Incidence of gastrointestinal events among bisphosphonate patients in an observational setting

Objective: To compare the incidence of gastrointestinal (GI) events among patients initiating alendronate or risedronate therapy. Study Design: Retrospective observational study of an administrative claims database. Methods: Patients aged 65 years and older who received a new prescription for risedronate (n = 865) or alendronate (n = 5255) between November 1, 2000, and May 31, 2002, were selected for analysis. Preexisting GI conditions and medication use for the 2 treatment groups in the 6 months before initiation of bisphosphonates were also determined. A Mantel-Haenszel relative risk estimate was used to compare the incidence of GI events within the first 4 months of treatment. Results: In both the alendronate and risedronate treatment groups, the mean age was approximately 76 years and 93% were female. Treatment groups had a similar overall health status at baseline with the exception that proportionally more individuals who initiated risedronate had preexisting GI conditions compared with alendronate users (13.8% vs 11%, odds ratio = 0.77, P = .02). In the first 4 months following initiation of treatment, 8.2% of alendronate patients and 5.5% of risedronate patients had a documented GI-related event. Adjusting for age, sex, preexisting GI conditions, and number of concomitant medications in the pretreatment period, the alendronate patients exhibited a 44% higher risk of GI events compared with risedronate patients (relative risk = 1.44; 95% confidence interval, 1.03-2.00; P= .03). Conclusion: This analysis of administrative claims from a large managed care database supports a difference between alendronate and risedronate with respect to GI tolerability in the first 4 months of therapy.