Pharmacology of kanamycin in the newborn.

We studied the pharmacologic effects of kanamycin in three groups of newborn infants: group 1--birth weight (BW) less than or equal to 2,000 gm, chronologic age (CA) less than 7 days; group 2--BW greater than 2,000 gm, CA less than 7 days; and group 3--BW greater than 2,000 gm, CA 7 to 28 days. The dose of kanamycin was 15 mg/kg/day, administered in two intramuscular doses. Serum kanamycin levels were measured 15 minutes before the dose and 1/2, 1, 6, and 8 hours after the dose. Infants in group 1 had a mean peak concentration of 18.7 micrograms/ml, those in group 2, 19.6 micrograms/ml, and those in group 3, 15.6 micrograms/ml. The mean peak concentrations varied inversely with chronologic age but were not influenced by birth weight. Mean serum half-life varied inversely with birth weight, gestational age, and chronologic age. We recommend a standard dose of 15 mg/kg/day for newborn infants. Modification of this dose may be required for individual infants.