Gentamicin Dosing in Neonates with Normal Renal Function: Trough and Peak Levels

Population pharmacokinetics and dose rationale for aciclovir in term and pre-term neonates with herpes

Aciclovir is considered the first-line treatment against Herpes simplex virus (HSV) infections in new-borns and infants. As renal excretion is the major route of elimination, in renally-impaired patients, aciclovir doses are adjusted according to the degree of impairment. However, limited attention has been given to the implications of immature renal function or dysfunction due to the viral disease itself. The aim of this investigation was to characterize the pharmacokinetics of aciclovir taking into account maturation and disease processes in the neonatal population. Pharmacokinetic data obtained from 2 previously published clinical trials (n = 28) were analyzed using a nonlinear mixed effects modeling approach. Post-menstrual age (PMA) and creatinine clearance (CLCR) were assessed as descriptors of maturation and renal function. Simulation scenarios were also implemented to illustrate the use of pharmacokinetic data to extrapolate efficacy from adults. Aciclovir pharmacokinetics was described by a one-compartment model with first-order elimination. Body weight and diagnosis (systemic infection) were statistically significant covariates on the volume of distribution, whereas body weight, CLCR and PMA had a significant effect on clearance. Median clearance varied from 0.2 to 1.0 L/h in subjects with PMA <34 or ≥34 weeks, respectively. Population estimate for volume of distribution was 1.93 L with systemic infection increasing this value by almost 3-fold (2.67 times higher). A suitable model parameterization was identified, which discriminates the effects of developmental growth, maturation, and organ function. Exposure to aciclovir was found to increase with decreasing PMA and renal function (CLCR), suggesting different dosing requirement for pre-term neonates.

Evaluating Adherence to Therapeutic Drug Monitoring Guidelines for Gentamicin in Neonatal Care: A Retrospective Study at the Maternity and Children's Hospital in Makkah

In this study, we assess healthcare providers' adherence to therapeutic drug monitoring (TDM) guidelines for gentamicin in neonates. Conducted at the Maternity and Children's Hospital in Makkah, Saudi Arabia, from July 2020 to July 2022, it retrospectively analyzed the compliance of healthcare workers in managing neonates treated with gentamicin. Covering 410 neonates, primarily diagnosed with respiratory distress (56%) and sepsis (32%), the study revealed that while a majority of trough and peak levels conformed to guidelines, substantial deviations were noted in cases of respiratory distress. This underlines the necessity for targeted TDM strategies, particularly in managing respiratory distress in neonates, to ensure optimal treatment efficacy and safety. The findings urge stringent compliance with TDM guidelines, emphasizing personalized approaches in neonatal gentamicin therapy for improved healthcare outcomes.

Is fat-free mass-based gentamicin dosing regimen preferable than whole-body weight in neonates?

Importance

Body fluid dynamics and renal maturation status vary during the neonatal period. We hypothesized that differences in peak and trough gentamicin concentrations could be expected.

Objective

To predict the peak and trough gentamicin concentrations in critically ill neonates and to predict the changes in the predicted peak plasma concentrations of gentamicin following fat-free mass dosing.

Methods

Critically ill neonates that received gentamicin and have gentamicin concentration measured were recruited. Fat mass was estimated using skinfold thicknesses. Changes in the peak plasma concentrations (C_max) using whole-body weight (estimated using the current dosing regimen) and predicted concentrations following the fat-free mass-based dosing were the outcome measures.

Results

Eighty-nine critically ill neonates were recruited. Sub-therapeutic C_max was estimated using the current dosing regimen in 32.6%, and 22.5% neonates following the first and second doses of gentamicin. Preterm neonates had significantly higher fat mass compared to term neonates. All except one had C_max above 12 μg/ml after the first dose and all had after the second gentamicin dose following the predicted fat-free mass-based gentamicin dosing. The recommended doses are as follows: extreme preterm: 7.95 mg/kg every 48 h; very preterm: 7.30 mg/kg every 36-48 h; late preterm: 5.90 mg/kg every 36-48 h; and term neonates at 5.10 mg/kg every 24 h.

Interpretation

Fat-free mass dosing may be considered for obtaining optimal therapeutic effects in the neonatal population.

