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Fosamax saves bone gain after hormone therapy.

STANFORD, CALIF. -- Women maintained gains in bone density from a year of parathyroid hormone therapy if they followed that with a year on the bisphosphonate alendronate instead of placebo, new data from a randomized study have shown.

The study's 238 postmenopausal women with low bone mineral density received parathyroid hormone 1-84 (PTH 1-84), alendronate (Fosamax), or Fosamax plus PTH 1-84. Lumbar spine bone density improved after 1 year by approximately 5% on PTH 1-84, which was a bigger but not significantly different gain compared with the Fosamax group, according to previously reported interim data.

The PTH 1-84 (an investigational drug with a trade name of Preos) was stopped after 1 year, and 119 women who had been receiving Preos monotherapy were randomized to take either Fosamax or placebo in the study's second year. Patients on either Fosamax monotherapy or the combination therapy in year 1 continued Fosamax alone in the study's second year. Dennis M. Black, Ph.D., said at a meeting on osteoporosis sponsored by the University of California, San Francisco.

The new 2-year data show that women who followed Preos therapy with Fosamax continued gaining lumbar spine bone density, for an overall gain of 12%, compared with baseline (N. Engl. J. Med 2005;353:555-65). Women who took placebo after the year of Preos lost some lumbar spine bone density, for an overall gain of 4%, compared with baseline, said Dr. Black, professor of epidemiology and biostatistics at the university and the lead investigator in the study. He is a speaker for and has received honoraria from Merck & Co., which makes Fosamax. He is also a consultant for the maker of Preos, NPS Pharmaceuticals.

An improvement of about 28% in trabecular spine bone density after the first year grew a bit further to an overall gain of 31%, compared with baseline, in women who got Fosamax in the second year. Trabecular spine density decreased in placebo-treated women, who finished the study with a 14% gain in trabecular spine density, compared with baseline.

"With alendronate you tend to hold the gain that you got with PTH," Dr. Black said. Placebo left patients ahead of where they started, "but not by much, and they were clearly headed downward" in bone density. The findings suggest that PTH therapy should be followed by bone antiresorptive agents of some form, such as Fosamax. "We don't know yet what happens with other antiresorptives" that have not been tested this way, he added.

A separate study by other investigators found that reversing the order of these two therapies also improved bone density, but not as much as one might expect, Dr. Black said.

In this study, 126 postmenopausal women with osteoporosis who had taken 70 mg/week of Fosamax for at least 1 year were randomized to continue on oral Fosamax therapy alone or to add daily or cyclic injections of PTH 1-34 (Forteo) at a dose of 25 mcg/day, which is slightly higher than the marketed dose for Forteo (N. Engl. J. Med. 2005;353:566-75).

After 3 months, the Fosamax-only group had increased lumbar spine density by about 1%, compared with baseline at the start of the 15-month study, and patients in the Forteo groups showed about a 6% gain in lumbar spine density, compared with baseline.

The data support findings from a 2004 study showing that women who stopped Fosamax after 18-36 months of treatment and switched to Forteo for 18 months had about a 4% gain in lumbar spine bone density, compared with density at the start of Forteo therapy.

In patients who have not been previously treated with Fosamax, one would expect to see a 7%-8% gain in lumbar spine density on Forteo therapy, Dr. Black said.

It's unclear whether previous treatment with other bisphosphonates will blunt the effects of PTH therapy in the same manner, but studies are under way.


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Title Annotation:Rheumatology
Author:Boschert, Sherry
Publication:Internal Medicine News
Geographic Code:1U9CA
Date:Sep 15, 2005
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