Comparison of the Effects of Once-Monthly Versus Once-Daily Risedronate in Postmenopausal Osteoporosis : A Phase II, 6-Month, Multicenter, Randomized, Double-Blind, Active-Controlled, Dose-Ranging Study

Background: Risedronate 5 mg/d is approved by the US Food and Drug Administration for the treatment and prevention of postmenopausal osteoporosis. Once-monthly dosing options might increase treatment compliance and persistence. Objective: The aim of this study was to compare the tolerability and efficacy of 3 once-monthly risedronate dosing regimens with those of risedronate 5 mg/d. Methods: This Phase II, 6-month, randomized, double-blind, active-controlled, dose-ranging study was conducted at 13 clinical research centers and hospitals in Croatia, Poland, Canada, and the United States between April 2004 and June 2005. Postmenopausal women aged 50 to 85 years with a lumbar spine T-score <-2.0 were randomly assigned to 1 of 4 treatment groups: risedronate 100, 150, or 200 mg/mo or 5 mg/d (active control), administered PO for 6 months. Evaluation of tolerability, the primary study objective, was based on adverse-event (AE) profiles and clinical laboratory values. Efficacy evaluation, a secondary objective, was a noninferiority comparison of the changes from baseline in bone mineral density (BMD) and bone turnover markers (BTMs). Results: Of 370 patients randomized (91, 88, 88, and 103 patients in the risedronate 100-, 150-, and 200-mg/mo and 5-mg/d groups, respectively), 57% were >65 years of age and 99% were white; 316 patients (85.4%) completed the study. Completion rates were not significantly different across treatment groups, nor were reasons for discontinuation. Between-group differences in the incidences of treatment-emergent AEs, serious AEs, and upper gastrointestinal (GI) AEs were nonsignificant. Overall, 6 (7%), 14 (16%), 6 (7%), and 9 patients (9%) withdrew because of AEs in the 100-, 150-, and 200-mg/mo and 5 mg/d groups, respectively. GI disorders were the AEs that most frequently led to study withdrawal (5 [5.5%], 7 [8.0%], 4 [4.5%], and 6 [5.8%]). No trends were observed in the nature or frequency of other AEs causing withdrawal. All serious AEs were considered unrelated to treatment, with the exception of erosive esophagitis in 1 patient (1%) who received the 5-mg/d dose. Mean percentage increases in BMD were 2.10%, 2.99%, and 3.38% with risedronate 100, 150, and 200 mg/mo, respectively, versus 3.05% with 5 mg/d. At the 2 higher monthly doses, the changes from baseline in BMD were not significantly different from those in the 5-mg/d group. Mean BTM values were decreased significantly from baseline in all 4 treatment groups, and the changes from baseline at 6 months at the 2 higher monthly doses were not significantly different from those at 5 mg/d. Conclusions: Overall, in this study, the safety profiles of risedronate 100, 150, and 200 mg/mo were not different from that of risedronate 5 mg/d. Changes in efficacy measures in the monthly treatment groups were considered dose related and were not significantly different between the 5-mg/d group and the 150- and 200-mg/mo groups; similarity was greatest with 150 mg/mo.