Pharmacologic evaluation of gentamicin in newborn infants

Suitable antibacterial levels were achieved in sera of newborn infants following individual doses of gentamicin of 1.5-2.5 mg/kg given every 8 or 12 hr. The larger dose gave more predictable levels within the desired therapeutic range, and the highest individual level in serum was below the known toxic range. Significant accumulation was not observed with multiple doses for up to 12 days of therapy. Levels in serum and half-life values after intravenous infusion of gentamicin over a 2-hr period were similar to those after intramuscular administration. Excretion was primarily by glomerular filtration and correlated better with postnatal age than with body weight. Gentamicin was detectable in cerebrospinal fluid following intramuscular administration. The level in spinal fluid was dependent on dose, time after administration, and degree of meningeal inflammation. Intrathecal instillation resulted in higher levels in spinal fluid. The efficacy of gentamicin was evaluated in 81 neonatal infants. Fifty-five infants responded promptly, 20 infants responded moderately well, and a poor response was observed in six infants. There was no evidence of acute hematologic or renal toxicity in the 74 infants studied.