Vancomycin pharmacokinetics in very low birth weight neonates

The pharmacokinetics of vancomycin hydrochloride was studied in 12 very low birth weight infants. The gestational age (mean ± SD) was 25.9 ± 1.3 weeks and body weight was 769.2 ± 151.5 g at the time of initiation of the study. Vancomycin was infused over a period of 60 minutes in a dosage of 14.2 ± 3.2 mg/kg once daily in 10 patients, twice daily in 1 patient and every 36 hours in 1 patient for a mean of 10.5 ± 4.9 days. Serial blood samples were obtained and the concentration time data were fitted to a one-compartment open model using the ADAPT computer program. A significant positive correlation was found between postconceptional age and vancomycin clearance (P < 0.005) and between vancomycin elimination half-life and plasma creatinine (P < 0.01). A negative correlation existed between plasma creatinine and vancomycin clearance (P < 0.005), between postconceptional age and plasma creatinine (P < 0.005) and between vancomycin half-life and postconceptional age (P < 0.01). On the basis of these findings a vancomycin dosage of 15 mg/kg every 24 hours for infants <1000 g should yield concentrations within the accepted therapeutic range. This susceptible population requires frequent monitoring of vancomycin concentrations because of the high degree of interpatient variability and the continuous maturation of renal function.