Adherence to monthly and weekly oral bisphosphonates in women with osteoporosis

This primary care database survey evaluated whether osteoporotic women treated with bisphosphonates were more adherent to monthly than to weekly treatment. Both compliance (medication possession ratio [MPR]) and persistence (time to discontinuation) were superior in the monthly ibandronate treatment group. Better control of fracture risk may thus be achieved using monthly treatment regimens. Treatment adherence in osteoporosis is poor. The objective of this study was to evaluate whether monthly bisphosphonate treatment provided superior adherence than weekly treatment. We analysed medical claims from a national prescription database (Thales). All women aged > 45 years receiving a first prescription of monthly ibandronate or weekly bisphosphonates in 2007 were included. Treatment adherence was monitored from initial prescription until January 2008. Compliance was measured by the MPR and persistence by the time from treatment initiation to discontinuation. Multivariate analysis was used to identify variables independently associated with adherence. Twelve-month persistence rates were 47.5% for monthly ibandronate and 30.4% for weekly bisphosphonates. Compliance was significantly higher in the monthly cohort (MPR = 84.5%) than in the weekly cohort (MPR = 79.4%). After adjustment for potential confounding variables, women with monthly regimens were 37% less likely to be non-persistent (HR = 0.63 [0.56-0.72]) and presented a 5% higher mean MPR (84.5% versus 79.3%, p < 0.001) than women with weekly regimens. Other major factors associated with improved adherence were previous densitometry and calcium or vitamin D supplementation (p < 0.01). Adherence to bisphosphonates may be superior for monthly treatment than for weekly treatment and may thus provide improved fracture protection.