title: Refill adherence and self-reported adverse drug reactions and sub-therapeutic effects: a population-based study.
abstract: OBJECTIVE
  To assess refill adherence to dispensed oral long-term medications among the adult population and to investigate whether the percentages of self-reported adverse drug reactions (ADRs) and sub-therapeutic effects (STEs) differed for medications with adequate refill adherence, oversupply, and undersupply.
  
  
  METHODS
  Survey responses on self-reported ADRs and STEs were linked to the Swedish Prescribed Drug Register in a cross-sectional population-based study. Refill adherence to antihypertensive, lipid-lowering, and oral anti-diabetic medications was measured using the continuous measure of medication acquisition (CMA). The percentages of self-reported ADRs and STEs were compared between medications with adequate refill adherence (CMA 0.8-1.2), oversupply (CMA > 1.2), and undersupply (CMA < 0.8).
  
  
  RESULTS
  The study included 1827 persons, and the refill adherence was measured for 3014 antihypertensive, 839 lipid lowering, and 253 oral anti-diabetic medications. Overall, 65.7% of the medications had adequate refill adherence, 21.9% oversupply, and 12.4% undersupply. The percentages of self-reported ADRs and STEs were respectively 2.6%, 2.7%, and 2.1% (p > 0.5) for ADRs and 1.1%, 1.6%, and 1.5% (p > 0.5) for STEs.
  
  
  CONCLUSIONS
  Adequate refill adherence was found in two thirds of the medication therapies. ADRs and STEs were unexpectedly equally commonly reported for medications with adequate refill adherence, oversupply, and undersupply. These results suggest that a better understanding of patients' refill behaviors and their perceived medication adverse outcomes is needed and should be considered in improving medication management. The impact of individual and healthcare factors that may influence the association between refill adherence and reported medication adverse outcomes should be investigated in future studies.
authors.affiliation: Division of Drug Research, Department of Medical and Health Sciences, Faculty of Health Sciences, Linköping University, County Council of Östergötland, Sweden; Nordic School of Public Health NHV, Gothenburg, Sweden.
authors.forename: Khedidja
authors.initials: K
authors.lastname: Hedna
authors.forename: Staffan
authors.initials: S
authors.lastname: Hägg
authors.forename: Karolina
authors.initials: K
authors.lastname: Andersson Sundell
authors.forename: Max
authors.initials: M
authors.lastname: Petzold
authors.forename: Katja M
authors.initials: KM
authors.lastname: Hakkarainen
mesh_terms: D000293:Adolescent; D000328:Adult; D016907:Adverse Drug Reaction Reporting Systems / Q000706:statistics & numerical data*; D000368:Aged; D000369:Aged, 80 and over; D062313:Databases, Pharmaceutical; D004339:Drug Compounding / Q000706:statistics & numerical data; D017723:Drug Utilization Review; D064420:Drug-Related Side Effects and Adverse Reactions / Q000453:epidemiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D004364:Pharmaceutical Preparations / Q000600:supply & distribution*; D013548:Sweden / Q000453:epidemiology; D055815:Young Adult; D016903:Drug Monitoring
chemical_list: D004364:Pharmaceutical Preparations
keywords: adverse drug reaction; oversupply; pharmacoepidemiology; refill adherence; self-report; therapeutic failure; undersupply