Geriatrics January 2009, pps 18-23; “Treatment of Osteoporosis: All the Questions We Still Cannot Answer” Michel Laroche. American Journal of Medicine, 2008, v 121, pps 744-747
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