Head-to-head comparison of Forteo and Fosamax

Nov 15 2007

The osteoporosis drug Forteo works better than Fosamax to strengthen bones in arthritis patients with prednisone-induced osteoporosis, according to a new study from a researcher at the University of Alabama at Birmingham (UAB.)

In a head-to-head comparison of the two drugs, Forteo, part of a class of drugs called parathyroid hormones, more than doubled osteoporosis patients' bone density measurements and significantly reduced the risk of new spinal fractures when compared to those taking Fosamax.

Forteo increased lumbar spine density measurements by 7.2 percent compared to 3.4 percent for Fosamax, and it boosted hip density measurements by 3.8 percent compared to 2.4 percent for Fosamax, the UAB researcher said. The study looked at changes in bone density over the course of 18 months.

The findings are published in the Nov. 15 issue of the New England Journal of Medicine.

“Patients and their doctors need more bone-building options,” said Kenneth Saag, M.D., M.Sc., a professor in the UAB Division of Clinical Immunology and Rheumatology and the study's lead author.

“Because having arthritis and being on medication for that disease is important. Reducing your risk of hip fracture or spinal compression is equally important,” Saag said.

“This study significantly improves our understanding of treatment options for secondary osteoporosis, which is osteoporosis caused by taking glucocorticoid drugs like prednisone,” he said.

Glucocorticoids like prednisone are widely used by arthritis patients and others to help reduce inflammation and shrink swollen tissues and joints. But these drugs can cause another problem – an increased risk of bone loss, bone fracture and osteoporosis.

International guidelines currently recommend a class of drugs called bisphosphonates, which includes Fosamax, for patients diagnosed with and at risk for glucocorticoid-induced osteoporosis. Saag said many experts hope Forteo is part of the next wave of medicines that work to build back bone, reduce bone loss and minimize fracture risks in arthritis patients.

For the NEJM study, 428 adults with glucocorticoid-induced osteoporosis were chosen to receive either a once-daily Forteo injection or a once-daily Fosamax pill. Their spine and hip bone density measurements were taken at the start of the trial and at the end using a DEXA scan, a low-level X-ray machine that detects slight changes in bone density.

In addition to taking bone-density measurements, the study authors found the Forteo patients had higher levels of protein and biological markers of bone formation in their urine when compared to the Fosamax group.

The differences between Forteo and Fosamax in terms of serious side effects were not significant, Saag said. He and the study's co-authors conclude that because parathyroid hormone appears to trigger the growth of bone-forming cells called osteoblasts, Forteo may effectively counteract the negative effects of glucocorticoid use in bones. Fosamax works to counteract osteoporosis through a different cell pathway.

Currently Forteo is only approved for use in postmenopausal women with osteoporosis, and in certain cases for men with hormonal-linked osteoporosis. The drug maker Eli Lilly and Company is awaiting federal approval to have Forteo listed among approved medicines in patients with glucocorticoid-induced osteoporosis.