ABSTRACT

Background: Antimicrobial resistance (AMR) is a global threat owing to the overuse and inappropriate use of antibiotics, including the WHOs ‘Reserve’ category of antibiotics. Antimicrobial stewardship strategy of formulary restriction and preauthorization is an important intervention in curbing the developing resistance, however, the effectiveness of such interventions must be periodically assessed.

Objectives: To verify adherence to the formulary restriction and preauthorization process for reserved antibiotics in adult inpatients, assess prescribing practices including posology, and evaluate consumption trends of both reserved and non-reserved antibiotics.

Methods: This prospective, cross-sectional audit was conducted at a tertiary care teaching hospital in India between April and July 2024. A total of 225 consecutive reserved antibiotic prescriptions were reviewed. Appropriateness of indication, dose, route and method of administration were assessed through bedside validation. Culture practices, empirical vs. definitive use, and de-escalation patterns were recorded. Antibiotic consumption was measured in Days of Therapy (DOT) per 1000 patient-days from 2020 to 2024 and analyzed using Mann–Whitney U and Kendall’s Tau tests.

Results: Among the 225 prescriptions, 96.88% were initiated with clinically appropriate indications. However, 22.94% had incorrect selection of predefined indications within the software system. Empirical therapy accounted for 76.45% of prescriptions; cultures were sent in 95.34% of these, with 56.70% yielding growth. Of these, 33.34% were resistant to the empirical agent. Among cases eligible for de-escalation, 74.19% underwent therapy de-escalation, while the remaining 25.81% were not de-escalated despite susceptibility data supporting it, indicating a potential gap in antimicrobial stewardship practices. Dose and administration were appropriate in 89.77% and 100% of cases, respectively. Meropenem was the most used agent (67.11%), predominantly in critical care units (97.77%). Respiratory tract infections were the most common indication (33.33%). DOT for reserved antibiotics decreased over five years (from 80.81 to 65.55), with a significant downward trend (p=0.016), but no significant compensatory rise in non-reserved use (p=0.9).

Conclusion: The study demonstrated a strong compliance to the formulary restriction and preauthorization intervention process and a sustained reduction in reserved antibiotic consumption. Indication selection, dose adjustment, and de-escalation exhibited few gaps requiring continuous prescriber education, real-time audits, and feedback mechanisms to optimize antimicrobial use.