Relationship between vancomycin dosage and serum trough vancomycin concentrations in pediatric patients with cystic fibrosis

Purpose. The association between vancomycin dosage and serum trough vancomycin concentrations in pediatric patients with cystic fibrosis (CF) was examined. Methods. A retrospective chart review was conducted for pediatric patients with CF who received vancomycin between 2006 and 2012 at a children's hospital. Admission-level data, including vancomycin dosage regimens and corresponding serum trough vancomycin concentrations, were collected. Student's t tests, analysis of variance, and Pearson's correlation coefficients were used to test for associations between vancomycin dosage and trough concentrations. Results. Data from 40 hospital admissions (31 patients) were analyzed. Initial vancomycin dosages ranged from 45 to 100 mg/kg/day (mean +/- S.D. 62.9 +/- 14.5 mg/kg/day), and the mean +/- S.D. serum trough vancomycin concentration was 9.7 +/- 5.1 mg/L. Patients received a mean +/- S.D. of 1.5 +/- 1.1 dosage adjustments. Final dosage regimens ranged from 50 to 120 mg/kg/day (mean +/- S.D., 78.8 +/- 16.0 mg/kg/day), and the mean +/- S.D. trough vancomycin concentration was 13.6 +/- 4.4 mg/L. There was no significant correlation between the initial (r = -0.272, p = 0.090) or final (r = 0.024, p = 0.882) vancomycin dosage and corresponding trough vancomycin concentration. A significant correlation was found between dosage and trough vancomycin concentration in patients age 12 years or older for the initial (r = 0.545, p = 0.003) and final (r = 0.425, p = 0.024) dosages, with no significant correlations found in patients younger than 12 years. Conclusion. A study of hospital admissions involving pediatric patients with CF revealed no significant correlation, when all admissions were considered, between the initial or final vancomycin dosage regimen and the corresponding serum trough vancomycin concentration. Both correlations were significant for the subgroup of admissions representing patients who were at least 12 years old.