AHRQ study compares efficacy, risks of osteoporosis drugs.

Many medications reduce the risk of bone fractures in people with osteoporosis, but the most commonly used drugs--bisphosphonates--have not been proven more effective than alternatives, according to a new report funded by the Agency for Healthcare Research and Quality (AHRQ.

The AHRQ report compared the effectiveness and risks of six bisphosphonates: Fosamax (alendronate), Didronel (etidronate), Boniva (ibandronate), Aredia (pamidronate), Actonel (risedronate) and Zometa (zoledronic acid). The report also looked at estrogen, calcitonin (a man-made hormone), calcium, vitamin D, testosterone, parathyroid hormone and selective estrogen receptor modulators (SERMs).

Not enough scientific evidence exists to establish whether bisphosphonates are better at preventing fractures than estrogen, calcitonin or raloxifene, according to the report. Some agents, however, such as estrogen and raloxifene (a SERM), can have serious side effects such as strokes, blood clots in the lungs or bleeding in the uterus. One study found tamoxifen also increased the risk of lung blood clots.

The effectiveness of calcium and vitamin D, meanwhile, may vary according to dosing, how often they are taken and whether the patient taking them is at high risk for a fracture. There is limited evidence to compare the supplements with other therapies for preventing fractures.

Risks associated with many osteoporosis treatments are generally moderate or small, the report concluded. Although ulcers in the esophagus were reported in trials of all the bisphosphonates except Zometa, these also occurred in patients not taking these drugs. In rare cases, dramatic jaw bone deterioration can occur in cancer patients taking intravenous bisphosphonates in large doses.

The report also found that many osteoporosis patients stop taking their medications as prescribed. Some stop because they experience no osteoporosis symptoms. Others stop because of medication side effects or because dosing is too frequent. This finding was also true for supplements such as calcium. Patients who take bisphosphonates in weekly formulations, rather than daily, are more likely to follow prescriptions.

Bisphosphonates, the most commonly used medications for osteoporosis, are non-hormonal drugs that bind to bone to protect against tissue breakdown. AHRQ's analysis found that five bisphosphonates, plus calcitonin, parathyroid hormone, estrogen and raloxifene prevent spinal fractures. Evidence also showed that Fosamax, Actonel and Zometa, as well as estrogen and parathyroid hormone, prevent hip and other non-spinal fractures.

Direct comparisons, however, have not shown bisphosphonates to be superior to other therapies in preventing bone fractures. No single bisphosphonate has been proven most effective in that class.

The AHRQ report, 'Comparative Effectiveness of Treatments To Prevent Fractures in Men and Women With Low Bone Density or Osteoporosis," summarized the scientific evidence in 101 published articles. It was authored by the Southern California Evidence-based Practice Center at the RAND Corporation in Santa Monica, CA.