Ipriflavone not Effective for Osteoporosis

For years, estrogen replacement therapy was the drug of choice for treatment of osteoporosis in postmenopausal women. But the potential risks of HRT sent women searching for alternatives. One option was phytoestrogens — plant-based compounds that bind to estrogen receptors in the body, presumably mimicking the beneficial effects of estrogen without its potential risks. Of the phytoestrogens, the most promising was ipriflavone , a synthetic version of a naturally occurring isoflavone , a type of phytoestrogen.

But a well-designed study published in the March 21, 2001 Journal of the American Medical Association refutes the positive results of previous studies, demonstrating that ipriflavone does not prevent bone loss or reduce the risk of fracture in postmenopausal women. It also cautions that ipriflavone lowers levels of lymphocytes, an effect that could make women more vulnerable to infection.

In the JAMA study, members of the Ipriflavone Multicenter European Fracture Study Group assigned 474 postmenopausal white women with low bone mass aged 45 to 75 to either 200 mg. of ipriflavone taken three times per day or a placebo, for the three-year duration of the trial.

At the end of the trial, the researchers found no significant difference between the treatment groups in regard to bone mineral density measured at the lumbar spine, total hip, and distal radius; in biochemical markers of bone formation or bone resorption; or in the number of vertebral fractures suffered by the women.

The major difference was that women treated with ipriflavone experienced significant drops in their lymphocyte concentration. 13.2% of the ipriflavone-treated women developed lymphocytopenia , a condition defined as a total lymphocyte concentration below 500/µL. Of these women, 52% returned to normal lymphocyte values within one year of discontinuation of the drug; 81% returned to normal within two years.

In reviewing their findings, the researchers cautioned against the use of ipriflavone to treat osteoporosis.

Women throughout much of the world have used ipriflavone since 1969 to treat osteoporosis. More recently it has been sold over-the-counter in the United States as Ostovone.
April 2001 Update