Alendronate edges risedronate in raising BMD. (Expert Says Study is Flawed).

SAN ANTONIO -- The first head-to-head comparison of two bisphosphonates shows that alendronate is more effective than risedronate in increasing bone mineral density, but at least one observer says the study has design flaws that undermine its results.

In a controlled trial of 549 patients, a once-weekly 70-mg dosage of alendronate (Fosamax) was significantly more effective than a daily 5-mg dosage of risedronate (Actonel) for boosting bone mineral density, Dr. David J. Hosking reported at the annual meeting of the American Society for Bone and Mineral Research.

But some experts consider the study to be seriously flawed because the risedronate regimen involved administering the drug to patients 2 hours after their main meal of the day followed by another 2-hour fast before they consumed any food, medication, or drink besides water. This midday, 4-hour fast regimen is an approved way to administer risedronate in Europe and Canada, but it is nor approved in the United States. The study, which was presented in poster form at the meeting, was conducted at several centers in Europe and one in Brazil.

"The single major determinant of absorption of a bisphosphonate is whether there is food in the patient's gastrointestinal tract, and you can't be sure that it is empty unless the patient has not eaten overnight," Dr. Robert Recker, director of the Osteoporosis Research Center at Creighton University in Omaha, Neb., said in an inteview.

"I don't think that these results make any statement at all regarding the comparable efficacy of these two drugs. It probably only addresses the issue of whether the after-meal regimen works," said Dr. Recker, who has received research funding from Procter & Gamble and Aventis, the companies that ...