Vancomycin pharmacokinetics were studied in nine premature infants. Infants 
weighing less than 1,000 gm had significantly larger volumes of drug 
distribution and consequently longer drug half-lives than larger premature 
infants, regardless of postconceptual or actual age. These differences alter the 
vancomycin dosing recommendations in these two groups of premature infants. We 
recommend initial dosage regimens consisting of a loading dose of vancomycin of 
25 mg/kg followed by doses of 15 mg/kg every 12 hours for infants with weights 
less than 1,000 gm. Infants weighing over 1,000 gm should receive 10 mg/kg every 
12 hours, with a loading dose of 12.5 mg/kg. Serum vancomycin concentration 
should be monitored, however, for final optimization of therapy.