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Postmenopausal women who take raloxifene for osteoporosis appear to experience improved spine, hip BMD with addition of PTH, data suggest

Thursday, November 15 2007 | Comments

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What's This? Postmenopausal women with osteoporosis who are being treated with raloxifene experience gains in both spine and hip bone mineral density when parathyroid hormone (1-34PTH) is added to their regimen, according to the results of a new study. Raloxifene also appears to partially maintain these gains in BMD after PTH is discontinued.

Forty-two women aged >=45 years whose last menstrual period was >=5 years earlier were enrolled in the study. All of the women had osteoporosis, with study inclusion criteria being a baseline bone density T-score of <= -2.5 at the spine, total hip, or femoral neck; an osteoporosis-related fracture in addition to a baseline T-score of <= -2.0; or a radiographically confirmed vertebral fracture. The subjects had all been taking raloxifene for >=1 year.

The women were randomized to receive 1-34PTH in addition to raloxifene (60 mg/day) or to continue on raloxifene monotherapy for 12 months. Treatment with 1-34PTH was administered as a 25 mcg subcutaneous injection on a daily basis in the form of the biochemically synthesized 1-34hPTH (the researchers noted that their study began before the approval of human recombinant teriparatide). Every 3 months, samples of fasting morning blood and second morning fasting urine samples were obtained to assess bone formation and bone resorption indices, respectively. Bone density testing of the spine, hip, and forearm was performed at 3, 6, and 12 months. After 12 months, 1-34PTH was discontinued and the patients maintained raloxifene therapy. During the follow-up year, fasting blood and urine samples were obtained every 3 months and bone density was measured at 6-month intervals.

The primary efficacy endpoints were changes in lumbar spine BMD at 12 months and at 24 months within each treatment group.

During treatment with 1-34PTH, biochemical indices rapidly increased, with peak increments ranging from 125% to 584% for the 3 markers (P<.001 vs baseline). At the end of the 12-month treatment period with 1-34PTH, BMD increased a mean of 9.6% in the spine (P<.001), 2.5% in the total hip (P<.005), 3.6% for in femoral trochanter (P<.003), and 1.2% in the femoral neck (NS). However, for the proximal radius, mean BMD significantly decreased 4.3% (P=.003).

For women who received only raloxifene during the 12-month study period, no significant changes were observed at any skeletal site.

Within the 12 months of stopping treatment with 1-34PTH, continued treatment with raloxifene monotherapy resulted in only slight, insignificant BMD losses at all skeletal sites except for the femoral neck, which demonstrated a modest increase (P=.04). At the 24-month study endpoint, BMD at the spine and femoral neck remained significantly higher than at baseline (P<.004 and P<.04, respectively), although BMD at the proximal radius remained significantly lower (P=.02).

"We conclude that patients on raloxifene can expect to have an excellent spine and hip BMD response to 1-34PTH treatment," the study authors wrote.

The study was published online ahead of print Oct. 11 in the journal Osteoporosis International by Cosman F, et al.

This information may concern uses that have not been approved by the FDA.

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