The World Health Organization (WHO) considers antimicrobial resistance one of the top ten global public health threats, mainly driven by inappropriate antimicrobial prescribing. Stewardship programs aimed at optimizing prescriptions can help control resistance, improve infection cure rates, and reduce hospital costs. In this context, early antibiotic auditing within the first 24 hours of prescription has proven to be an effective tool to promptly evaluate and adjust antimicrobial therapy.

This case report describes the implementation of a “Day-1 antibiotic audit” conducted by the infectious disease team, with support from the Infection Control Service (SCIH) pharmacist, in a philanthropic hospital. The goal was to review the indication, antibiotic selection, and treatment duration.

Each day, the SCIH pharmacist issues a report identifying antibiotics prescribed within the last 24 hours that are still in their first day of administration. This list is shared with infectious disease physicians, who will evaluate the patient through an interconsultation. The audit was implemented in December 2024 as part of the hospital’s pre-existing antimicrobial stewardship initiatives.

During the first six months, 543 antibiotic prescriptions were audited; 28% required interventions such as discontinuation, de-escalation/escalation, or route modification. The remaining prescriptions complied with the institutional empirical antibiotic protocol. Beyond promoting rational antimicrobial use, the Day-1 audit also yielded measurable pharmacoeconomic outcomes. In the program’s first semester, total cost savings amounted to BRL 214,086.65, achieved through therapy adjustments and earlier hospital discharges when intravenous-to-oral conversion or discontinuation was feasible.

The Day-1 antibiotic audit proved to be a viable and effective strategy, contributing to both the financial sustainability of the institution and the optimization of antimicrobial prescribing practices.