title: Effects of Medicare Part D coverage gap on medication adherence.
abstract: OBJECTIVE
  To evaluate the effects of the Medicare Part D coverage gap on pharmacy use among a national sample of Medicare beneficiaries and on medication adherence among 2 subsamples with heart failure and/or diabetes.
  
  
  METHODS
  Pre-post design, with comparison group and propensity score weighting.
  
  
  METHODS
  We used a 5% random sample of elderly Medicare beneficiaries enrolled in stand-alone Part D plans in 2007. The comparison group had full coverage in the gap, whereas the 2 study groups had either no coverage or generic-only coverage in the gap. Main outcomes included probability of filling a prescription, monthly pharmacy spending and number of prescriptions filled, and adherence measured by medication possession ratios.
  
  
  RESULTS
  Relative to the comparison group, beneficiaries without drug coverage in the gap reduced the number of prescriptions filled per month by 16.0% (95% confidence interval [CI], 15.5%-16.5%); those with generic drug coverage in the gap reduced it by 10.8% (95% CI, 10.3%-11.4%). Most of the reduction was attributable to reduced use of brand-name drugs. Beneficiaries with heart failure reduced adherence to heart failure drugs by 3.6% (95% CI, 2.9%-4.2%) and beneficiaries with diabetes reduced antidiabetic medication adherence by 10.3% (95% CI, 9.4%-11.3%).
  
  
  CONCLUSIONS
  Medicare beneficiaries reduced medication use (mainly brand-name drugs) after entering the coverage gap. This result suggests that while beneficiaries' financial burden would continue because of the coverage gap, the gap would not result in a large reduction in medication adherence for essential drugs for diabetes and heart failure.
authors.affiliation: Department of Health Policy and Management, University of Pittsburgh, 130 De Soto St, Crabtree Hall A664, Pittsburgh, PA 15261, USA. ytzhang@pitt.edu
authors.forename: Yuting
authors.initials: Y
authors.lastname: Zhang
authors.forename: Seo Hyon
authors.initials: SH
authors.lastname: Baik
authors.forename: Judith R
authors.initials: JR
authors.lastname: Lave
mesh_terms: D000368:Aged; D016001:Confidence Intervals; D003920:Diabetes Mellitus / Q000188:drug therapy; D016568:Drugs, Generic; D006333:Heart Failure / Q000188:drug therapy; D006801:Humans; D019458:Insurance Coverage; D017054:Insurance, Medigap; D054524:Medicare Part D; D055118:Medication Adherence; D057216:Propensity Score; D014481:United States
chemical_list: D016568:Drugs, Generic