AIMThis study aims to investigate the clinical and demographic factors influencing gentamicin pharmacokinetics in a large cohort of unselected premature and term newborns and to evaluate optimal regimens in this population.
METHODSAll gentamicin concentration data, along with clinical and demographic characteristics, were retrieved from medical charts in a Neonatal Intensive Care Unit over 5 years within the frame of a routine therapeutic drug monitoring programme. Data were described using non-linear mixed-effects regression analysis ( NONMEM®).
RESULTSA total of 3039 gentamicin concentrations collected in 994 preterm and 455 term newborns were included in the analysis. A two compartment model best characterized gentamicin disposition. The average parameter estimates, for a median body weight of 2170 g, were clearance (CL) 0.089 l h −1 (CV 28%), central volume of distribution (Vc) 0.908 l (CV 18%), intercompartmental clearance (Q) 0.157 l h −1 and peripheral volume of distribution (Vp) 0.560 l. Body weight, gestational age and post-natal age positively influenced CL. Dopamine co-administration had a significant negative effect on CL, whereas the influence of indomethacin and furosemide was not significant. Both body weight and gestational age significantly influenced Vc. Model-based simulations confirmed that, compared with term neonates, preterm infants need higher doses, superior to 4 mg kg −1 , at extended intervals to achieve adequate concentrations.
CONCLUSIONSThis observational study conducted in a large cohort of newborns confirms the importance of body weight and gestational age for dosage adjustment. The model will serve to set up dosing recommendations and elaborate a Bayesian tool for dosage individualization based on concentration monitoring.
WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT• Gentamicin is one of the most frequently administered drugs to neonates for suspected or proven infections.• Therapeutic drug monitoring (TDM) has been highly recommended in the past due to variability in drug disposition.• Very preterm newborns need higher doses and longer dosing intervals than term newborns.
WHAT THIS STUDY ADDS• This study is the largest ever done on an unselected cohort of neonates and confirms the major influence of body weight, gestational and post-natal ages on gentamicin pharmacokinetics.• Our model confirms that recent guidelines for gentamicin dosage decisions are appropriate to reach concentration targets considered effective and safe in neonates.