Alendronate adherence and its impact on hip-fracture risk in patients with established osteoporosis in Taiwan.

A pharmacoepidemiology study was conducted using the health insurance database in Taiwan to assess compliance with osteoporosis drug regimens and the impact of compliance on the risk for secondary fractures. Patients >50 years of age with vertebral/hip fracture who had been started on alendronate therapy for the first time only after the fracture were included. Compliance was measured using the medication possession ratio (MPR) and was included as a time-dependent covariate in the Cox model to compare the difference between compliant (MPR ≥ 80%) and noncompliant patients (MPR <80%) with respect to risk for subsequent hip fractures. Only 38% of the study population remained compliant during the first year of treatment. Over the 4-year follow-up period, the risk of hip fracture among the compliant patients was 70% lower than that among the noncompliant ones (adjusted hazard ratio (HR) 0.30). Among patients with osteoporosis in Taiwan who had experienced a fracture and had started alendronate therapy, compliance with the dosage regimen was suboptimal. It was also found that compliance significantly reduced the risk of secondary hip fracture up to 4 years.