title: Lowering copayments: impact of simvastatin patent expiration on patient adherence.
abstract: OBJECTIVE
  To assess the impact of a decrease in statin copayments on medication adherence and demand for statins.
  
  
  METHODS
  Quasi-experimental, pre/post design.
  
  
  METHODS
  Patients in more than 700 health plans from June 2005 to May 2007 were evaluated. The intervention group (n = 13,319) and matched control group (n = 26,569) included patients who had at least 1 branded simvastatin or non-simvastatin statin purchase, respectively, before the simvastatin patent expired in June 2006. Intervention and control patients had to have purchased at least 1 generic simvastatin and non-simvastatin statin, respectively, after patent expiration. Intervention patients were matched to control patients up to 1:2 on incident statin use (yes/no) and pre-patent expiration copay (+/- $2). Adherence was calculated with the medication possession ratio (MPR). Adjusted and unadjusted changes in MPR were compared between groups. Elasticity of demand for statins was estimated.
  
  
  RESULTS
  A small but statistically significant difference was observed between groups in the change in MPR (intervention = 0.52% adjusted mean increase, control = 2.02% adjusted mean decrease; adjusted P <.01). A marginally higher percentage of intervention patients (10.5%) compared with control patients (10.0%) increased their MPR from <80% in the preperiod to > or = 80% in the postperiod (adjusted P <.01). Elasticity of demand for statins was estimated at 0.02 and -0.02 for the copayment reduction categories of $0 to $5 and >$15, respectively.
  
  
  CONCLUSIONS
  Decreasing statin copayments was associated with adherence increases. However, the overall increase in medication adherence was modest and its clinical significance uncertain.
authors.affiliation: Office of Evidence-Based Pharmacy Benefit Design, Express Scripts Inc, St Louis, MO 63121, USA. rsedjo@express-scripts.com
authors.forename: Rebecca L
authors.initials: RL
authors.lastname: Sedjo
authors.forename: Emily R
authors.initials: ER
authors.lastname: Cox
mesh_terms: D000328:Adult; D000924:Anticholesteremic Agents / Q000191:economics / Q000627:therapeutic use; D015331:Cohort Studies; D017047:Cost Sharing / Q000706:statistics & numerical data*; D004345:Drug Industry / Q000191:economics / Q000331:legislation & jurisprudence; D016568:Drugs, Generic / Q000191:economics*; D005252:Fees, Pharmaceutical; D005260:Female; D006264:Health Benefit Plans, Employee / Q000191:economics; D006801:Humans; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000191:economics / Q000627:therapeutic use; D007356:Insurance, Pharmaceutical Services / Q000191:economics; D008297:Male; D008329:Managed Care Programs / Q000191:economics*; D008875:Middle Aged; D010330:Patents as Topic; D019821:Simvastatin / Q000191:economics* / Q000627:therapeutic use*; D014481:United States; D055815:Young Adult; D016903:Drug Monitoring
chemical_list: D000924:Anticholesteremic Agents; D016568:Drugs, Generic; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D019821:Simvastatin