Long-shelved drug may stop bone loss
As a weapon against osteoporosis, the drug’s beginnings were inauspicious -- it was shelved for almost 50 years, and its main component is a mineral widely regarded as nonessential. But the compound could become a potent treatment for the bone-thinning disorder affecting millions of Americans.
Called strontium ranelate, the medication is made from the mineral strontium, discovered in lead mines in Europe more than a century ago. Strontium is also found in seawater and soil, in tiny amounts in some foods, and in bones and teeth. Chemically, it’s similar to calcium.
It was these similarities that prompted French scientists to revive studies of the mineral. Doctors had stopped using strontium in the 1950s out of fears that it interfered with the synthesis of vitamin D. Those fears appear to have been unfounded.
The researchers recently produced data suggesting that high doses of strontium ranelate -- composed of strontium and ranelic acid -- can contribute to bone strength.
“We do likely have some exposure to strontium in our dietary intakes,” says Dr. Harry K. Genant, executive director of the Osteoporosis and Arthritis Research Group at UC San Francisco. “But the amounts one would get through natural sources would be minuscule relative to the dose used for osteoporosis.”
In a study published in January in the New England Journal of Medicine, researchers with the French drug company Servier randomly assigned 1,649 post-menopausal women with osteoporosis to receive either strontium ranelate or a placebo for three years. Both groups of women also received calcium and vitamin D supplements.
At the end of the study, women who took strontium ranelate -- which is given as a powder that is mixed with water -- showed an increase in bone density and were far less likely to have vertebral fractures. The women who took the placebo had no increase in bone density.
But Dr. Felicia Cosman, clinical director for the National Osteoporosis Foundation, said the study did not show whether the substance helped protect bones other than the spine from fracture. Reducing hip fractures is considered the most important measure of success for an osteoporosis drug.
“What they found on bone density is not better than many of the drugs on the market today,” she says. “And other drugs have shown a decreased risk of fracture throughout the skeleton.”
Several effective osteoporosis drugs are on the market, but most have at least some side effects. Bisphosphonates, such as Fosamax, can cause stomach discomfort but are generally considered safe. Estrogen, which keeps bones healthy, has been linked to a slight increase in stroke and blood clots and has such side effects as vaginal bleeding, mood disturbances and breast tenderness. Raloxifene is generally free of side effects but can cause deep-vein thrombosis, a blood-clotting disorder. And Forteo, the new injectable drug to help build bone, causes side effects such as nausea and leg cramps. It has also been linked to cancer in mice, and its use is limited to two years.
In its favor, strontium ranelate is easily absorbed, safe and free of the side effects associated with some osteoporosis therapies, says Genant, who was an advisor on the study. The most common side effect was diarrhea, experienced by 6% of patients in the study. The drug may be best suited for people who can’t tolerate, or are concerned about, the side effects of other drugs, he says.
“I believe strontium ranelate will have an important niche,” Genant says. “Given that strontium ranelate has such a benign profile, it’s the kind of drug one might be able to take for many years without concerns.”
Scientists aren’t sure how strontium ranelate works, but it seems to prevent bone loss while helping build bone. Other osteoporosis drugs usually do one or the other. Strontium ranelate probably will be marketed for long-term use, both for the prevention of osteoporosis and for treatment, says Dr. Patricia Chatelain, project director for the drug at Servier.
