GENTAMICIN DOSAGE IN CHILDREN - RANDOMIZED PROSPECTIVE COMPARISON OF BODY-WEIGHT AND BODY-SURFACE AREA AS DOSE DETERMINANTS

Body surface area and body weight were evaluated as gentamicin dose determinants in a randomized prospective study of 35 children with normal renal function. Patients were randomly assigned to receive i.v. gentamicin doses of 37.5 mg/m2 (Group I) or 1.25 mg/kg (Group II) administered every 6 h and were studied after their 1st dose on days 1, 3 and 6 of therapy. When the variability in peak concentrations for the 2 dosage regimens was compared, there was no statistically significant difference (P = 0.45) between the 2 groups. The gentamicin volume of distribution for all patients correlated only moderately with body weight (r = 0.82) and body surface area (r = 0.79). The mean volume of distribution on day 1 was 0.295 .+-. 0.115 l/kg when expressed as a function of body weight and 7.26 .+-. 2.62 l/m2 when expressed as a function of body surface area, and did not change significantly with multiple dosing. The variability in serum concentrations is apparently not significantly reduced when pediatric doses are calculated from body surface area instead of body weight, supporting the need for individualization of doses based on measured serum concentrations.