Background: Long-term compliance with pharmacologic treatments for many asymptomatic conditions may be suboptimal, but little is known about compliance with medications used for osteoporosis. This study was undertaken to assess the level and determinants of compliance with drugs prescribed for osteoporosis.
Methods: This retrospective cohort study used pharmacy claims data from US Medicare and filled prescriptions from a state pharmaceutical benefits program. We included persons 65 years or older who initiated use of a medication for osteoporosis (alendronate sodium, calcitonin, hormone therapy, raloxifene hydrochloride, or risedronate) from January 1, 1996, through December 31, 2002. The outcome of interest was suboptimal medication compliance, defined as equal to or less than 66% of days with medication during a 60-day period.
Results: One year after initiating treatment for osteoporosis, 45.2% of the 40,002 patients were not continuing to fill prescriptions. Five years after initiation, 52.1% of patients were not continuing to fill prescriptions for an osteoporosis medication. Several characteristics independently predicted compliance: female sex, younger age, fewer comorbid conditions, using fewer nonosteoporosis medications, bone mineral density testing before and after initiating a medication, a fracture before and after initiating a medication, and nursing home residence during the 12 months before initiating a medication. However, models adjusted for the significant patient variables explained only 6% of the variation in compliance.
Conclusions: Most patients who initiate a medication for osteoporosis do not continue to take it as prescribed. Although several patient characteristics significantly correlated with compliance, adjusted models explained little of the variation.