The Effect of Transitioning to Medicare Part D Drug Coverage in Seniors Dually Eligible for Medicare and Medicaid

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Abstract
OBJECTIVES: To evaluate medication use, out‐of‐pocket spending, and medication switching during the transition period for patients dually eligible for Medicaid and Medicare (dual eligibles). DESIGN: Time‐trend analysis, using segmented linear regression. SETTING: Patient‐level pharmacy dispensing data from January 2005 to December 2006 from a large pharmacy chain with stores in 34 states. PARTICIPANTS: Dual eligibles aged 65 and older. MEASUREMENTS: Changes in utilization, patient copayments, and medication switching were analyzed using interrupted time trend analyses. Utilization and spending were evaluated for five study drugs: clopidogrel, proton pump inhibitors (PPIs), warfarin, and statins (essential drugs covered by Part D plans) and benzodiazepines (not covered through Part D but potentially covered through Medicaid). RESULTS: Drug use for 13,032 dual eligibles was evaluated. There was no significant effect of the transition to Medicare Part D on use of all study drugs, including the uncovered benzodiazepines. Cumulative reductions were seen in copayments for all covered drugs after implementation of Part D, ranging from 25% annually for PPIs to 53% for warfarin, but there was a larger increase in copayments, 91% annually, for benzodiazepines after the transition. The rate of switching medications was 3.0 times as great for the PPIs after implementation of Part D than before implementation, but there was no significant change in the other study drug classes. CONCLUSION: These findings in a single, large pharmacy chain indicate that the transition plan for dual eligibles led to less medication discontinuation and switching than many had expected. The substantially greater cost sharing for benzodiazepines highlights the importance of implementing a thoughtful transition plan when executing such a national policy.