Once-daily gentamicin dosing in pediatric patients without cystic fibrosis

Pragmatic physiologically-based pharmacokinetic modeling to support clinical implementation of optimized gentamicin dosing in term neonates and infants: proof-of-concept

Introduction

Modeling and simulation can support dosing recommendations for clinical practice, but a simple framework is missing. In this proof-of-concept study, we aimed to develop neonatal and infant gentamicin dosing guidelines, supported by a pragmatic physiologically-based pharmacokinetic (PBPK) modeling approach and a decision framework for implementation.

Methods

An already existing PBPK model was verified with data of 87 adults, 485 children and 912 neonates, based on visual predictive checks and predicted-to-observed pharmacokinetic (PK) parameter ratios. After acceptance of the model, dosages now recommended by the Dutch Pediatric Formulary (DPF) were simulated, along with several alternative dosing scenarios, aiming for recommended peak (i.e., 8-12 mg/L for neonates and 15-20 mg/L for infants) and trough (i.e., <1 mg/L) levels. We then used a decision framework to weigh benefits and risks for implementation.

Results

The PBPK model adequately described gentamicin PK. Simulations of current DPF dosages showed that the dosing interval for term neonates up to 6 weeks of age should be extended to 36-48 h to reach trough levels <1 mg/L. For infants, a 7.5 mg/kg/24 h dose will reach adequate peak levels. The benefits of these dose adaptations outweigh remaining uncertainties which can be minimized by routine drug monitoring.

Conclusion

We used a PBPK model to show that current DPF dosages for gentamicin in term neonates and infants needed to be optimized. In the context of potential uncertainties, the risk-benefit analysis proved positive; the model-informed dose is ready for clinical implementation.

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.

Clinical Pharmacokinetics of Gentamicin in Various Patient Populations and Consequences for Optimal Dosing for Gram-Negative Infections: An Updated Review

Gentamicin is an aminoglycoside antibiotic with a small therapeutic window that is currently used primarily as part of short-term empirical combination therapy. Gentamicin dosing schemes still need refinement, especially for subpopulations where pharmacokinetics can differ from pharmacokinetics in the general adult population: obese patients, critically ill patients, paediatric patients, neonates, elderly patients and patients on dialysis. This review summarizes the clinical pharmacokinetics of gentamicin in these patient populations and the consequences for optimal dosing of gentamicin for infections caused by Gram-negative bacteria, highlighting new insights from the last 10 years. In this period, several new population pharmacokinetic studies have focused on these subpopulations, providing insights into the typical values of the most relevant pharmacokinetic parameters, the variability of these parameters and possible explanations for this variability, although unexplained variability often remains high. Both dosing schemes and pharmacokinetic/pharmacodynamic (PK/PD) targets varied widely between these studies. A gentamicin starting dose of 7 mg/kg based on total body weight (or on adjusted body weight in obese patients) appears to be the optimal strategy for increasing the probability of target attainment (PTA) after the first administration for the most commonly used PK/PD targets in adults and children older than 1 month, including critically ill patients. However, evidence that increasing the PTA results in higher efficacy is lacking; no studies were identified that show a correlation between estimated or predicted PK/PD target attainment and clinical success. Although it is unclear if performing therapeutic drug monitoring (TDM) for optimization of the PTA is of clinical value, it is recommended in patients with highly variable pharmacokinetics, including patients from all subpopulations that are critically ill (such as elderly, children and neonates) and patients on intermittent haemodialysis. In addition, TDM for optimization of the dosing interval, targeting a trough concentration of at least < 2 mg/L but preferably < 0.5–1 mg/L, has proven to reduce nephrotoxicity and is therefore recommended in all patients receiving more than one dose of gentamicin. The usefulness of the daily area under the plasma concentration–time curve for predicting nephrotoxicity should be further investigated. Additionally, more research is needed on the optimal PK/PD targets for efficacy in the clinical situations in which gentamicin is currently used, that is, as monotherapy for urinary tract infections or as part of short-term combination therapy.

Extended Interval Tobramycin Pharmacokinetics in a Pediatric Patient With Primary Ciliary Dyskinesia Presenting With an Acute Respiratory Exacerbation

