Objective: This study aimed to evaluate the use and potential drug interactions of proton-pump inhibitor (PPI) in outpatients.Methods: This study is a retrospective descriptive analysis of prescriptions and medical records from outpatients in Gatot Soebroto Army Hospitalselected by purposive sampling who received PPI with one or more other drugs from July to December 2015. The analysis was conducted on 400prescriptions from 192 patients.Results: Data showed that 100% of the PPI therapy utilized was appropriate for the patients’ condition, 79.00% was appropriate for the indication,79.00% was appropriate for the dosage, 79.00% had an appropriate administration duration, and 83.75% was given the appropriate drug. Thepotential of PPI interactions with other drugs was found in 324 prescriptions (81.00%) from 475 cases. Of all the cases, 42 were considered majorinteractions, 138 were moderate interactions, and 295 cases had minor interactions. There were 14 drugs that could potentially interact with PPI, suchas mycophenolate mofetil, clopidogrel, cilostazol, warfarin, iron, levothyroxine, propranolol, cyclosporine, simvastatin, atorvastatin, cyanocobalamin,sucralfate, theophylline, and antacids.Conclusion: PPI use in outpatients at the Gatot Soebroto Army Hospital was not entirely appropriate and had a large number of potential druginteractions with concurrent drugs.