Gentamicin trough levels using a simplified extended-interval dosing regimen in preterm and term newborns

Abstract

To evaluate a simplified gentamicin extended-interval dosing regimen in a large cohort of preterm and term newborns, we conducted a retrospective cohort study over a 4-year period. All inborn newborns who received gentamicin for the first episode of suspected or proven sepsis were eligible. Newborns received 4 mg/kg gentamicin intravenously 24-hourly, except for those at <28 weeks of gestation who received gentamicin 36-hourly. Trough levels were taken before the third dose and considered non-toxic if ≤2 μg/mL. Infants were analysed in gestational age subgroups: <28 weeks, 28–31 weeks, 32–35 weeks, 36–39 weeks and ≥40 weeks. Newborns who received indomethacin co-medication were analysed separately. Nine hundred ninety-three newborns, gestational age range 23⁺²–42⁺¹ weeks, birth weight range 397–5936 g, were included. The median (interquartile range (IQR)) gentamicin trough level for all newborns was 1.3 μg/mL (0.8–1.7). Ninety per cent of newborns had non-toxic trough levels. The incidence of trough levels >2 μg/mL was between 2.2 and 9.7 % in all subgroups except for infants born at 28–31 weeks of gestation, where 21.7 % of trough levels were >2 μg/mL. Indomethacin co-medication significantly increased the median gentamicin trough level in preterm infants at <32 weeks of gestation.

Conclusion: This study demonstrates that simplified gentamicin dosage regimens are feasible. Prospective evaluations are required to establish safety profiles.