The pharmacokinetics of tobramycin in patients with ciliary dyskinesia have not been previously reported. A 10-year-old female patient with primary ciliary dyskinesia was admitted to the general pediatrics floor with an acute respiratory exacerbation after several months of worsening lung function that was unresponsive to oral antibiotics. Extrapolating from cystic fibrosis dosing regimens, she was given intravenous tobramycin 320 mg (10.3 mg/kg/day) on admission as a result of concern for a Pseudomonas aeruginosa infection. Two-point pharmacokinetic monitoring revealed a maximum serum concentration (Cmax) of 18.9 mg/L and a 24-hour area under the curve (AUC_0-24hr) of 58.8 (mg × hr)/L, as well as a volume of distribution (Vd) of 0.5 L/kg and an elimination rate (Ke) of 0.34 hr^-1. After a dosage increase to tobramycin 400 mg (12.8 mg/kg/day), pharmacokinetic parameters on 2 assessments were as follows: Vd 0.37 to 0.39 L/kg, Ke 0.33 to 0.39 hr^-1, Cmax 27.8 to 28.7 mg/L, and AUC_0-24h 78.4 to 89.4 (mg × hr)/L. This was the first case report of aminoglycoside pharmacokinetics in a patient with ciliary dyskinesia. The administration of larger doses (up to 12.8 mg/kg/day) of extended-interval tobramycin, similar to the treatment recommendation of at least 10 mg/kg/day for cystic fibrosis patients, was necessary in this patient to achieve serum concentrations that were appropriate for treatment.

Gentamicin Pharmacokinetics and Monitoring in Pediatric Patients with Febrile Neutropenia

BACKGROUND

The pharmacokinetics of gentamicin in pediatric patients with febrile neutropenia is described, and the adequacy of initial dosing of once-daily gentamicin assessed at Queensland's largest Children's Hospital.

METHODS

Data were retrospectively collected from all pediatrics with febrile neutropenia admitted over a 2-year period who had at least 2 gentamicin concentration-time measurements (a paired set within 1 dosing interval). Gentamicin clearance, volume of distribution, area under the concentration-time curve from 0 to 24 hours postdose (AUC0-24), and maximum concentration values were estimated with log-linear regression using each paired set. The percentage of paired sets associated with gentamicin exposure within predefined hospital targets was calculated, and exposure was examined in relation to the bacterial culture status.

RESULTS

Data were collected from 69 patients [median (interquartile range) age 3.7 years (2.2-8.9)] and comprised 121 paired concentration sets characterizing 80 separate admissions. Median (interquartile range) gentamicin clearance and volume of distribution were 8.1 L·h·70 kg (5.8-12.4) and 21.8 L/70 kg (16.9-29.5), respectively. Predefined hospital exposure targets were achieved for both AUC0-24 and maximum concentration for 10% of paired sets; one or the other of these targets were met for 36% of paired sets, and neither target was achieved for 54% of paired sets. Achievement of targets improved with repeated monitoring during the same admission. Median AUC0-24 achieved was significantly higher in patients with a confirmed Gram-negative infection compared with those without 71 (50-91) mg·h·L versus 55 (40.8-67.5) mg·h·L, respectively (P = 0.003). Over the study period, a median gentamicin dose of 10.8 and 6.4 mg/kg was estimated to be necessary to achieve an AUC target of 80 mg·h·L in children ≤10 years and >10 years of age.

CONCLUSIONS

Based on a log-linear method of analysis, current dosing seems to be consistently producing gentamicin exposure below predefined pharmacokinetic targets, suggesting that an increase in the recommended starting dose of gentamicin may be required.

Gentamicin Pharmacokinetics and Monitoring in Pediatric Patients with Febrile Neutropenia

BACKGROUND

The pharmacokinetics of gentamicin in pediatric patients with febrile neutropenia is described, and the adequacy of initial dosing of once-daily gentamicin assessed at Queensland's largest Children's Hospital.

METHODS

Data were retrospectively collected from all pediatrics with febrile neutropenia admitted over a 2-year period who had at least 2 gentamicin concentration-time measurements (a paired set within 1 dosing interval). Gentamicin clearance, volume of distribution, area under the concentration-time curve from 0 to 24 hours postdose (AUC0-24), and maximum concentration values were estimated with log-linear regression using each paired set. The percentage of paired sets associated with gentamicin exposure within predefined hospital targets was calculated, and exposure was examined in relation to the bacterial culture status.

RESULTS

Data were collected from 69 patients [median (interquartile range) age 3.7 years (2.2-8.9)] and comprised 121 paired concentration sets characterizing 80 separate admissions. Median (interquartile range) gentamicin clearance and volume of distribution were 8.1 L·h·70 kg (5.8-12.4) and 21.8 L/70 kg (16.9-29.5), respectively. Predefined hospital exposure targets were achieved for both AUC0-24 and maximum concentration for 10% of paired sets; one or the other of these targets were met for 36% of paired sets, and neither target was achieved for 54% of paired sets. Achievement of targets improved with repeated monitoring during the same admission. Median AUC0-24 achieved was significantly higher in patients with a confirmed Gram-negative infection compared with those without 71 (50-91) mg·h·L versus 55 (40.8-67.5) mg·h·L, respectively (P = 0.003). Over the study period, a median gentamicin dose of 10.8 and 6.4 mg/kg was estimated to be necessary to achieve an AUC target of 80 mg·h·L in children ≤10 years and >10 years of age.

