Initiation of chloramphenicol therapy in the newborn infant.

To evaluate the ability of a loading dose of chloramphenicol succinate to rapidly, achieve adequate serum concentrations of chloramphenicol, we compared two intravenously administered dosages of chloramphenicol succinate given to initiate treatment. Thirteen premature neonates received an initial dose of 12.5 mg/kg; 26 received a loading dose of 20 mg/kg. Capillary blood samples were obtained at two, four, and 12 hours after the first dose. After the dose of 12.5 mg/kg, 45% of the neonates did not achieve serum concentrations greater than 10 mg/L. After the loading dose of 20 mg/kg, all neonates achieved concentrations greater than 10 mg/L. The peak chloramphenicol concentrations after the 12.5 mg/kg dose was 8.8 +/- 11.2 mg/L (+/- SEM) and after the 20 mg/kg loading dose, 15.9 +/- 0.7 mg/L. The disposition of chloramphenicol was age dependent. Chloramphenicol concentration peaked at four hours in neonates less than or equal to 2 days postnatal age and at two hours in neonates 3 to 55 days postnatal age. Chloramphenicol succinate concentrations were greater in younger than in older neonates at both two and four hours after the dose. We conclude that a loading dose is appropriate when using chloramphenicol succinate in neonates.