Implementation and Early Outcomes of an Antimicrobial Stewardship Program in South Korea.

: Antimicrobial stewardship programs (ASPs) are essential for promoting the rational use of antibiotics and combating resistance. In South Korea, implementation has recently accelerated, but real-world data on short-term program performance remain limited. This study evaluated the early outcomes of a newly launched ASP at a tertiary hospital. : This retrospective, single-center study analyzed ASP activity from January to April 2025. Interventions included prospective audit and feedback for restricted antibiotics and recommendations for prolonged antibiotic prescriptions (≥14 days). The primary outcome was the monthly rejection rate of restricted antibiotics. Secondary outcomes included days of therapy (DOT) for restricted antibiotics and the acceptance rate of interventions for prolonged prescriptions. : The monthly rejection rate of restricted antibiotics remained stable between 3.65% and 4.68%. Although the DOT values did not show statistical significance, they demonstrated a moderate inverse correlation with the rejection rate (Pearson's r = -0.868, = 0.132). Among 826 prolonged prescriptions, 513 (62.1%) received ASP intervention. Acceptance of recommendations increased over time, from 67.0% in January to 82.5% in April. Interventions were primarily based on insufficient evidence of infection or inappropriate antibiotic selection. : The newly implemented ASP demonstrated feasibility and early impact in improving antibiotic oversight. Despite the short observation period, the findings suggest a positive influence on prescribing practices. Longer-term studies are needed to evaluate sustained clinical outcomes and broader applicability in diverse healthcare settings.