Comparison of the Effects of Ossein-Hydroxyapatite Complex and Calcium Carbonate on Bone Metabolism in Women with Senile Osteoporosis

Background and Objective: Calcium and vitamin D supplementation is recommended in patients with osteopenia and osteoporosis. One group that could benefit from this treatment is women with senile osteoporosis. Two sources of supplementary calcium are ossein-hydroxyapatite complex (OHC) and calcium carbonate, but, to date, their comparative effects on bone metabolism have not been studied in women with senile osteoporosis. The objective of this study was to compare the effects of OHC and calcium carbonate on bone metabolism in women with senile osteoporosis.

Methods: This was a randomized, open-label, parallel-group, controlled, prospective study to compare the effects of OHC (treatment group) and calcium carbonate (control group) on bone metabolism. Patients were included between 2000 and 2004 and followed up for a maximum of 3 years. The study was carried out at the bone metabolism unit of two university hospitals in Barcelona, Spain. Subjects were women aged >65 years with densitometric osteoporosis of the lumbar spine or femoral neck. The treatment group received open-label OHC (Osteopor®) at a dose of two 830 mg tablets every 12 hours (712 mg elemental calcium per day). The control group received open-label calcium carbonate at a dose of 500 mg of elemental calcium every 12 hours (1000 mg elemental calcium per day). Both groups also received a vitamin D supplement (calcifediol 266 µg) at a dose of one vial orally every 15 days. Biochemical markers of bone remodelling (osteocalcin by electrochemiluminescence, tartrate-resistant acid phosphatase using colorimetry) were measured at baseline and annually for 3 years. Bone mineral density (BMD) at the lumbar spine and femoral neck was also measured.

Results: One hundred and twenty women were included (55 in the OHC group and 65 in the calcium carbonate group), of whom 54 completed 3 years of follow-up. Levels of serum osteocalcin increased to a greater extent in the OHC group compared with the calcium carbonate group (by a mean ± SD of 0.84 ± 3.13 ng/mL at year 2 and 1.86 ±2.22 ng/mL at year 3 in the OHC group compared with a mean ± SD decrease of 0.39 ± 1.39 ng/mL at year 2 and an increase of 0.31 ± 2.51 ng/mL at year 3 in the calcium carbonate group); the differences between treatment groups were statistically significant (p<0.05) at both years. Changes over time in serum osteocalcin level were also statistically significant (p<0.05) in the OHC group, but not in the calcium carbonate group. Changes in mean BMD at the lumbar spine and femoral neck between baseline and year 3 were −1.1% and 2.5% for OHC and −2.3% and 1.2% for calcium carbonate, respectively.

Conclusion: OHC had a greater anabolic effect on bone than calcium carbonate.