Effect of multiple pharmacy use on medication adherence and drug-drug interactions in older adults with Medicare Part D.
Abstract
OBJECTIVES: To assess the association between multiple pharmacy use and medication adherence and potential drug-drug interactions (DDIs) in older adults.
DESIGN: Cross-sectional propensity score-weighted analysis.
SETTING: 2009 claims data.
PARTICIPANTS: A nationally representative sample of 926,956 Medicare Part D beneficiaries aged 65 and older continuously enrolled in fee-for-service Medicare and Part D that year who filled one or more prescriptions at a community retail or mail order pharmacy.
MEASUREMENTS: Multiple pharmacy use was defined as concurrent (overlapping time periods) or sequential use (non-overlapping time periods) of ≥ 2 pharmacies in the year. Medication adherence was calculated using a proportion of days covered of 0.80 or greater for eight therapeutic categories (beta-blockers, renin angiotensin system antagonists, calcium channel blockers, statins, sulfonylureas, biguanides (metformin), thiazolidinediones, and dipeptidyl peptidase-IV inhibitors). Potential DDIs arising from use of certain drugs across a broad set of classes were defined as the concurrent filling of two interacting drugs.
RESULTS: Overall, 38.1% of the sample used multiple pharmacies. Those using multiple pharmacies (concurrently or sequentially) consistently had higher adjusted odds of nonadherence (ranging from 1.10 to 1.31, P < .001) across all chronic medication classes assessed after controlling for sociodemographic, health status, and access to care factors than single pharmacy…
How strong is the evidence?
Evidence Hub reads this as a cross-sectional, done in people. Its evidence level is 4 of 5 (Low · observational). Observational designs can show an association but not prove cause.
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