Vancomycin dosage in overweight and obese children

PURPOSE: Vancomycin dosages in overweight and obese children were evaluated. METHODS: This retrospective study evaluated data for children who were age 2-17 years, received i.v. vancomycin, and were admitted to a children's hospital from September 1, 2007, through October 31, 2009. Patients were then stratified into two groups: normal-weight patients and overweight or obese patients. The primary objective was to compare the number of vancomycin regimens between groups with a trough concentration of 5-15 μg/mL. Secondary objectives included a comparison of dosage changes and toxicities. Multivariate, conditional logistic regression was performed to assess the relationship between attaining optimal vancomycin concentrations (5-15 μg/mL) and independent variables. RESULTS: Data were collected for 232 courses of vancomycin, representing 187 patients. The mean ± S.D. initial dose for the normal-weight and overweight or obese groups differed significantly (461.3 ± 303.1 mg and 658.4 ± 389.6 mg, respectively; p < 0.01); the milligram-per-kilogram initial vancomycin dose did not. The multivariate analysis revealed that every-eight-hour regimens had increased odds of achieving therapeutic concentrations (p < 0.001), while obese children had decreased odds of achieving therapeutic concentrations (p = 0.037). CONCLUSION: A study of prescribing behavior in one hospital revealed no significant difference in the size of vancomycin doses (in milligrams per kilogram) given to normal-weight children compared with overweight or obese children. Regimens using every-eight-hour dosing were significantly more likely than other regimens to result in a vancomycin trough concentration of 5-15 μg/mL, and regimens for obese children, compared with regimens for nonobese children, were less likely to produce trough concentrations in the same range of 5-15 μg/mL.