Drug Curbs Osteoporosis Fractures : Medicine: Relatively inexpensive and widely available, it halved the rate of vertebra breaks in a test group of women with brittle bones.
A relatively inexpensive and widely available drug can halve the rate of vertebral fractures in women with osteoporosis, according to a study that may offer a new treatment option for some of the 24 million Americans who suffer from brittle bones.
The drug, called etidronate, is used to treat Paget’s disease, a bone disorder among middle-aged and elderly people. It is not approved for use against osteoporosis, but the manufacturer intends to apply for federal permission.
“The important message is that here is another therapeutic option that is probably as effective as estrogen and calcitonin and that has a low incidence of side-effects,” said Dr. B. Lawrence Riggs, an osteoporosis specialist at the Mayo Clinic and Foundation.
Estrogen therapy is one of several methods of preventing bone loss in post-menopausal women. But it is less effective against more advanced osteoporosis, has some undesirable side effects and cannot be used by women with a high breast-cancer risk.
Calcitonin, another hormone, is often used by women who cannot take estrogen. But in the United States, it must be given by injection. It is also relatively expensive--about 10 times the annual cost of etidronate, researchers said.
The new study, published today in the New England Journal of Medicine, found that two years of etidronate therapy not only halved the vertebral-fracture rate in post-menopausal women but also increased their spinal bone density by an average of 4% or 5%.
The lessening of the fracture rate was especially striking in women who had the weakest bones when the 429-patient study began. In their case, the vertebral-fracture rate was reduced by two-thirds compared to women not taking the drug.
“The most important thing is the demonstration of a reduced rate of fractures,” said Dr. Nelson B. Watts, the study’s principal author. “It doesn’t matter to a patient whether the bones are more dense or not; what matters to them is whether they have a fracture and hurt.”
The study focused specifically on vertebral fractures, the most common fractures in people with osteoporosis. Watts said the number of non-vertebral fractures, such as hip fractures, in the women he studied was too small to show any significant differences between women on and off the drug.
Others cautioned that the drug needs further study to explore, for example, its long-term effects on bone strength and bone-cell activity. They also called for studies comparing the effectiveness of etidronate to that of other osteoporosis treatments.
“Right now we see it as part of that arsenal (of osteoporosis drugs),” said Sandra C. Raymond, executive director of the National Osteoporosis Foundation. “We can’t answer the question, is it more or less effective than anything else?”
“It’s important to emphasize that this is still viewed as experimental therapy,” said Dr. Steven T. Harris of UC San Francisco, a co-author of the study. “It is intriguing, it’s exciting, but it’s experimental.”
Osteoporosis--which can cause fractures of the spine, hip and wrist--affects about 24 million Americans, most of them elderly women. About 5 million of them suffer from spinal osteoporosis and run the risk of painful vertebral fractures.
Such fractures can cause the bones to compress, resulting in a progressive loss of height or in pain from compression of the spinal nerve. Osteoporosis is estimated to cause 1.5 million fractures in the United States each year.
Etidronate works by interfering with so-called bone remodeling, the process by which bones are constantly broken down and rebuilt. The drug inhibits the metabolic activity of cells responsible for breaking down, or resorbing, bone.
Watts estimated the drug’s cost, if used to treat osteoporosis, at $200 to $300 a year.
The study, conducted at seven academic medical centers nationwide, involved women who had already had from one to four vertebral fractures. Some of the women received etidronate while others did not; they all took calcium, a widely used osteoporosis treatment.
The drug was administered by tablet intermittently over two years.
In the end, the women who took etidronate had a vertebral fracture rate of 29.5 per 1,000 patient years--compared to a rate of 62.9 in the non-drug group. The women with the lowest spinal bone density had a rate of 42.3 fractures compared to 132.7.
The findings expand upon those of a much smaller study published two months ago in the journal. That study, involving fewer but sicker patients, found a similar increase in bone mass, absence of side effects and a reduction in fractures.
“We certainly can’t claim that this cures osteoporosis,” said Watts, associate professor at Emory University School of Medicine. “There may be people with such severe disease that we can’t restore them to health. But this certainly improves their lot.”
Etidronate has been available in the United States since 1978 for treatment of Paget’s disease and a bone disorder in cancer patients. It is sold under the brand name Didronel by its manufacturer, Norwich Eaton Pharmaceuticals Inc.
Norwich Eaton helped fund the new study.
Susan Dietrich, a company spokeswoman, said this week that the firm intends to apply soon to the U.S. Food and Drug Administration to make osteoporosis treatment an “approved use” for etidronate. One researcher estimated that an FDA decision could take at least six months.
In the meantime, the law does not prevent physicians from prescribing the drug for so-called “off-label” uses such as treating osteoporosis. But physicians may be leery of risking liability for any unintended consequences of prescribing it for an unapproved use.
