Compliance with drug therapy for postmenopausal osteoporosis

Introduction Patient compliance with pharmacotherapy for osteoporosis is typically poor in clinical practice; less frequent dosing with bisphosphonates may improve compliance. Methods Using data from 49 US health plans, we identified all women aged >= 45 years with osteoporosis who initiated therapy with a bisphosphonate, calcitonin, estrogen, or raloxifene. Compliance was examined alternatively in terms of incidence of adherence failure (medication days <80% of possible) and persistence failure (gap in therapy >= 90 days), and was compared across treatment groups using Kaplan-Meier methods and Cox proportional hazards models. Results The study population included 18,822 women, 48% of whom initiated weekly bisphosphonate therapy. Overall risk of adherence failure was 47% at 3 months, 70% at 1 year, and 84% at 3 years. Risk of persistence failure was 47% at 1 year, and 77% at 3 years. In multivariate analyses, risk of adherence failure was higher for calcitonin (hazard ratio=2.7 vs weekly bisphosphonate therapy, p<0.01), but comparable for all other therapies. Relative risks of persistence failure were generally similar. Conclusions Approximately three-quarters of women who initiate osteoporosis drug therapy are non-adherent with treatment within 12 months, and almost 50% have discontinued such therapy by this time. Compliance with weekly bisphosphonate therapy is generally no better than that with osteoporosis medications requiring more frequent dosing.