Assessment of vancomycin dosing and subsequent serum concentrations in pediatric patients.

BACKGROUND: Because of concerns regarding increasing microbial resistance to vancomycin, adult treatment guidelines recommend higher trough concentrations based on the type of infectious process. Although these recommendations are not specific to pediatrics, the principles can be extrapolated. Desired higher trough serum concentrations will require escalated dosages of vancomycin in children.

OBJECTIVE: To evaluate current dosing regimens and subsequent trough serum concentrations of vancomycin in children, compare these to reference recommended dosages and guidelines, and predict a dosing equation to achieve desired serum concentrations.

METHODS: Pharmacokinetic parameters of children in a community teaching hospital who were prescribed vancomycin from January 2005 to May 2010 were evaluated in this retrospective chart review. Vancomycin dosing and subsequent serum concentrations were analyzed. Therapeutic serum concentrations were evaluated and compared to vancomycin prescribing and monitoring guidelines by year.

RESULTS: Four hundred thirty-five trough serum concentrations determined in 295 patients were analyzed. The average dosages, when evaluated by year, were 48 mg/kg/day (2005-2008) and 59 mg/kg/day (2009-2010). Using trough concentration recommendations of 5-15 mg/L, vancomycin regimens provided therapeutic trough concentrations 78% of the time from 2005 to 2008. Using 10-20 mg/L as the trough recommendations in 2009-2010, only 49% of serum concentrations reached a therapeutic level. Based on our predictive equation for children aged 1 month-18 years with normal renal function, a vancomycin dosage of 70 mg/kg/day is required to provide trough serum concentrations of 10 mg/L; a dosage of 85 mg/kg/day is required to provide trough serum concentrations of 15 mg/L.

CONCLUSIONS: Our institution was primarily using vancomycin dosing regimens that were recommended in pediatric references (40-60 mg/kg/day), which resulted in subtherapeutic serum concentrations in our population based on new monitoring recommendations. Considering that the currently desired therapeutic trough concentrations of vancomycin are 10-20 mg/L, the total daily dosage should be increased.