title: Switch patterns of osteoporosis medication and its impact on persistence among postmenopausal women in the U.K. General Practice Research Database.
abstract: OBJECTIVE
  This study aims to describe the switch patterns of osteoporosis medication in postmenopausal women and to explore the impact of switching on persistence.
  
  
  METHODS
  This study used a cohort of postmenopausal women who initiated the first treatment with osteoporosis medication between 1995 and 2008. Selected women had switched at least once to a different frequency or type of osteoporosis medication during follow-up. For each study woman, we identified the first therapy (initial osteoporosis medication), second therapy (medication received at first switch), and, where available, third therapy (medication received at second switch), regardless of how many times she switched during follow-up. Persistence was defined as the number of days from the index date to the end of the last prescription within each episode of use. The Kaplan-Meier method was used to calculate persistence rates at 6 months, 1 year, 3 years, and 5 years.
  
  
  RESULTS
  Of 20,638 women who switched osteoporosis treatment at least once in the study period, approximately 67% switched once, 21% switched twice, and 12% switched three times or more. Persistence rates for the second therapy were highest (% [95% CI], 46.6 [46.1-47.1], 35.0 [34.5-35.5], 18.8 [18.3-19.3], and 11.4 [10.9-11.7] at 6 mo, 1 y, 3 y, and 5 y, respectively), whereas persistence rates for the first therapy were lowest (% [95% CI], 34.3 [33.9-34.8], 21.6 [21.2-21.9], 5.90 [5.68-6.13], and 1.57 [1.45-1.69], respectively).
  
  
  CONCLUSIONS
  Among women who switch their initial medication, even though switching to the second medication improves persistence during the initial therapy, persistence on the second and subsequent therapies remains suboptimal.
authors.affiliation: From the 1Boston Collaborative Drug Surveillance Program, Lexington, MA; and 2Amgen Ltd, Cambridge, UK.
authors.forename: Lin
authors.initials: L
authors.lastname: Li
authors.forename: Andrew
authors.initials: A
authors.lastname: Roddam
authors.forename: Samara
authors.initials: S
authors.lastname: Ferguson
authors.forename: Maurille
authors.initials: M
authors.lastname: Feudjo-Tepie
authors.forename: Andrew
authors.initials: A
authors.lastname: Taylor
authors.forename: Susan
authors.initials: S
authors.lastname: Jick
mesh_terms: D000368:Aged; D050071:Bone Density Conservation Agents / Q000008:administration & dosage* / Q000627:therapeutic use*; D016208:Databases, Factual; D004164:Diphosphonates / Q000627:therapeutic use; D005260:Female; D006801:Humans; D008875:Middle Aged; D015663:Osteoporosis, Postmenopausal / Q000188:drug therapy*; D017698:Postmenopause; D006113:United Kingdom; D016903:Drug Monitoring
chemical_list: D050071:Bone Density Conservation Agents; D004164:Diphosphonates