Evaluation of Dosing Guidelines for Gentamicin in Neonates and Children

Although aminoglycosides are frequently prescribed to neonates and children, the ability to reach effective and safe target concentrations with the currently used dosing regimens remains unclear. This study aims to evaluate the target attainment of the currently used dosing regimens for gentamicin in neonates and children. We conducted a retrospective single-center cohort study in neonates and children receiving gentamicin between January 2019 and July 2022, in the Beatrix Children's Hospital. The first gentamicin concentration used for therapeutic drug monitoring was collected for each patient, in conjunction with information on dosing and clinical status. Target trough concentrations were ≤1 mg/L for neonates and ≤0.5 mg/L for children. Target peak concentrations were 8-12 mg/L for neonates and 15-20 mg/L for children. In total, 658 patients were included (335 neonates and 323 children). Trough concentrations were outside the target range in 46.2% and 9.9% of neonates and children, respectively. Peak concentrations were outside the target range in 46.0% and 68.7% of neonates and children, respectively. In children, higher creatinine concentrations were associated with higher gentamicin trough concentrations. This study corroborates earlier observational studies showing that, with a standard dose, drug concentration targets were met in only approximately 50% of the cases. Our findings show that additional parameters are needed to improve target attainment.

Gentamicin Pharmacokinetics and Optimal Dosage in Infant Patients: A Case Report and Literature Review

Gentamicin is an aminoglycoside antibiotic that is mostly used for the pediatric population. While the pediatric population is classified into neonates, infants, children, and adolescents based on developmental or maturational changes, infants are often overlooked in research. Three infant cases receiving gentamicin are presented to illustrate the pharmacokinetics and optimum dosage of gentamicin. Three infant patients received gentamicin (5.6-7.5 mg/kg/day) for urinary tract infections (UTIs) or bacteremia caused by Enterobacter aerogenes. The trough (Cmin) and peak (Cpeak) concentrations of gentamicin were 0.2-1.8 and 8.9 mg/L, respectively. The Cmin of a patient receiving gentamicin at 9.0 mg/kg/day was 3.3 mg/L, and the patient showed a decrease in urinary volume. The other two patients fully recovered from the infection and did not experience any adverse events. Additionally, we reviewed three studies regarding infant patients receiving gentamicin. The studies used gentamicin therapy for Gram-negative pathogen infections and UTIs caused by Escherichia coli and Enterococcus faecalis. The Cmin and Cpeak of patients receiving gentamicin at 2.2-7.5 mg/kg/day were 0.58-2.15 mg/kg and 4.67-8.88 mg/L, respectively. All patients were cured without any adverse events. Gentamicin dosages below 7.5 mg/kg/day may be effective and safe for use in infant patients. However, the optimal dosing regimen of gentamicin in infant patients is controversial, and limited data are available.

Physiologically-based pharmacokinetic modelling and dosing evaluation of gentamicin in neonates using PhysPK

Each year, infections caused around the 25% of neonatal deaths. Early empirical treatments help to reduce this mortality, although optimized dosing regimens are still lacking. The aims were to develop and validate a gentamicin physiologically-based pharmacokinetic (PBPK) model and then potentially explore dosing regimens in neonates using pharmacokinetic and pharmacodynamic criteria. The PBPK model developed consisted of 2 flow-limited tissues: kidney and other tissues. It has been implemented on a new tool called PhysPK, which allows structure reusability and evolution as predictive engine in Model-Informed Precision Dosing (MIPD). Retrospective pharmacokinetic information based on serum levels data from 47 neonates with gestational age between 32 and 39 weeks and younger than one-week postnatal age were used for model validation. The minimal PBPK model developed adequately described the gentamicin serum concentration-time profile with an average fold error nearly 1. Extended interval gentamicin dosing regimens (6 mg/kg q36h and 6 mg/kg q48h for term and preterm neonates, respectively) showed efficacy higher than 99% with toxicity lower than 10% through Monte Carlo simulation evaluations. The gentamicin minimal PBPK model developed in PhysPK from literature information, and validated in preterm and term neonates, presents adequate predictive performance and could be useful for MIPD strategies in neonates.