title: Bisphosphonate prescribing, persistence and cumulative exposure in Ontario, Canada.
abstract: We studied new users of oral bisphosphonates and found that less than half persisted with therapy for 2 years, and interruptions in use were common. During a median observation period of 4.7 years, 10% of patients filled only a single prescription, 37% switched therapies and median cumulative exposure was 2.2 years.
  
  
  BACKGROUND
  We sought to describe bisphosphonate prescribing, persistence and cumulative exposure among seniors in Ontario, Canada.
  
  
  METHODS
  We used Ontario Drug Benefit pharmacy claims to identify residents aged ≥ 66 years who initiated oral bisphosphonate therapy between April 1996 and March 2009. The first date of bisphosphonate dispensing was considered the index date. Persistence with therapy was defined as continuous treatment with no interruption exceeding 60 days. We examined persistence with therapy and the number of extended gaps (>60 days) between prescriptions over time periods ranging from 1 to 9 years. We also identified the proportion of patients filling only a single prescription and switching to a different bisphosphonate, and calculated the median days of exposure irrespective of gaps in therapy.
  
  
  RESULTS
  A total of 451,113 eligible new bisphosphonate users were identified: mean age = 75.6 years (SD = 6.9), 84% female, and median follow-up length = 4.7 years. Persistence with therapy declined from 63% at 1 year to 46% at 2 years and 12% at 9 years. Among those with at least 5 years of follow-up (n = 213,029), 61% had one or more extended gaps in bisphosphonate therapy. Overall, 10% of patients filled only a single prescription, 37% switched to a different bisphosphonate and the median exposure was 2.2 years.
  
  
  CONCLUSIONS
  Less than half of patients persisted with bisphosphonate therapy for 2 years and interruptions in therapy were common, with most patients experiencing two or more >60-day gaps in therapy. Interventions are needed to improve persistence with bisphosphonate therapy and reduce the frequency of gaps in treatment.
authors: Leslie Dan Faculty of Pharmacy, University of Toronto, 144 College Street, Toronto, ON, Canada M5S 3M2.
authors: A M
authors: AM
authors: Burden
authors: J M
authors: JM
authors: Paterson
authors: D H
authors: DH
authors: Solomon
authors: M
authors: M
authors: Mamdani
authors: D N
authors: DN
authors: Juurlink
authors: S M
authors: SM
authors: Cadarette
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