CONCLUSIONS

Based on a log-linear method of analysis, current dosing seems to be consistently producing gentamicin exposure below predefined pharmacokinetic targets, suggesting that an increase in the recommended starting dose of gentamicin may be required.

Pharmacokinetics and Dosing of Anti-infective Drugs in Patients on Extracorporeal Membrane Oxygenation: A Review of the Current Literature

PURPOSE

Extracorporeal membrane oxygenation (ECMO) is a cardiopulmonary bypass device that is used to temporarily support the most critically ill of patients with respiratory and/or cardiac failure. Infection and its sequelae may be an indication for ECMO or infections may be acquired while on ECMO and are associated with a mortality >50%. Effective therapy requires optimal dosing. However, optimal dosing can be different in patients on ECMO because the ECMO circuit can alter drug pharmacokinetics. This review assessed the current literature for pharmacokinetic data and subsequent dosing recommendations for anti-infective drugs in patients on ECMO.

METHODS

We searched the PubMed and Embase databases (1965 to February 2016) and included case reports, case series, or studies that provided pharmacokinetic data for anti-infective drugs including antibiotics, antifungals, and antivirals being used to treat patients of all age groups on ECMO. Pharmacokinetic parameters and dosing recommendations based on these data are presented.

FINDINGS

The majority of data on this topic comes from neonatal studies of antibiotics from the 1980s and 1990s. These studies generally demonstrate a larger volume of distribution due to ECMO and therefore higher doses are needed initially. More adult data are now emerging, but with a predominance of case reports and case series without comparison with critically ill controls. The available pharmacokinetic analyses do suggest that volume of distribution and clearance are unchanged in the adult population, and therefore dosing recommendations largely remain unchanged. There is a lack of data on children older than 1 year of age. The data support the importance of therapeutic drug monitoring when available in this population of patients.

IMPLICATIONS

This review found reasonably robust dosing recommendations for some drugs and scant or no data for other important anti-infectives. In order to better determine optimal dosing for patients on ECMO, a systematic approach is needed. Approaches that combine ex vivo ECMO experiments, animal studies, specialized pharmacokinetic modeling, and human clinical trials are being developed.

Evaluation of Vancomycin Dosing in Pediatric Cystic Fibrosis Patients

OBJECTIVES

The presence of methicillin-resistant Staphylococcus aureus (MRSA) in cystic fibrosis (CF) patients' sputa is associated with a decline in pulmonary function and increased mortality. Vancomycin is the preferred treatment for MRSA pneumonia in children. No published studies have evaluated the vancomycin dose needed to achieve goal vancomycin trough concentrations (VTCs; 15-20 mg/L) in pediatric patients with CF. The primary objective is to determine whether a vancomycin dosage of 60 mg/kg/day achieves a goal VTC in pediatric CF patients. Secondary objectives include determining the average dosage required to reach a goal VTC and the impact of achieving a goal VTC on estimated glomerular filtration rate (eGFR) and pulmonary function.

METHODS

A retrospective review of pediatric patients with CF who received vancomycin was conducted.

RESULTS

A total of 90 vancomycin treatment courses were analyzed. Standard vancomycin dosing (60 mg/kg/day) achieved goal VTC in 11 courses (12.2%). The mean dosage required to achieve a goal VTC for all courses was 70.6 ± 16.7 mg/kg/day. Patients who achieved goal VTCs were more often older, weighed more, and had higher serum creatinine concentrations at therapy initiation. On average, a dosage of 70.6 mg/kg/day was required to achieve a goal VTC. Despite dosages up to 120 mg/kg/day, no significant changes in renal function occurred. Achieving a goal VTC had no significant impact on eGFR or pulmonary function during therapy.

CONCLUSIONS

Vancomycin dosing of 60 mg/kg/day does not reliably achieve a VTC of 15 to 20 mg/L in pediatric CF patients. Younger CF patients may require higher vancomycin doses.

Infectious Diseases Pharmacotherapy for Children With Cystic Fibrosis

Cystic fibrosis (CF) affects several organs, most notably the lungs, which become predisposed to infections with potentially severe consequences. Because of physiologic changes and infection characteristics, unique approaches to antimicrobial agent selection, dosing, and administration are needed. To provide optimal acute and long-term care, pediatric health care providers must be aware of these patient features and common approaches to antimicrobial therapy in CF, which can differ significantly from those of other infectious diseases. The purpose of this article is to review common respiratory pathogens, pharmacology of commonly used antimicrobial agents, and unique pharmacokinetics and dosing strategies often used when treating children with CF.