A University-based hospital in Bogotá, Colombia, developed and implemented an educational intervention to complement a new structured antibiotic order form. This intervention was performed after assessing the appropriateness of the observed antibiotic prescribing practices using a quasi-experimental study. An application of interrupted time series intervention analysis was conducted in three antibiotic groups (aminoglycosides, cephradine/cephalothin, and ceftazidime/cefotaxime) and their hospital weekly rate of incorrect prescriptions before and after the intervention. A fourth time series was defined on prophylactic antibiotic use in elective surgery. Preintervention models were used in the postintervention series to test for pre-post series level differences. An abrupt constant change was significant in the first, third, and fourth time series indicating a 47, 7.3, and 20% reduction of incorrect prescriptions after the intervention. We conclude that a structured antibiotic order form, coupled with graphic and educational interventions can improve antibiotic use in a university hospital.