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Osteoporos Int. Author manuscript; available in PMC 2010 June 1.
Published in final edited form as: Osteoporos Int. 2009 June ; 20(6): 973–978. doi:10.1007/s00198-008-0772-2.

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RisedronatE and ALendronate Intervention over Three Years (REALITY): Minimal Differences in Fracture Risk Reduction
Jeffrey R Curtis, MD, MPH1,2, Andrew O Westfall, MS3, Hong Cheng, PhD1,4, Kenneth G Saag, MD, MSc1,2,4, and Elizabeth Delzell, ScD1,4 1 Center for Education and Research on Therapeutics (CERTs), University of Alabama at Birmingham, Birmingham, AL
2 3 4

Department of Medicine, University of Alabama at Birmingham, Birmingham, AL Department of Biostatistics, University of Alabama at Birmingham, Birmingham, AL Department of Epidemiology, University of Alabama at Birmingham, Birmingham, AL

Abstract
Background—Bisphosphonates differ in their in vitro potency, avidity for bone, and rapidity of onset in clinical trials. To address potential differences between bisphosphonates in comparative effectiveness, we compared new users of alendronate and risedronate to determine if there were differences in the risk of clinical fractures at 1 year and beyond. Methods—Using claims data from a U.S. health care organization, we identified new, adherent users of weekly alendronate or risedronate and assessed subsequent fractures. We calculated fracture incidence rate differences and ratios between the two agents. Results—There were no significant differences in fracture rates between alendronate users (n=12,956) and risedronate users (n=6,107) at 1 year. Using all available data, the rate of hip fracture was higher among risedronate users compared to alendronate users (absolute rate difference approximately 5 per 1000 person-years). Risedronate users had a higher relative rate [RR] of hip fracture (RR = 1.77, 95% CI 1.15 – 2.74) and similar rates of clinical vertebral and