Risk Factors for Non-Therapeutic Initial Steady-State Vancomycin Trough Concentrations in Children and Adolescents Receiving High Empiric Doses of Intravenous Vancomycin

Background: Achieving vancomycin troughs of 15–20 μg/mL remains challenging in children. Our objective was to identify risk factors associated with non-therapeutic initial vancomycin troughs in children. Methods: We conducted a retrospective cohort study of children who received intravenous vancomycin with at least one initial steady-state trough obtained. Patients who achieved therapeutic troughs (15–20 μg/mL in the 20-mg/kg/dose sub-cohort and 10–15 μg/mL in the 15-mg/kg/dose sub-cohort) were compared with those with subtherapeutic troughs (<15 and <10 μg/mL, respectively) and supratherapeutic troughs (>20 and >15 μg/mL, respectively) separately to determine risk factors associated with non-therapeutic troughs. Results: A total of 153 vancomycin courses in 140 patients met study eligibility criteria. Of 45 patients who received 20 mg/kg/dose of empiric vancomycin, 60, 16, and 24% were subtherapeutic, therapeutic, and supratherapeutic, respectively. Each 10-mL/min/1.73 m² increase in initial creatinine clearance (CrCl) was associated with a 47% increase in the odds of an initial subtherapeutic trough (adjusted odds ratio [aOR] 1.47; 95% CI 0.98–2.22). Of 108 patients who received 15 mg/kg/dose of empiric vancomycin, 62, 19, and 19% were subtherapeutic, therapeutic, and supratherapeutic, respectively. Each 10-mL/min/1.73 m² increase in initial CrCl was associated with an 18% increase in the odds of an initial subtherapeutic trough (aOR 1.18; 95% CI 1.02–1.37). Conclusion: Achieving vancomycin troughs of 15–20 μg/mL for severe Gram-positive infections continues to be challenging in children, even at higher empiric doses of 20 mg/kg/dose IV every 6–8 h. Children with higher initial CrCls are particularly susceptible to subtherapeutic initial steady-state vancomycin troughs.