Alendronate, Risedronate Compared in BMD Trial : The 1-year study did not provide data on fractures; clinical relevance of BMD findings questioned.


SEATTLE — Alendronate appears slightly more effective than risedronate at increasing bone mineral density, according to the results of a head-to-head trial presented during the annual meeting of the American Society for Bone and Mineral Research.

However, without fracture data, it's unknown whether such BMD findings will translate into a clinically meaningful difference.

In the double-blinded study involving 1,053 postmenopausal women treated for 1 year, alendronate increased BMD at the hip trochanter by a mean of 3.4%, and risedronate increased trochanter BMD by a mean of 2.1%.

The investigation, known as the Fosamax Actonel Comparison Trial, was conducted with patients from 78 different centers, said Clifford J. Rosen, M.D., who is the director of the Maine Center of Osteoporosis Research and Education, Bangor.

Patients received either 70 mg of alendronate and placebo risedronate once weekly or 35 mg risedronate and placebo alendronate once weekly.

In addition to the hip trochanter, BMD measurements were taken for the total hip, lumbar spine, and femoral neck. BMD was increased a mean 2.2% in the active alendronate group, versus a mean 1.2% in the active risedronate group.

Lumbar spine BMD increased a mean 3.7% with alendronate, versus 2.6% with risedronate. In addition, femoral neck BMD increased a mean 1.6% with alendronate and 0.9% with risedronate, he said.

A greater proportion of patients also either maintained or increased BMD on alendronate. Of the patients on alendronate, 84% at least maintained trochanter BMD and 51% had at least a 3% increase, whereas on risedronate, 68% of patients at least maintained BMD, and 41% had a 3% increase or greater.

In addition, alendronate depressed urine and serum markers of bone turnover to a greater degree than risedronate. There was no difference in the occurrence of adverse events between the two drugs.

Not everyone at the meeting was impressed by the study or its results.

“Marketing,” said Paul D. Miller, M.D., when asked about the trial, which was sponsored by Merck and Co., Inc., the manufacturer of alendronate. It's not clear that the degree of difference reported translates into greater bone strength, he said.

“The problem is that there are no fracture data,” said Dr. Miller, medical director for the Colorado Center for Bone Research, Lakewood. “At these differences, the bone strength may not be very different.”

A larger study over a longer period of time would be needed to acquire fracture data, said Richard Petruschke, Pharm. D., who is a spokesperson for Merck and one of the investigators in the study.

“There is literature to support using these surrogates as being meaningful when taken together,” Dr. Petruschke commented.