[Determination of serum concentrations of aminoglycosides in the monitoring of therapy in neonates. I. Gentamycin].

We studied the serum concentrations of gentamicin by radio-immuno-assay in 22 sick prematures (birth weight 1713 +/- 469 g, prenatal age 33 +/- 3 weeks, postnatal age 12 +/- 9 days) receiving 2.5 mg/kg bid. Bactericidal concentrations were present in 91% but only 50% had normal serum concentrations and gentamicin half-lives. Gentamicin half-life decreased significantly (p less than 0.01) with postnatal age but there was no statistically significant correlation between gentamicin serum concentration and gestational age or birth weight. We therefore recommend 1. gentamicin serum concentrations to be monitored routinely in therapy of prematures especially in the first week of life, 2. to expand the dosage interval up to 18 hours (which is about the threefold half-life) in prematures during the first week of life.