Weekly versus monthly drug regimens: 1-year compliance and persistence with bisphosphonate therapy

Objective: To determine compliance and persistence with weekly risedronate and monthly ibandronate therapy. Research design and methods: The IMS longitudinal prescription database was used to evaluate compliance (mean medication possession ratio), persistence (days until a gap 490 days between prescriptions occurred) and cumulative drug availability (ratio of drug supply and days between first fill date and the end of the study) among patients taking weekly risedronate or monthly ibandronate over a 12-month period using three retrospective cohorts: overall sample, new to osteoporosis therapy, and new to osteoporosis therapy after initial market availability. Comparisons were made between drug groups for each measure. Results: Compliance was significantly different for the overall sample (80.15 +/- 18.90% for risedronate vs. 74.68 +/- 22.56% for ibandronate; p<0.0001), and marginally different during the initial post-marketing year (p = 0.091), but not for patients new to therapy (p = 0.693). Persistence was significantly different for the overall sample (250.04 +/- 132.34 days for risedronate vs. 151.54 +/- 137.24 days for ibandronate; p < 0.0001), for patients new to therapy (154.38 +/- 135.29 days for risedronate vs. 133.33 +/- 130.36 days for ibandronate; p<0.0001), and after initial market availability (165.00 +/- 141.58 days for risedronate vs. 133.33 +/- 130.36 days for ibandronate; p<0.0001). Mean cumulative drug availability was significantly different for the overall sample (64.54 +/- 29.86% for risedronate vs. 43.38 +/- 32.96% for ibandronate; p<0.0001), for patients new to therapy (40.34 +/- 31.84% for risedronate vs. 36.05 +/- 31.09% for ibandronate; p<0.0001), and after initial market availability (43.17 +/- 33.34% for risedronate vs. 36.05 +/- 31.09% for ibandronate; p<0.0001). Conclusions: Patient compliance, persistence and cumulative drug availability were similar for monthly ibandronate and weekly risedronate dosing. Interpretations from this study are limited by assumptions of persistence based on initial drug dosing and selected refill gap length measured. Furthermore, comparisons with earlier studies are difficult, due to differences in definitions of compliance and persistence. Further studies are needed to explore factors affecting patterns of medication use, particularly the effects of patient preference, acceptance, and patient education on compliance and persistence.