Pharmacokinetics of netilmicin in premature infants

The pharmacokinetics of netilmicin were studied in 12 premature infants with proven or presumed sepsis during the first month of life. Eleven of 12 patients received netilmicin 2.5 mg/kg intravenously every 12 h while one 770-gram birth weight infant received 2.5 mg/kg every 18 h. Mean steady-state peak and trough concentrations were 8.9 μg/ml and 2.8 μg/ml, respectively. Of twelve patients, 11 had trough serum concentration above 2 μg/ml and four had trough serum concentrations above 3 μg/ml. Mean total body clearance of netilmicin was 0.84 ml/min/kg. The mean clearance of 0.72 ml/min/kg was substantially lower in patients with a mean postnatal age of 2.7 days than the clearance of 1.10 ml/min/kg in patients with a mean postnatal age of 23 days. The mean apparent volume of distribution was 0.63 l/kg; and the mean elimination half-life was 8.6 h. A three-fold interpatient variation in pharmacokinetic parameters was seen. These data suggest the need for careful monitoring of netilmicin serum concentration in premature infants.