title: First-fill medication discontinuations and nonadherence to antihypertensive therapy: an observational study.
abstract: BACKGROUND
  Medication nonadherence is a barrier to successfully managing hypertension, but little is known about the contribution that immediate discontinuations have on antihypertensive (AHT) nonadherence. The purpose of this study was to determine the proportion of new AHT users who discontinue after a single dispensation, and to examine potential predictors of these discontinuations.
  
  
  METHODS
  This retrospective cohort study utilizing linked administrative data from Saskatchewan, Canada. Subjects were ≥40 years of age and received a new AHT between 1994-2002. The primary end point was the proportion of subjects who discontinued their AHT after the first dispensation (first-fill discontinuation). The proportion of nonadherence attributed to first-fill discontinuations was then calculated. Multivariate regression identified factors associated with first-fill discontinuations.
  
  
  RESULTS
  52,039 subjects were included in the analyses. Mean age was 59.4 (s.d. 12.5) years, and 42% were male. Overall, 25,812/52,039 (50%) subjects were nonadherent at 1 year; first-fill discontinuations accounted for 39.1% (10,081/25,812) of this nonadherence. Approximately 20% (10,081/52,039) of all subjects discontinued all AHT therapy after the first fill. A higher chronic disease score (adjusted odds ratio (OR) 1.09, 95% confidence interval (CI) 1.08-1.11) and antidepressant medication usage during the observation year (adjusted OR 1.17, 95% CI 1.09-1.26) was associated with increased risk for first-fill discontinuations. Older age, starting AHT therapy after 1994, frequent physician visits, or use of a statin, acetylsalicylic acid, warfarin or antihyperglycemic during the observation year was associated with a lower risk for first-fill discontinuations.
  
  
  CONCLUSIONS
  A substantial proportion of nonadherence to AHT medications is due to discontinuations after only a single dispensation.
authors.affiliation: College of Pharmacy & Nutrition, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
authors.forename: Charity D
authors.initials: CD
authors.lastname: Evans
authors.forename: Dean T
authors.initials: DT
authors.lastname: Eurich
authors.forename: Alfred J
authors.initials: AJ
authors.lastname: Remillard
authors.forename: Yvonne M
authors.initials: YM
authors.lastname: Shevchuk
authors.forename: David
authors.initials: D
authors.lastname: Blackburn
mesh_terms: D000367:Age Factors; D000368:Aged; D000928:Antidepressive Agents / Q000627:therapeutic use; D000959:Antihypertensive Agents / Q000627:therapeutic use*; D001241:Aspirin / Q000627:therapeutic use; D002908:Chronic Disease; D003863:Depression / Q000453:epidemiology; D005260:Female; D006801:Humans; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000627:therapeutic use; D006973:Hypertension / Q000188:drug therapy*; D007004:Hypoglycemic Agents / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012525:Saskatchewan / Q000453:epidemiology; D014859:Warfarin / Q000627:therapeutic use; D016903:Drug Monitoring
chemical_list: D000928:Antidepressive Agents; D000959:Antihypertensive Agents; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D007004:Hypoglycemic Agents; D014859:Warfarin; D001241:Aspirin