Monthly dosing with risedronate 50 mg on three consecutive days a month compared with daily dosing with risedronate 5...

Risedronate 5 mg daily significantly reduces the incidence of vertebral and non-vertebral osteoporotic fractures in postmenopausal women. We compared the efficacy and tolerability of risedronate 50 mg administered on 3 consecutive days per month, with and without a loading dose, with those of risedronate 5 mg daily in a randomized, double-blind study.

Subjects were postmenopausal women 65-80 years old with low bone mineral density (BMD) (T-score < or = -2). Subjects received risedronate 5 mg daily for 6 months (n = 48), risedronate 150 mg (50-mg doses on 3 consecutive days) monthly for 6 months (n = 50), or a loading dose of risedronate 15 mg daily for 1 month followed by 150 mg (50-mg doses on 3 consecutive days) monthly for 5 months (n = 52).

Within 1 week, statistically significant reductions in urine N-telopeptide, the primary efficacy measure, were observed in all three groups. After 6 months, the least squares (LS) mean differences (95% confidence intervals [CI]) from the change in the 5 mg daily group (-39.88) were -3.54% (-15.71; 8.64) for the 150 mg monthly and -2.02% (-14.13;10.10) for the loading dose + 150 mg monthly groups. Mean percent changes in serum alpha-C-telopeptide, bone-specific alkaline phosphatase, and BMD, secondary efficacy measures, after 6 months were also similar for the three groups. The LS mean differences (95% CI) from the mean percent change in BMD in the 5 mg daily group (3.22%) were 0.20 (-1.15; 1.55) for the 150 mg monthly and -0.58 (-1.93; 0.76) for the loading dose + 150 mg monthly groups. The safety profile of the monthly regimens was similar to that of the 5 mg daily regimen and consistent with product labeling.

A monthly regimen of risedronate 50 mg on 3 consecutive days per month was similar to risedronate 5 mg daily with respect to its effect in suppressing bone turnover and increasing BMD and its safety profile in women with postmenopausal osteoporosis. This study was not powered to be a confirmatory trial for non-inferiority; therefore, additional study is needed.