Inappropriate antimicrobial (ATM) use in hospitals represents a growing public health threat due to the rise of multidrug-resistant microorganisms. Antimicrobial Stewardship Programs (ASP) are essential to optimize prescriptions and mitigate negative impacts. This study evaluated the impact of the ASP implemented in the emergency department of a public hospital in Northern Santa Catarina between June 1 and November 30, 2023, emphasizing changes in prescribing patterns, particularly of broad-spectrum antimicrobials, according to WHO (2014) and ANVISA (2020) guidelines.

Retrospective observational study with a non-probabilistic sample including all cases within the study period. Hospitalized emergency patients who received ATM prescriptions during the 90 days before and after ASP implementation (September 1, 2023) were analyzed. Patients of both sexes, regardless of age or diagnosis, were included. Topical antimicrobials, antiparasitics, and antifungals were excluded. ASP-selected ATM (cefepime, ertapenem, imipenem/cilastatin, meropenem, piperacillin/tazobactam, teicoplanin, and vancomycin) were analyzed separately. Data were obtained from electronic medical records and administrative databases. Variables such as number of hospitalizations, ATM prescriptions, eligible antimicrobials, diagnoses, and clinical outcomes were evaluated. Statistical analysis was performed using Excel with descriptive and comparative tests, adopting a significance level of α = 0.05.

Pearson’s chi-square test was applied to compare pre- and post-ASP periods. Total antimicrobial prescriptions: 739/674 (p = 0.7605); ASP-included antimicrobials: 179/134 (p = 0.0627). Piperacillin/tazobactam prescriptions decreased from 138 to 102 (p = 0.0886) and further to 85 after program adjustments (p = 0.003), showing a statistically significant reduction. Total hospitalizations were 3,139 in the pre-implementation period and 2,908 afterward.

Although not all reductions reached statistical significance, a positive impact of the ASP was observed, particularly among broad-spectrum antimicrobials. Implementation of the ASP contributed to the rational use of antimicrobials and to combating microbial resistance, proving to be an effective and replicable intervention consistent with national and international guidelines.