Effects of Medicare Part D on drug affordability and use: Are seniors with prior high out-of-pocket drug spending affected more?

Res Social Adm Pharm. 2010 Jun;6(2):90-9. doi: 10.1016/j.sapharm.2010.02.004.


Background: Medicare Part D was expected to have differential impacts on patient drug expenditures and use based on beneficiaries' levels of pre-Part D patient drug spending, but it is unknown whether these projections have borne out.

Objectives: We sought to evaluate whether and how the policy effect of Medicare Part D on drug expenditures and use was modified by levels of pre-Part D drug spending.

Methods: A quasi-experimental, pretest-posttest, nonequivalent control group design was used. Data were obtained from a regional supermarket chain for all prescriptions dispensed between January 1, 2005, and December 31, 2007 (n=1,230,612) to patients aged 60 years and older as of January 1, 2005 (n=51,305) to construct 12-month pre-Part D and post-Part D periods. Annual medication use was measured as the total number of pill days acquired. Annual drug expenditures were measured as total expenditures, patient out-of-pocket expenditures, and the proportion of total expenditures paid out of pocket by the patient.

Results: Part D resulted in significant reductions in out-of-pocket spending (17.6%) and significant increases in drug use (4.0%) for individuals in the highest pre-Part D drug-spending group relative to controls. The reduction in out-of-pocket spending for the highest pre-part D spending group was significantly greater compared with the moderate and lowest pre-Part D spending groups.

Conclusions: Our findings suggest that, as expected, Part D facilitated access to medications for patients who previously experienced the greatest costs without adversely increasing use and costs among those with the lowest prior cost.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Age Factors
  • Aged
  • Aged, 80 and over
  • Case-Control Studies
  • Community Pharmacy Services / economics*
  • Cost Control
  • Drug Costs*
  • Drug Prescriptions / economics
  • Eligibility Determination
  • Female
  • Financing, Personal*
  • Health Care Reform
  • Health Services Accessibility / economics*
  • Health Services Research
  • Humans
  • Income
  • Insurance Coverage / economics*
  • Insurance, Pharmaceutical Services / economics*
  • Male
  • Medicare Part D / economics*
  • Prescription Drugs / economics*
  • Time Factors
  • United States


  • Prescription Drugs