Augmented renal clearance and therapeutic monitoring of β-lactams

Model-Informed Precision Dosing of Imipenem in an Obese Adolescent Patient with Augmented Renal Clearance and History of Schizophrenia

Imipenem is a broad-spectrum antibiotic that has been used in treating severe infections and exhibits a time-dependent PK/PD profile. Its dose should be adjusted based on renal function. However, there is little experience with imipenem dosing in obese adolescent patients with augmented renal clearance (ARC) and history of schizophrenia. This case reported successful dosing of imipenem in an obese adolescent patient with ARC based on therapeutic drug monitoring (TDM) and model-informed precision dosing (MIPD). A 15-year-old male adolescent patient with history of schizophrenia was diagnosed with ventilator-associated pneumonia due to carbapenem-susceptible Klebsiella pneumoniae and received imipenem treatment (0.5 g every 8 hours with a 1-hour infusion). However, the exposure of imipenem was suboptimal due to ARC, and there is no available model for MIPD in this patient. Thus, we utilized prediction error to find a population pharmacokinetic model that fit this patient and ran Maximum a posteriori Bayesian estimation and Monte Carlo simulation based on screened models to predict changes in drug concentrations. The dose of imipenem was adjusted to 0.5 g every 6 hours with a 2-hour infusion, and subsequent TDM revealed that dosing adjustment was accurate and successful. Finally, the patient's status of infection improved. This study will be beneficial to imipenem dosing in similar cases in the future, thereby improving the safety and effectiveness of imipenem or other antibiotics.

Could an Optimized Joint Pharmacokinetic/Pharmacodynamic Target Attainment of Continuous Infusion Piperacillin-Tazobactam Be a Valuable Innovative Approach for Maximizing the Effectiveness of Monotherapy Even in the Treatment of Critically Ill Patients with Documented Extended-Spectrum Beta-Lactamase-Producing Enterobacterales Bloodstream Infections and/or Ventilator-Associated Pneumonia?

(1) Background: Piperacillin-tazobactam represents the first-line option for treating infections caused by full- or multi-susceptible Enterobacterales and/or Pseudomonas aeruginosa in critically ill patients. Several studies reported that attaining aggressive pharmacokinetic/pharmacodynamic (PK/PD) targets with beta-lactams is associated with an improved microbiological/clinical outcome. We aimed to assess the relationship between the joint PK/PD target attainment of continuous infusion (CI) piperacillin-tazobactam and the microbiological/clinical outcome of documented Gram-negative bloodstream infections (BSI) and/or ventilator-associated pneumonia (VAP) of critically ill patients treated with CI piperacillin-tazobactam monotherapy. (2) Methods: Critically ill patients admitted to the general and post-transplant intensive care unit in the period July 2021-September 2023 treated with CI piperacillin-tazobactam monotherapy optimized by means of a real-time therapeutic drug monitoring (TDM)-guided expert clinical pharmacological advice (ECPA) program for documented Gram-negative BSIs and/or VAP were retrospectively retrieved. Steady-state plasma concentrations (Css) of piperacillin and of tazobactam were measured, and the free fractions (f) were calculated according to respective plasma protein binding. The joint PK/PD target was defined as optimal whenever both the piperacillin fCss/MIC ratio was >4 and the tazobactam fCss/target concentration (CT) ratio was > 1 (quasi-optimal or suboptimal whenever only one or none of the two weas achieved, respectively). Multivariate logistic regression analysis was performed for testing variables potentially associated with microbiological outcome. (3) Results: Overall, 43 critically ill patients (median age 69 years; male 58.1%; median SOFA score at baseline 8) treated with CI piperacillin-tazobactam monotherapy were included. Optimal joint PK/PD target was attained in 36 cases (83.7%). At multivariate analysis, optimal attaining of joint PK/PD target was protective against microbiological failure (OR 0.03; 95%CI 0.003-0.27; p = 0.002), whereas quasi-optimal/suboptimal emerged as the only independent predictor of microbiological failure (OR 37.2; 95%CI 3.66-377.86; p = 0.002). (4) Conclusion: Optimized joint PK/PD target attainment of CI piperacillin-tazobactam could represent a valuable strategy for maximizing microbiological outcome in critically ill patients with documented Gram-negative BSI and/or VAP, even when sustained by extended-spectrum beta-lactamase (ESBL)-producing Enterobacterales. In this scenario, implementing a real-time TDM-guided ECPA program may be helpful in preventing failure in attaining optimal joint PK/PD targets among critically ill patients. Larger prospective studies are warranted to confirm our findings.

Augmented Renal Clearance in the Hematology and Oncology Populations: A Scoping Review for Pharmacists

INTRODUCTION

Until recently, interest in renal function has focused on impairment to limit drug toxicity and increase medication safety. Augmented renal clearance (ARC) has been increasingly studied in multiple patient populations, including oncology, and could lead to decreased drug efficacy from faster elimination resulting in subtherapeutic concentrations. This scoping review sought to summarize ARC literature in cancer and identify areas of research to better inform pharmacy practitioners.

