Supplementary Material for: Antimicrobial use monitoring in neonatal population using a Defined Daily Doses method

Introduction: This study aimed to assess the feasibility of using specific Defined Daily Doses for neonates (DDDn) as a standardized metric for monitoring antimicrobial consumption in neonatal populations, thereby enhancing antimicrobial stewardship programs (ASPs). To this end, DDDn values have been established for those antimicrobials that had not previously been defined. Methods: This observational study was conducted in the Neonatology Unit of a tertiary-care teaching hospital. Data on antimicrobial use were prospectively collected from January 2016 to December 2023. Both the DDDn values validated in a previous study and the new DDDn values obtained in the present work were used. Antimicrobial consumption was measured quarterly and expressed as DDDn per 1,000 occupied bed days (OBDs). Additionally, a conversion factor was defined to transform DDD into DDDn. Results: Out of 1,326 prescriptions, 310 met inclusion criteria. The study successfully validated DDDn for 10 antimicrobials, including piperacillin-tazobactam, cefepime, and amoxicillin-clavulanic acid. However, DDDn for certain antimicrobials could not be established due to insufficient prescribing data. The mean global antimicrobial consumption was 5.271 ± 1.435 DDDn per 1,000 OBDs per year. The most commonly used antimicrobials were cefotaxime, amoxicillin-clavulanic acid, and ampicillin. The conversion factor was established for five oral antimicrobials and 17 intravenous ones. Conclusion: DDDn proved to be a feasible tool for monitoring antimicrobial consumption in neonatal populations, offering a standardized metric that could improve ASPs and optimize antibiotic usage. More research is needed to validate DDDn across different antimicrobials and clinical settings.