Comparing medication adherence in patients receiving bisphosphonates for preventing fragility fractures: a comprehensive systematic review and network meta-analysis

Background: Bisphosphonates are effective in preventing fragility fractures; however, high rates of adherence are needed to preserve clinical benefits. Objective: To investigate persistence and compliance to oral and intravenous bisphosphonates (alendronate, ibandronate, risedronate, and zoledronate). Methods: Searches of 12 databases, unpublished sources, and trial registries were conducted, covering the period from 2000 to April 2021. Screening, data extraction, and risk of bias assessment (Cochrane Collaboration risk-of-bias tool 1.0 & ROBINS-I) were independently undertaken by two study authors. Randomised controlled trials (RCTs) and observational studies that used prescription claim databases or hospital medical records to examine patients’ adherence were included. Network meta-analyses (NMA) embedded within a Bayesian framework were conducted, investigating users’ likelihood in discontinuing bisphosphonate treatment. Where meta-analysis was not possible, data were synthesised using the vote-counting synthesis method. Results: Fifty-nine RCTs and 43 observational studies were identified, resulting in a total population of 2,656,659 participants. Data from 59 RCTs and 24 observational studies were used to populate NMAs. Zoledronate users were the least likely to discontinue their treatment HR = 0.73 (95%CrI: 0.61, 0.88). Higher rates of compliance were observed in those receiving intravenous treatments. The paucity of data and the heterogeneity in the reported medication possession ratio thresholds precluded a NMA of compliance data. Conclusions: Users of intravenously administered bisphosphonates were found to be the most adherent to treatment among bisphosphonates’ users. Patterns of adherence will permit the more precise estimation of clinical and cost-effectiveness of bisphosphonates. Trial registration: PROSPERO 2020 CRD42020177166