GENTAMICIN PHARMACOKINETICS IN PRETERM INFANTS [is less than or equal to] 28 WEEKS GESTATIONAL AGE

Background: The kidney function of preterm infants is immature and their body water volume is large. These characteristics may affect the pharmacokinetics of gentamicin. Objective: To describe gentamicin pharmacokinetics in preterm infants with gestational age of 28 weeks or less. Methods: The indication for gentamicin was to rule out sepsis. Gentamicin was given intravenously for 30 minutes at a dose of 2.5 mg/kg. Trough level was measured prior to the third dose, while peak level was measured 30 minutes after the end of the infusion. Results: Gentamicin levels, peak and trough, were collected from 16 preterm infants. Their gestational was 26 days [+ or -] 2 weeks (mean = SD), birth weight 940 g [+ or -] 230, urine output 3.9 cc/kg/ hour [+ or -] 1.9, gentamicin volume of distribution 0.55 L/kg [+ or -] 0.28, elimination rate constant 0.08/hour 0.04, half-life 10.82 hours [+ or -] 7.34, peak level 6 ug/ml [+ or -] 1.9, trough level 1.4 ug/ml [+ or -] 1.3. Twelve of the 16 infants had BUN and creatinine measurements: BUN 14.7 mg/dl [+ or -] 10.4 and creatinine 0.9 mg/dl [+ or -] 0.3. The elimination rate constant had a significantly negative correlation with creatinine value, r = 0.67, p [is less than] 0.05. Conclusion: Gentamicin volume of distribution in preterm infants with [is less than or equal to] 28 weeks gestational age was nearly double what is reported in 70 kg weight adult (0.25 L/kg). A gentamicin dose of 2.5 mg/kg and a 24 hour interval appears to be appropriate. Elimination rate constant had a negative correlation with creatinine level.