Studies clash on GI-event risk of bisphosphonates: Fosamax, Actonel.(Gynecology)

SAN DIEGO -- Men and women older than 65 who started bisphosphonate therapy with alendronate had about a 1.5-fold greater risk for gastrointestinal events after 4 months, compared with those who started therapy with risedronate, results from a large retrospective study suggest.

In a related study, GI-related medical costs were nearly three times higher in patients who started therapy with alendronate (Fosamax) than in those who started with risedronate (Actonel), Joseph Doyle, a pharmacist, said in a poster session during the annual meeting of the American Association of Clinical Endocrinologists.

But Dr. Anastasia Daifotis told this newspaper that such studies are "extremely misleading" because they are not head-to-head randomized trials. "These are not real head-to-head comparisons," said Dr. Daifotis, who directs the Fosamax clinical trials for Merck, manufacturer of Fosamax.

Dr. Daifotis also said that the findings contradict results of the longest head-to-head randomized, placebo-controlled trial of alendronate and risedronate, which will be published soon.

For the first study, Mr. Doyle and his associates gathered data from a pharmaceutical claims database licensed by Protocare Sciences, a health care consulting service.

They conducted a retrospective analysis of 3,947 men and women aged 65 and older who were given a prescription for bisphosphonate therapy between November 2000 and August 2001.

Patients who received a prescription for risedronate (5 mg/day) or alendronate (5 mg/day, 10 mg/day, 35 mg/wk, or 70 mg/wk) were selected for analysis. Those who were prescribed a bisphosphonate during the prior 6 months were excluded.