Alendronate therapy linked to severely suppressed bone turnover

The risk may be heightened among patients who are also being treated with estrogen or glucocorticoids.

Long-term alendronate therapy may be associated with an increased risk of severely suppressed bone turnover, according to researchers at the University of Texas Southwestern Medical Center in Dallas and Henry Ford Hospital in Detroit.

The researchers, led by Clarita Odvina, MD, assistant professor of medicine at the Center for Mineral Metabolism at the University of Texas Southwestern Medical Center, said this finding should raise concern because severely suppressed bone turnover can potentially increase the risk of nonspinal fractures and can delay the healing of such fractures.

Odvina said doctors who are prescribing long-term alendronate to patients with osteoporosis should be aware of this potential complication.

Effects of alendronate

Odvina and her colleagues examined nine patients with osteoporosis who had experienced nonspinal fractures while being treated with alendronate. Of these patients, six had either delayed or absent fracture healing.

The researchers conducted a histomorphometric analysis for each patient, which revealed markedly suppressed bone formation and bone resorption. There was reduced or absent osteoblastic surface in most patients; eight showed a low osteoclastic surface. Eroded osteoclastic surface was decreased in four patients.

“Patients who are on two anti-resorbing agents, such as estrogen and bisphoshonates, may be more likely to develop severely suppressed bone turnover,” Odvina told Orthopedics Today. “The risk also exists among patients on long-term steroids and those who have hypoparathyroidism, mainly because these patients are likely to have low bone turnover to start with.”

Recommendations

Odvina said that when treating patients with osteoporosis, doctors should identify and treat the factors that can affect bone mineral density and the risk of fractures. “An FDA-approved drug — either an antiresorbing or a bone-forming agent — can be added, if appropriate. I am not opposed to using bisphosphonates and I continue to use these agents on patients who will benefit from them.”

Research regarding the risks of alendronate therapy is ongoing. Odvina said studies are needed to determine how long bisphosphonate treatment can safely be given and how the risk of severe suppression of bone turnover can be reduced. She added that some researchers have suggested that bisphosphonate treatment should be stopped after five years, or that intermittent therapy be considered to reduce the risk of developing severely suppressed bone turnover.

For more information:
Odvina C, Zerwekh J, Rao S, et al. Severely suppressed bone turnover: A potential complication of alendronate therapy. J Clin Endocrinol Metab. 2005;3:1294-1301.