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| |  Study Suggests Cumulative Effect From Antiresorptive Therapy and Teriparatide: Presented at ASBMR By John Otrompke DENVER -- September 17, 2009 -- Postmenopausal women previously treated with risedronate may experience better results when subsequently treated with teriparatide than women who have previously been treated with alendronate, according to a study presented here at the 31st Annual Meeting of the American Society for Bone and Mineral Research (ASBMR). According to a computer model created by researchers, vertebral stiffness increased after 12 months in 88% of the women who received teriparatide, who had previously been treated with antiresorptive medication. However, stiffness increased by a mean of 24.6% in those who had previously received risedronate (with the amount varying more or less by 3.2%), compared with 14.4% in those who had previously received alendronate. “This was an in vivo study using a model based on computer tomography images,” said Philippe K. Zysset, PhD, Institute of Lightweight Design and Structural Biomechanics, Vienna, Austria, at an oral presentation on September 13. “I simulated a mechanical experiment on the computer, trying to crush the bone.” Patient data was gathered from the Clinical Effectiveness of Teriparatide After Alendronate or Risedronate Therapy in Osteoporotic Postmenopausal Women (OPTAMISE) study in which patients with severe osteoporosis received antiresorptives for at least 2 years. In addition to measuring vertebral stiffness, the study also concluded that ultimate load increased. In the risedronate group, ultimate load increased by 27.2%, compared with 15.3% in the alendronate group. The difference in the 2 groups was about 10%. The results of the study were not final, he suggested. “Usually teriparatide is given over 2 years; it is possible the difference in the 2 groups will actually go away. There might be some trends, such as the difference in bone marker P1NP, which will tend to decrease with time. Bone formation is more significant early, perhaps in the first through the fifth month, but not so much at later times,” Dr. Zysset explained. He said that part of the explanation in the difference between the 2 groups may lie in the different mechanisms of action of the drugs. “Bisphosphonates like alendronate and risedronate block or freeze bone remodelling. When you have turnover in the cycle of bone resorption, if you have a net imbalance, step by step, you lose a little bit of bone. On the other hand, teriparatide promotes bone remodelling by increasing the amount of bone in those with severe osteoporosis.” The study was also limited by the absence of a control group, so that the existing study populations could be compared with those with no prior bisphosphonate exposure. Funding for this study was provided by the Alliance for Better Bone Health. [Presentation title: Effects of Teriparatide on Vertebral Body Biomechanics in Postmenopausal Women Treated Previously With Risedronate and Alendronate: A QCT-Based Finite Element Study. Abstract 1102]
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