Piperacillin/tazobactam, imipenem, and meropenem were inappropriately used in 50% of hospitalized patients at Siriraj Hospital. Siriraj Hospital administrators implemented drug use evaluation (DUE) and antibiotic authorization for the aforementioned antibiotics beginning in August 2007. The objective of the study was to determine the effectiveness of antibiotic authorization on patients' clinical outcomes, antibiotic consumption, and antibiotic expenditures.MethodsHospitalized patients who were prescribed piperacillin/tazobactam, imipenem, or meropenem from August to November 2007 were randomly allocated to antibiotic authorization group and no-authorization group. The data on clinical outcomes, antibiotic consumption, and antibiotic expenditures of the patients who received and who did not receive antibiotic authorization were compared.ResultsThe patients who received antibiotic authorization (512 prescriptions) had more favorable clinical outcomes (68.9% vs 60.5%, respectively, P < .01), shorter duration of target antibiotics (7.5 days vs 9.3 days, respectively, P < .01), shorter duration of all antibiotics (12.7 days vs 16.4 days, respectively, P < .01), and lower mortality because of infections (29.4% vs 35.4%, respectively, P = .05) than those who did not receive antibiotic authorization (516 prescriptions). The costs of target antibiotics and all antibiotics in the authorization group were much less than those in the no-authorization group. The annual antibiotic cost savings from DUE and antibiotic authorization requirement could be extrapolated to US $862,704.ConclusionDUE and antibiotic authorization are effective strategies in reducing antibiotic consumption and antibiotic expenditures without compromising the patients' clinical outcomes.