Tobramycin pharmacokinetics in very low birth weight infants.

Abstract

Tobramycin is commonly used at a dose of 2.5 mg kg‐1 12h‐1, but this regimen often results in trough serum concentrations exceeding 2 mg l‐ 1. Because of limited data in infants weighing less than 1,000 g at birth, we studied eight newborn infants (gestational age 24‐30 weeks; postnatal age 3 X 4 days; birth weight 0.60‐0.97 kg) at a modified dosing regimen of 2.5 mg kg‐1 18 h‐1 or 3.0 mg kg‐1 24 h‐1. Tobramycin peak and trough serum concentrations ranged from 6.0‐10.8 (7.8 +/‐ 1.5) mg l‐1 and 1.2‐2.4 (1.7 +/‐ 0.4) mg l‐1, respectively. Serum concentration exceeded 2 mg l‐1 in seven of eight patients at 12 h and two of eight at 18 h; none had a trough serum concentration above 2 mg l‐1 at 24 h. Total body clearance ranged from 0.55 to 0.82 (0.69 +/‐ 0.10) ml min‐1 kg‐1; apparent volume of distribution ranged from 0.44 to 0.71 (0.59 +/‐ 0.10) 1 kg‐1; and elimination half‐life ranged from 7.7 to 12.6 (9.9 +/‐ 1.5) h. These data indicate that the modified dosage regimen of 2.5 mg kg‐1 18 h‐1 or 3.0 mg kg‐1 24 h‐1 appears to be more acceptable than the current regimen in achieving effective and safe peak and trough serum concentration of tobramycin in newborn infants weighing less than 1 kg at birth. 1986 The British Pharmacological Society