OBJECTIVE: To analyze the safety, effectiveness and cost savings of rabeprazole at the McGuire Veterans Affairs Medical Center. Similar effectiveness and safety profiles among the proton pump inhibitors (PPI) prompted a dose-per-dose interchange (1:1) of rabeprazole with currently prescribed PPIs (lansoprazole and omeprazole) when rabeprazole was added to the VA National Formulary priced 75%-80% less than its competitors. Rabeprazole was also identified as drug-of-choice for future use in PPI-naïve patients. METHODS: Patients with active rabeprazole prescriptions (N=3885) and those failing therapy (N=249) as of 5/22/02 were selected for analysis (total N=4134). Patients were divided into two subsets: those participating in the PPI therapeutic interchange: N=2088; and PPI-naïve patients prescribed rabeprazole after formulary addition: N=1797. A retrospective database analysis of 14,565 PPI prescriptions from January 1, 2000-May 22, 2002 was conducted to assess PPI prescribing trends, pharmacy acquisition costs, tolerance, effectiveness and dose creep for these individuals. RESULTS: Safety: Patients experience an adverse drug event (ADE): N=65 (1.6%). Effectiveness: Patients failing rabeprazole: N=184 (4.5%). Total number discontinuing rabeprazole for effectiveness or ADE; N=249 (6%). Estimated annual PPI acquisition costs were reduced 50%, avoiding over 1/2 million dollars (US) in pharmacy acquisition costs despite a 32% increase in units dispense. Final cost analysis will include the effect of dose-creep in rabeprazole patients and associated clinic costs. CONCLUSION: Rabeprazole appears safe, effective, and cost-saving as indicated by the low number of patients discontinuing rabeprazole for either clinical failure or intolerance. Cost savings were significant but offset by a predictable and substantial increase in use. *Data available 10-months post interchange; 1-year data will be presented at meeting.