Aminoglycoside volume of distribution in pediatric patients

Pharmacokinetic parameters of three aminoglycoside antibiotics were studied retrospectively in 218 pediatric patients to determine an apparent volume of distribution (Vd) for this age group and to determine if Vd is significantly different in pediatric patients compared with adults. Data on patients considered for inclusion in the study were obtained from the files of the aminoglycoside monitoring services at Saskatoon University Hospital and Regina General Hospital. Both services use a computer program that calculates pharmacokinetic parameters using the Sawchuk-Zaske method. Children between the ages of 1 and 16 years with normal renal function from whom serum concentration had been obtained were included in the study. Exclusion criteria included abnormal or unstable renal function, cystic fibrosis, and pregnancy. The mean age of the pediatric group was 8.65 +/- 5.37 years. Average values for Vd and half-life were 0.34 L/kg and 2.3 h, respectively. No strong correlation was found between the Vd (L/kg) and age. The patients were subdivided into three age groups: 1-4.9 years, 5-9.9 years, and 10-16 years. Group 1 (1-4.9 years) had a larger Vd than the other groups and the Vd of all three groups were significantly different from the estimated Vd of 0.20 L/kg for adult patients. A "normal" pediatric value for the Vd of aminoglycosides could not be determined; however, the Vd in children is significantly larger than the Vd in adults and dosage regimens should be adjusted accordingly.