OBJECTIVES: Preventable adverse drug events (ADEs) account for significant healthcare costs and patient morbidity and offer an attractive opportunity for healthcare providers to improve patient care and decrease costs. Pharmacist intervention can prevent admissions and readmissions due to ADEs. An innovative pharmacist-run medication review program was implemented in two pharmacies. This study assessed the ADEs prevented and estimated the potential cost savings of prevented ADEs using literature on ADE prevalence and costs. METHODS: Pharmacists conducted medication reviews from November of 2016 to July of 2017 for patients in two pharmacies. Patients covered by Medicare, Medicaid, or other commercial insurance with diabetes, chronic obstructive pulmonary disease, congestive heart failure, prior myocardial infarction, and/or stroke were included. Patients under age 18 were excluded. Retrospective analysis of de-identified medication review quality documentation sheets was conducted and documented ADEs were compiled. ADE treatment costs and estimates of the proportion of potential ADEs requiring treatment were extracted from the literature. We modeled the potential cost savings in prevented ADEs as the product of number of ADEs prevented, proportion of ADEs requiring treatment, and cost of treating an ADE. Sensitivity analysis was performed for the cost of treating an ADE. RESULTS: This study included 436 patients seen as a part of this medication review program. A total of 272 – 385 potential ADEs where identified. Intervention of the pharmacist in these cases resulted in an estimate of $94,832 (sensitivity analysis: $2,261 - $828,921) - $138, 914 (sensitivity analysis: $13,520 - $264,308) in total potential savings and $218 (sensitivity analysis: $5 - $1,901) - $319 (sensitivity analysis: $31 - $606) in potential savings per patient medication review. CONCLUSIONS: This study provides estimates of cost savings associated with pharmacist interventions that likely prevented patients from experiencing ADEs. Pharmacist identified, potentially-prevented ADE interventions resulted in appreciable potential cost savings.