[Influence of gestational age and postnatal kidney maturation on the kinetics of gentamicin]

The current schedule for gentamicin administration to newborn infants, in doses of 2.5 mg/kg every twelve hours during the first week of life was evaluated in pre-term newborns under 35 weeks of gestational age (GA). Pharmacokinetic studies in steady state conditions were performed at the third and seventh days of therapy (periods A and B respectively) in nine pre-term (GA 30 to 34 weeks) and ten full-term newborns. Minimal gentamicin blood concentrations at period A were 1.96 +/- 0.32 micrograms/ml in term newborns and 2.51 +/- 0.48 micrograms/ml in pre-term infants (p less than 0.005) and, at period B, 1.49 +/- 0.37 micrograms/ml and 2.33 +/- 0.34 respectively (p less than 0.001). Gentamicin excretion showed good correlations with gestational age (r: 0.654; p less than 0.005) and creatinine clearance (r: 0.628; p less than 0.005).