Cost and utilization outcomes of pharmacist-led medication therapy optimization in a Medicare ACO population.

INTRODUCTION: Medication-related problems are a persistent source of avoidable spending among Medicare beneficiaries, presenting an important opportunity to improve the quality of care for seniors and reduce financial burden on the Medicare program. METHODS: We evaluated a pharmacist-led medication therapy optimization (MTO) program implemented in a Medicare accountable care organization population using a regression-adjusted difference-in-differences design with propensity score matching. The analysis included 1003 treated members and 14 031 matched controls contributing 334 531 member-months of claims data (2022-2025). The MTO program combined pharmacogenomic testing, a nine-vector medication-risk algorithm, comprehensive pharmacist review, and structured recommendations to prescribers. RESULTS: MTO participation was associated with a statistically significant reduction in total medical costs (pooled average treatment effect on the treated: -19.4%, -$246 per member per month [PMPM]; P < 0.001). The treatment effect was strongly duration-dependent, growing from -4.7% in the first three months to -31.9% (-$462 PMPM; P < 0.001) beyond nine months of program benefit. All care settings showed significant reductions: inpatient admissions -43.1% (P < 0.001), emergency department visits -41.3% (P < 0.001), and outpatient visits -28.3% (P < 0.001). CONCLUSION: Medication therapy optimization was associated with significant cost savings. Parallel trends validation and a pronounced dose-response relationship support a causal interpretation. Short-duration evaluations are likely to substantially underestimate the full economic value of an MTO program.