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Presentation
The impact of the Medicare Part D prescription benefit on drug utilization and expenditures
This paper examines changes in prescription utilization and out-of-pocket (OOP) expenditures attributable to Part D among a sample of beneficiaries. We analyzed pharmacy claims data from 2004 to 2007 for beneficiaries aged 66-79 and a control group aged 60-63. Generalized estimating equations (GEE) were used to model changes in expenditures and utilization among beneficiaries accounting for secular trends unrelated to Part D. The final sample represented 5.1 million beneficiaries and 1.8 million control subjects. We also adjusted for individual characteristics, socio-economic characteristics of subjects' zip code of residence. Average monthly drug utilization among all beneficiaries during the penalty-free enrollment period increased by 1.1% (95% CI 0.5%-1.7%), and OOP expenditures decreased by 8.8% (6.6%-11.0%), as a result of the drug benefit. The Part D benefit was estimated to have increased average drug utilization by 5.9% (5.1%-6.7%) and decreased OOP expenditures by 13.1% (9.6%-16.6%) in steady-state (i.e. after enrollment stabilized).