We performed a pharmacokinetic study of gentamicin (GM) in 30 neonates who were given GM by intravenous drip infusion at a dose of 2.5mg/kg over a period of 30 minutes. The results are sum-marized as follows; 1. The neonates were divided into three groups on the basis of their body weight at birth; i. e., <1, 500g, 1, 500g~2, 500g and>2, 500g. In all groups, blood concentrations at 4 hours post-dosing and trough concentrations tended to decrease on day 4 of life and thereafter. Those neonates who were lighter at birth tended to show lower peak concentrations and higher blood concentrations at 4 hours post-dosing and trough blood concentrations. 2. Reviewing the pharmacokinetic parameters obtained, elimination rate constants were lower than in adults and increased with age. Half-life values decreased with age but were longer than those obtained in adults. In newborns, the distribution volume of the drug was larger and clearance values were much lower than in adults. This tendency was more distinct in neonates with lower body weight. 3. A significant correlation was observed between half-life and serum creatinine (r=0.626) and BUN (r=0.530) levels. 4. Half-life decreased with age. There was a significant correlation between half-life and age in the <1, 500g (r=-0.409) and >2, 500g (r=-0.525) groups. 5. Based on the pharmacokinetic parameters obtained, the recommended form of GM administration to neonates is by intravenous drip infusion at a dose of 2.5 mg/kg over a period of 30 minutes, 1~3 times a day, adjusted according to weight and age.
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