title: Ambulatory antibiotic use and prescription drug coverage in older adults.
abstract: BACKGROUND
  Several studies have shown that use of medications to treat chronic conditions is highly sensitive to out-of-pocket price and influenced by changes in insurance coverage. Because antibiotics target infections and are used for a short period, one may expect antibiotic use to be less responsive to price. However, no studies have evaluated how antibiotic use changes with drug coverage. We evaluate changes in ambulatory oral antibiotic use after implementation of the Medicare drug benefit (Part D).
  
  
  METHODS
  We conducted a comparison group analysis 2 years before and after implementation of Part D using insurance claims data from a large Medicare Advantage plan (January 1, 2004, through December 31, 2007). Outcomes included the likelihood of using any oral antibiotics and major antibiotic subclasses among 35 102 older adults and rates of antibiotic use among those with pneumonia and other acute respiratory tract infections.
  
  
  RESULTS
  Overall antibiotic use increased most among those who did not previously have drug coverage (relative odds ratio [OR], 1.58; 95% confidence interval [CI], 1.36-1.85). Use of the broad spectrum antibiotic subclasses of quinolones (OR, 1.70; 95% CI, 1.35-2.15) and macrolides (1.59; 1.26-2.01) increased more than the use of other subclasses, especially for those with prior drug coverage. Rates of ambulatory antibiotic use associated with pneumonia increased (OR, 3.60; 95% CI, 2.35-5.53) more than those associated with other acute respiratory tract infections (2.29; 1.85-2.83).
  
  
  CONCLUSIONS
  Antibiotic use increased among older adults whose drug coverage improved after Part D implementation, with the largest increases for broad spectrum, newer, and more expensive antibiotics. Our study suggests reimbursement may play a role in addressing inappropriate antibiotic use.
authors.affiliation: Department of Health Policy and Management, Graduate School of Public Health, University of Pittsburgh, 130 De Soto St, Crabtree Hall, Room A664, Pittsburgh, PA 15261, USA. ytzhang@pitt.edu
authors.forename: Yuting
authors.initials: Y
authors.lastname: Zhang
authors.forename: Bruce Y
authors.initials: BY
authors.lastname: Lee
authors.forename: Julie M
authors.initials: JM
authors.lastname: Donohue
mesh_terms: D000284:Administration, Oral; D000368:Aged; D000369:Aged, 80 and over; D000553:Ambulatory Care / Q000379:methods / Q000592:standards / Q000706:statistics & numerical data; D000900:Anti-Bacterial Agents / Q000008:administration & dosage* / Q000191:economics*; D015331:Cohort Studies; D016527:Drug Costs; D011307:Drug Prescriptions / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D019458:Insurance Coverage / Q000706:statistics & numerical data* / Q000639:trends; D016015:Logistic Models; D018942:Macrolides / Q000008:administration & dosage / Q000191:economics; D008297:Male; D006278:Medicare; D054524:Medicare Part D / Q000191:economics; D016017:Odds Ratio; D010818:Practice Patterns, Physicians' / Q000191:economics / Q000706:statistics & numerical data; D015363:Quinolones / Q000008:administration & dosage / Q000191:economics; D012107:Research Design; D012141:Respiratory Tract Infections / Q000188:drug therapy / Q000191:economics; D014481:United States
chemical_list: D000900:Anti-Bacterial Agents; D018942:Macrolides; D015363:Quinolones