Medicare Part D and potentially inappropriate medication use in the elderly.

OBJECTIVES: Inappropriate medication use, which is common in older adults, may be responsive to out-of-pocket costs. We examined the impact of Medicare Part D on inappropriate medication use among Medicare beneficiaries. STUDY
DESIGN: Pre-post with comparison group.
METHODS: Using data from 34,679 elderly beneficiaries in Medicare plans from 2004 to 2007, we used Healthcare Effectiveness Data and Information Set measures of prescribing quality: (1) any use of Drugs to Avoid in the Elderly (DAE), (2) a proportion of total medication use attributable to DAEs, and (3) any Potentially Harmful Drug-Disease Interactions in the Elderly (DDE). Rates of inappropriate use among 3 groups transitioning from no drug coverage or limited coverage ($150 or $350 quarterly caps) to Part D in 2006 were compared with those with constant drug coverage.
RESULTS: DAE use increased slightly among those moving from no coverage to Part D (from 15.72%-17.61%) whereas the comparison group's use decreased (20.97%-18.32%) [relative odds ratio (ROR) = 1.34, 95% confidence interval [CI] 1.22-1.48, P <.0001]. However, the proportion of total drug use attributable to DAEs declined among the no coverage group after Part D (3.01%-1.98%), a significant difference relative to the comparison group (ROR = 0.84, 95% CI 0.72-0.98, P = .03). Rates of DDE were low (1%) both before and after Part D.
CONCLUSIONS: While use of high-risk drugs increased slightly among those gaining Part D drug coverage, high-risk drug use actually declined as a proportion of total drug use, and the prevalence of drug-disease interactions remained stable.