title: Patterns and predictors of osteoporosis medication discontinuation and switching among Medicare beneficiaries.
abstract: BACKGROUND
  Low adherence to bisphosphonate therapy is associated with increased fracture risk. Factors associated with discontinuation of osteoporosis medications have not been studied in-depth. This study assessed medication discontinuation and switching patterns among Medicare beneficiaries who were new users of bisphosphonates and evaluated factors possibly associated with discontinuation.
  
  
  METHODS
  We identified patients initiating bisphosphonate treatment using a 5% random sample of Medicare beneficiaries with at least 24 months of traditional fee-for-service and part D drug coverage from 2006 through 2009. We classified medication status at the end of follow-up as: continued original bisphosphonate, discontinued without switching or restarting, restarted the same drug after a treatment gap (≥ 90 days), or switched to another anti-osteoporosis medication. We conducted logistic regression analyses to identify baseline characteristics associated with discontinuation and a case-crossover analysis to identify factors that precipitate discontinuation.
  
  
  RESULTS
  Of 21,452 new users followed respectively for 12 months, 44% continued their original therapy, 36% discontinued without switching or restarting, 8% restarted the same drug after a gap greater than 90 days, and 11% switched to another anti-osteoporosis medication. Factors assessed during the 12-month period before initiation were weakly associated with discontinuation. Several Factors measured during follow-up were associated with discontinuation, including more physician visits, hospitalization, having a dual-energy X-ray absorptiometry test, higher Charlson comorbidity index scores, higher out-of-pocket drug payments, and upper gastrointestinal problems. Patterns were similar for 4,738 new users followed for 30 months.
  
  
  CONCLUSIONS
  Among new bisphosphonates users, switching within and across drug classes and extended treatment gaps are common. Robust definitions and time-varying considerations should be considered to characterize medication discontinuation more accurately.
authors.affiliation: Department of Epidemiology, University of Alabama at Birmingham, Birmingham 35294, AL, USA. yunn@uab.edu.
authors.forename: Huifeng
authors.initials: H
authors.lastname: Yun
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Curtis
authors.forename: Lingli
authors.initials: L
authors.lastname: Guo
authors.forename: Meredith
authors.initials: M
authors.lastname: Kilgore
authors.forename: Paul
authors.initials: P
authors.lastname: Muntner
authors.forename: Kenneth
authors.initials: K
authors.lastname: Saag
authors.forename: Robert
authors.initials: R
authors.lastname: Matthews
authors.forename: Michael
authors.initials: M
authors.lastname: Morrisey
authors.forename: Nicole C
authors.initials: NC
authors.lastname: Wright
authors.forename: David J
authors.initials: DJ
authors.lastname: Becker
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Delzell
mesh_terms: D050071:Bone Density Conservation Agents / Q000008:administration & dosage* / Q000009:adverse effects; D004164:Diphosphonates / Q000008:administration & dosage* / Q000009:adverse effects; D004334:Drug Administration Schedule; D057915:Drug Substitution / Q000639:trends*; D017723:Drug Utilization Review / Q000639:trends; D006801:Humans; D016015:Logistic Models; D006278:Medicare; D016017:Odds Ratio; D010024:Osteoporosis / Q000150:complications / Q000188:drug therapy*; D058866:Osteoporotic Fractures / Q000209:etiology / Q000517:prevention & control*; D010818:Practice Patterns, Physicians' / Q000639:trends*; D012189:Retrospective Studies; D012307:Risk Factors; D013997:Time Factors; D016896:Treatment Outcome; D014481:United States
chemical_list: D050071:Bone Density Conservation Agents; D004164:Diphosphonates