Two-year efficacy and tolerability of risedronate once a week for the treatment of women with postmenopausal osteoporosis

Objective: The efficacy and tolerability of risedronate once-a-week dosing (35 and 50 mg) were compared with risedronate daily dosing (5 mg) in a 2-year study in women with osteoporosis. Design and methods:This was a randomized, double-blind, active-control study with lumbar spine bone mineral density (BMD) as the primary efficacy endpoint at 1 year. Subjects were women aged 50 years or older, postmenopausal for at least 5 years, and had either a BMD T-score of -2.5 or lower (lumbar spine or total proximal femur) or a T-score lower than -2 and at least one prevalent vertebral fracture. In addition to risedronate treatment, the subjects received 1000 mg daily of elemental calcium supplementation and received vitamin D if the baseline serum 25-hydroxyvitamin D-3 level was low. Results: The results after 1 year of treatment were previously published. Of the 1456 women who were randomized and received study medication, 1127 (77%) completed the 2-year study. Over the 2 years of treatment, the incidence of both new vertebral fractures (2.9, 1.5, and 1.7% for the 5, 35, and 50 mg groups, respectively; Paper 2555 p = 0.298) and osteoporosis-related non-vertebral fractures reported as adverse events (5.0, 4.9, and 4.5% for the 5, 35, and 50 mg groups, respectively; p = 0.918) was similar for all 3 treatment groups. The reduction from baseline at Month 24 in bone turnover markers was similar based on an analysis of variance for the 5 mg daily and the 35 mg once-a-week groups. The mean percentage change in lumbar spine BMD after 24 months was 5.17, 4.74, and 5.47% for the 5, :35, and 50 mg groups, respectively. Both the 35 and 50 mg once-a-week treatment groups met the pre-specified criterion of non-inferiority to the 5 mg daily treatment group. No apparent difference in the pattern or distribution of serious and upper gastrointestinal adverse events was observed. Conclusions: The 2-year data agree with the 1-year results demonstrating that the risedronate once-a-week doses are comparable in efficacy and safety to the 5 mg daily dose. Risedronate 35 mg once a week is considered the optimal dose for women with postmenopausal osteoporosis who want a once-a-week dosing regimen.