Background: Omeprazole was replaced by lansoprazole as the only proton pump inhibitor on the Veterans Affairs (VA) formulary in February 1997. We aimed to assess the clinical and fiscal impact of this conversion at two VA hospitals. Methods: We identified lansoprazole intolerant patients using pharmacy databases. We reviewed medical records to obtain data regarding reasons for lansoprazole intolerance. The costs of the formulary change and the savings to the VA were calculated. Results: A total of 3833 patients required long‐term proton pump inhibitor therapy; 2224 (58%) were started on lansoprazole and 1479 (39%) were converted from omeprazole to lansoprazole. The remaining 130 (3.4%) patients were never converted from omeprazole to lansoprazole. Of the 3833 patients, 325 (8.5%) currently receive omeprazole therapy; of these, 195 out of 3703 (5.3%) patients are true lansoprazole failures; 172 of these 195 patients completed the study. Most (87%) of the lansoprazole intolerant patients received prior omeprazole. Discontinuation of lansoprazole was due to poor symptom control in 69% and/or side‐effects (22%) including diarrhoea (10%), abdominal pain (5%), or hives (1%). The 1‐year cost of managing lansoprazole failure in 195 patients was $61 690. However, the savings to the VA during the same time period, which totalled $321 360, more than offset the costs associated with the conversion. Conclusions: Lansoprazole intolerance requiring omeprazole conversion occurred in 5% of veterans on proton pump inhibitor therapy for chronic gastro‐oesophageal reflux disease (GERD) symptoms and in 10% of patients with prior omeprazole success. The VA realized substantial cost savings in association with the formulary change.

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