Osteoporosis is the bone-thinning disorder that leads to debilitating fractures at multiple sites in the body, especially in postmenopausal women.
Hip and vertebral fractures are the most serious of these. Osteoporosis can be diagnosed with a dual energy x-ray absorptiometry (DEXA) scan that measures bone mineral density.
Before 1995, when alendronate (Fosamax) became the first in a series of effective bisphosphonate medications to counter osteoporosis, estrogen replacement was the only effective way to prevent the progression of osteoporosis in postmenopausal women.
Bisphosphonates initially had to be taken daily with a full glass of water while fasting, and the patient had to remain upright for at least 30 minutes afterward to guard against severe ulcerations of the esophagus. Subsequent advances first allowed the pills to be taken weekly and then just once a month, but keeping to the upright position remained necessary.
Based on the HORIZON study recently published in the New England Journal of Medicine, it now appears that a single, 15-minute, intravenous (IV) infusion of the bisphosphonate zoledronic acid (Reclast) once a year offers the same, or even better, protection against bone fractures as does the more frequent use of the bisphosphonate pills. All participants in the trial also received 1,000 to 1,500 mg of calcium and 400 to 1,200 IU of vitamin D daily.
Compared with the placebo group, the participants given yearly IV infusions of Reclast had a 70 percent reduction in vertebral fractures and a 41 percent lower rate of hip fractures over a three-year period. These results matched or exceeded the results found in earlier trials of bisphosphonate pills.
A single IV infusion can overcome the nuisance factor of taking pills, which leads many people to stop taking the bisphosphonate pills and most of the others to take only about 80 percent of their prescribed pills over the course of a year.
Moreover, some elderly people may even be unable to meet the requirements for taking the bisphosphonate pills at all. On the other hand, some may reject the notion of having an IV infusion of a drug.
One sour note, however: About 1.3 percent of those getting IV zoledronic acid (Reclast) experienced a highly significant 2.5 times greater incidence of serious atrial fibrillation (AF) than did the placebo group. No other serious adverse effects, such as heart attacks or strokes, were reported.
Another report in the same issue of the New England Journal of Medicine, however, analyzed the findings from a different trial, which administered Fosamax pills over a four-year period. That trial also showed a trend toward a greater incidence of AF in those taking Fosamax than in those taking the placebo.
These findings are discouraging because the clear benefits of the bisphosphonate pills had not previously been tainted by any serious adverse effects other than esophageal ulcers. It is not known whether the other bisphosphonate pills increase the risk of AF.
