Predictors of trough serum gentamicin concentrations in neonates

Neonates admitted to an intensive care nursery frequently receive gentamicin sulfate therapy. This study was undertaken to determine predictors of an elevated (greater than or equal to 2 mg/L) trough serum concentration of gentamicin sulfate (undesirable because of potential toxic effects). A total of 140 infants with birth weight of 496 to 4545 g and gestational age of 23 to 42 weeks who received gentamicin in the first days of life were studied prospectively. The trough serum concentration of gentamicin was not significantly affected by concurrent use of dopamine hydrochloride, indomethacin, furosemide, or umbilical artery catheters. Of 11 infants weighing between 1000 and 1500 g on an 18-hour dosing interval, 55% had trough serum gentamicin concentration of 2 mg/L or more. Use of the recommended 24-hour dosing interval for infants weighing less than 1000 g and an 18-hour schedule for preterm infants weighing more than 1000 g resulted in a significant number of elevated trough serum gentamicin concentrations in the latter. A dosing interval of 24 hours for infants less than 1500 g and 18 hours in infants between 1500 and 3250 g is suggested.