Alendronate May Be Superior to Risedronate for Increasing BMD

Peggy Peck

October 04, 2004

Oct. 4, 2004 (Seattle) — In a comparison study between once-weekly doses of alendronate (Fosamax) and risedronate (Actonel), alendronate increased bone mineral density (BMD) at all measured sites more than risedronate, according to results reported here at the 26th annual meeting of the American Society for Bone and Mineral Research (ASBMR).

In the 12-month study, alendronate was associated with a 62% greater increase in BMD at the hip trochanter, which was the primary end point of the study. At 12 months, patients receiving alendronate increased BMD at the hip trochanter by 3.4% vs 2.1% for risedronate( P < .001). At other sites, alendronate posted similar gains: 2.2% vs 1.2 for total hip BMD ( P < .001); 1.6% vs 0.9% at the femoral neck ( P = .005); and 3.7% vs 2.6% at the lumbar spine ( P < .001). Moreover, the differences reached statistical significance at six months.

The lead investigator of the Fosamax Actonel Comparison Trial (FACT), Clifford Rosen, MD, from the Maine Center of Osteoporosis Research and Education and St. Joseph Hospital in Bangor, Maine, said, "This head-to-head trial supports our meta-analysis of two years ago, which suggested the same level of outcomes."

Dr. Rosen added, "The density of the gains for alendronate were certainly greater than for risedronate, but of equal [importance] and perhaps more importantly, there was no increase for gastrointestinal side effects with either agent."

The study was funded by Merck & Co., the manufacturer of alendronate.

In a statement, Nora Zorich, MD, Ph.D., head of drug development for Procter & Gamble Pharmaceuticals in Cincinnati, Ohio, said, "Bone mineral density is important for determining if a patient needs therapy, but when determining which therapy, fracture reduction is the clinically relevant end point. If Merck had intended to fully compare efficacy, they would have run a head-to-head fracture trial." Risedronate is marketed by Procter & Gamble and Aventis. That point was not missed by ASBMR attendees in the poster hall where the FACT results were reported. "Increased bone density and the risk of fracture represent two different issues," said Paraskevi Sapountzi, MD, a fellow in endocrinology at Loyola University School of Medicine in Maywood, Illinois. Dr. Sapountzi was not involved in the study.

"There is no proof at the moment that increased bone density created with the use of bisphosphonates correlates with a reduction in the risk of fractures among people taking the drugs," Dr. Sapountzi told Medscape. "While some clinicians might use the data in the new study to make a decision on treatment regimens, I think more conservative physicians will await more definitive studies.

"Certainly, if I had a patient on risedronate and that patient tolerated the drug well and appeared to be showing increases in bone density, I would not change medication, despite the results of this trial," Dr. Sapountzi said. "Overall, these are both great drugs and I wouldn't trade one for another on the basis of what we now know about their impact on treatment of people with osteoporosis." Dr. Rosen agreed that the study did not look at fracture rates and suggested that it would take a 10,000-patient study to find a difference in that outcome.

FACT recruited more than 1,000 osteoporotic postmenopausal women with low BMD. Of those, 520 women were randomized to alendronate 70 mg once weekly and 533 to risedronate 35 mg once weekly. In both treatment groups, the average age was 64 years and more than 94% of the subjects were white.

Overall, 84.5% of women in the alendronate group gained or maintained BMD at hip trochanter vs 67.8% of women in the risedronate group, and 87.3% of the alendronate-treated women gained or maintained BMD at the lumbar spine vs 75.6% of women in the risedronate group.

ASBMR 26th Annual Meeting: Abstract SA412. Presented Oct. 1, 2004.

Reviewed by Gary D. Vogin, MD

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