'Healthy Bones' Shot Could Cut Women's Fracture Risk

Osteoporosis primarily affects women in their postmenopausal years, although it can afflict men as well. As bones thin and become more fragile, they break more easily, causing severe disability and even death.

Bisphosphonates, a class of drugs that includes zoledronic acid, are the most commonly used treatment for osteoporosis. They work by slowing the body's natural reabsorption of bone.

But there has been one enduring problem with bisphosphonates: patients don't take the drugs as they should.

"The big concern has been in patient compliance," Brandt confirmed. "The monthly pills run into problems where women start to forget. It's also a pain to take these drugs. You have to sit upright and there's a risk of acid reflux, esophageal damage."

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Women also have to take the pills with a full glass of water while fasting.

According to background information in the paper, most women appear to be taking less than 80 percent of their prescribed pills by 12 months.

Previous research had shown that one annual injection of zoledronic acid improved bone density for at least one year in postmenopausal women with osteoporosis.

The current study looks at how well annual injections do three years out.

Almost 4,000 postmenopausal women were randomly assigned to receive a single 15-minute infusion of zoledronic acid or a placebo at baseline, and then 12 months and 24 months later. Participants were followed out to the 36-month point.

Treatment with zoledronic acid reduced the risk of vertebral fractures by 70 percent (3.3 percent of women in the treatment arm and 10.9 percent of women in the placebo arm suffered such fractures) over three years, the team reported. It also reduced the risk of hip fracture by 41 percent (1.4 percent of women in the zoledronic acid group vs. 2.5 percent in the placebo arm).

Meanwhile, nonvertebral fractures, clinical fractures and clinical vertebral fractures were reduced by 25 percent, 33 percent and 77 percent, respectively.

Women in the treatment arm also experienced significant improvement in bone mineral density and bone metabolism markers.

There was a slight downside to the injections: women in the zoledronic acid group experienced more incidents of an irregular heart rhythm called atrial fibrillation. Other side effects were similar in both groups, the team said.

More information

There's more on osteoporosis at the National Osteoporosis Foundation.