BACKGROUND Proton pump inhibitor (PPI) antacid drugs have been shown to reduce the risk of gastrointestinal bleeding in patients taking antithrombotic medications and have been recommended for high risk patients since the publication of the 2008 ACCF/ACG/AHA consensus recommendations. We aimed to evaluate the rate of PPI use among outpatients receiving antithrombotic therapy at our tertiary care center. METHODS AND RESULTS We performed a retrospective study of cardiology outpatients between January 1st to February 28th, 2019, at an academic care centre. Among patients receiving antithrombotic therapy, we assessed the rate of documented PPI use. Patients were categorized according to the type of antithrombotic regimen as follows: single antiplatelet therapy (SAPT), dual antiplatelet therapy (DAPT), oral anticoagulation (OAC) therapy only, SAPT + OAC, or DAPT + OAC. Patients were stratified according to age 60 years or greater in a sub-analysis. Intergroup comparisons were performed using the chi-square test. A total of 2,503 unique patients were screened during the period of study, of whom 1,665 patients were documented to be receiving at least one antithrombotic agent. Of these, 548 (32.9%) were documented to be receiving PPI therapy (TABLE). The majority of patients were on antithrombotic monotherapy, with about half of patients (49.7%) receiving SAPT and another 35.1% receiving OAC alone. Only 9.8% of patients were receiving DAPT during the period of study and 5.4% were receiving both OAC and either SAPT or DAPT. The rate of PPI use was highest for the minority of patients receiving DAPT + OAC (100%) and those receiving DAPT (62.0%). Slightly under half of patients (45.0%) receiving SAPT + OAC were co-prescribed a PPI. Overall, a third or fewer (32.9%) patients receiving antithrombotic monotherapy were documented to be receiving a PPI. Age 60 years or more was associated with a roughly 50% increase in the rate of PPI co-prescription in the SAPT subgroup only (29% vs 17%, p CONCLUSION Gastrointestinal prophylaxis may be underutilized in cardiology outpatients. The finding that more patients with SAPT over the age of 60 are receiving PPI is in keeping with the 2008 ACCF/ACG/AHA consensus recommendations, but could also be explained by other factors, including weakened lower oesophageal sphincter function and multimorbidities. Additionally, it is important to identify other risk factors for gastrointestinal bleeding, such as prior history of peptic ulcer disease and concomitant steroid use. Targeted interventions to help clinicians recognize patients at risk of gastrointestinal bleeding could help optimize PPI prescription and avoid unnecessary morbidity.