Anti-fracture Efficacy of Monthly Risedronate Compared with That of Weekly Risedronate in Postmenopausal Korean Women with Osteoporosis: A Nationwide Cohort Study

BACKGROUND: Intermittent dosing regimens for oral risedronate (once-monthly and once-weekly) were developed for patient convenience. While several studies have reported the anti-fracture efficacy of weekly dosing, few have assessed monthly dosing. The lower efficacy of monthly dosing has been previously suggested. The aim of this study was to compare the anti-fracture efficacy of monthly and weekly dosing. METHODS: We obtained information from the Korea National Health Insurance Service database from 2012 to 2017 of Korean women of ≥50 years of age who used weekly or monthly risedronate. We compared the time of occurrence of the first osteoporotic fracture after the first prescription of risedronate. Using a Cox proportional model, we assessed incidence rate ratios (IRRs) with 95% confidence intervals (CIs) for fractures at any site, and the hip, vertebral, and non-vertebral sites between both regimens. Propensity score weighting was used to balance the treatment groups. RESULTS: The study populations were distributed according to dosing frequency (monthly, 27,329; weekly, 47,652). There was no significant difference in the incidence rate of new fractures in any site (IRR, 1.008; 95% CI,0.963–1.055; P=0.737), hip (IRR, 0.999; 95% CI, 0.769–1.298; P=0.996), vertebral (IRR, 0.962; 95% CI, 0.890–1.040; P=0.330), or non-vertebral (1.022; 95% CI, 0.968–1.078; P=0.439) sites between monthly and weekly risedronate. CONCLUSION: The anti-fracture efficacy at any site and the examined individual sites was similar for the monthly and weekly risedronate regimens. Large-scale randomized controlled trials are required for confirmation.