The Impact of Medicare Part D on Medication Treatment of Hypertension

Objective To evaluate Medicare Part D's impact on use of antihypertensive medications among seniors with hypertension. Data Sources Medicare-Advantage plan pharmacy data from January 1, 2004 to December 12, 2007 from three groups who before enrolling in Part D had no or limited drug benefits, and a comparison group with stable employer-based coverage. Study Design Pre-post intervention with a comparison group design was used to study likelihood of use, daily counts, and substitutions between angiotensin-converting enzyme inhibitors and angiotensin-II receptor blockers (ARBs). Principal Findings Antihypertensive use increased most among those without prior drug coverage: likelihood of use increased (odds ratio=1.40, 95 percent confidence interval [CI] 1.25-1.56), and daily counts increased 0.29 (95 percent CI 0.24-0.33). Proportion using ARBs increased from 40 to 46 percent. Conclusions Part D was associated with increased antihypertensive use and use of ARBs over less expensive alternatives.