Association of a pharmacist-led antimicrobial stewardship intervention with inpatient antimicrobial use in a county-level hospital: A six-year interrupted time-series study

BACKGROUND: Evidence on long-term, hospital-wide antimicrobial stewardship in county-level hospitals remains limited. We evaluated a pharmacist-led bundled program in a county-level tertiary referral hospital. METHODS: We conducted a retrospective interrupted time-series study using monthly hospital-level data from January 2019 through December 2024. The program combined multidisciplinary governance, departmental accountability, tiered antimicrobial authorization, computerized pre-prescription review, and ward-based pharmacist stewardship. The primary outcome was antimicrobial use density (AUD), expressed as defined daily doses per 100 patient-days; prescribing appropriateness was an exploratory process outcome. RESULTS: Annual hospital-wide AUD decreased from 55.93 in 2019 to 31.10 in 2024. Monthly AUD was already decreasing before implementation (-0.90 per month; 95% CI, -1.47 to -0.32). The immediate level change in January 2020 was not significant (-2.59; 95% CI, -6.18 to 1.01; P = .155), whereas the post-intervention trend remained downward (-0.14 per month; 95% CI, -0.21 to -0.07; P < .001). Appropriateness of sampled special-use antimicrobial prescribing increased from 63.00% to 94.58%. CONCLUSIONS: The bundled program was associated with continued reductions in inpatient antimicrobial use and improved exploratory prescribing-appropriateness indicators over 5 post-intervention years. Transferability and economic feasibility require further evaluation.