DATA SOURCES

Electronic databases were searched for English articles related to augmented/enhanced renal function/clearance following a framework for scoping reviews.

DATA SYNTHESIS

Fourteen articles were analyzed, divided according to article objective: descriptive studies or ARC's impact on pharmacokinetics/pharmacodynamics. ARC was most defined as creatinine clearance >130 mL/min/1.73 m2, reported in 10%-100% of patients. Febrile neutropenia in adult and pediatric patients, and age <50-65 years, hematologic malignancy, and lower serum creatinine in adult patients were notable risk factors for ARC. The impact of ARC has only been evaluated with antimicrobial agents consistently resulting in lower than anticipated trough levels. Identified gaps include: elucidation of ARC's mechanism and associated biomarkers, an inclusive ARC definition for relative renal enhancement, and study of additional drug classes to ascertain the breadth of ARC impact on drug therapy.

CONCLUSIONS

ARC is proving to be a frequent phenomenon in patients with cancer which pharmacists could play a vital role. Further research is needed to better understand the impact of ARC in patient care and a potential need to stage ARC based on degree of renal enhancement to establish specific drug dosing recommendations.

Role of a Real-Time TDM-Based Expert Clinical Pharmacological Advice Program in Optimizing the Early Pharmacokinetic/Pharmacodynamic Target Attainment of Continuous Infusion Beta-Lactams among Orthotopic Liver Transplant Recipients with Documented or Suspected Gram-Negative Infections

(1) Objectives: To describe the attainment of optimal pharmacokinetic/pharmacodynamic (PK/PD) targets in orthotopic liver transplant (OLT) recipients treated with continuous infusion (CI) beta-lactams optimized using a real-time therapeutic drug monitoring (TDM)-guided expert clinical pharmacological advice (ECPA) program during the early post-surgical period. (2) Methods: OLT recipients admitted to the post-transplant intensive care unit over the period of July 2021-September 2023, receiving empirical or targeted therapy with CI meropenem, piperacillin-tazobactam, meropenem-vaborbactam, or ceftazidime-avibactam optimized using a real-time TDM-guided ECPA program, were retrospectively retrieved. Steady-state beta-lactam (BL) and/or beta-lactamase inhibitor (BLI) plasma concentrations (Css) were measured, and the Css/MIC ratio was selected as the best PK/PD target for beta-lactam efficacy. The PK/PD target of meropenem was defined as being optimal when attaining a fCss/MIC ratio > 4. The joint PK/PD target of the BL/BLI combinations (namely piperacillin-tazobactam, ceftazidime-avibactam, and meropenem-vaborbactam) was defined as being optimal when the fCss/MIC ratio > 4 of the BL and the fCss/target concentration (CT) ratio > 1 of tazobactam or avibactam, or the fAUC/CT ratio > 24 of vaborbactam were simultaneously attained. Multivariate logistic regression analysis was performed for testing potential variables that were associated with a failure in attaining early (i.e., at first TDM assessment) optimal PK/PD targets. (3) Results: Overall, 77 critically ill OLT recipients (median age, 57 years; male, 63.6%; median MELD score at transplantation, 17 points) receiving a total of 100 beta-lactam treatment courses, were included. Beta-lactam therapy was targeted in 43% of cases. Beta-lactam dosing adjustments were provided in 76 out of 100 first TDM assessments (76.0%; 69.0% decreases and 7.0% increases), and overall, in 134 out of 245 total ECPAs (54.7%). Optimal PK/PD target was attained early in 88% of treatment courses, and throughout beta-lactam therapy in 89% of cases. Augmented renal clearance (ARC; OR 7.64; 95%CI 1.32-44.13) and MIC values above the EUCAST clinical breakpoint (OR 91.55; 95%CI 7.12-1177.12) emerged as independent predictors of failure in attaining early optimal beta-lactam PK/PD targets. (4) Conclusion: A real-time TDM-guided ECPA program allowed for the attainment of optimal beta-lactam PK/PD targets in approximately 90% of critically ill OLT recipients treated with CI beta-lactams during the early post-transplant period. OLT recipients having ARC or being affected by pathogens with MIC values above the EUCAST clinical breakpoint were at high risk for failure in attaining early optimal beta-lactam PK/PD targets. Larger prospective studies are warranted for confirming our findings.

The clinical application of beta-lactam antibiotic therapeutic drug monitoring in the critical care setting

Critically ill patients have increased variability in beta-lactam antibiotic (beta-lactam) exposure due to alterations in their volume of distribution and elimination. Therapeutic drug monitoring (TDM) of beta-lactams, as a dose optimization and individualization tool, has been recommended to overcome this variability in exposure. Despite its potential benefit, only a few centres worldwide perform beta-lactam TDM. An important reason for the low uptake is that the evidence for clinical benefits of beta-lactam TDM is not well established. TDM also requires the availability of specific infrastructure, knowledge and expertise. Observational studies and systematic reviews have demonstrated that TDM leads to an improvement in achieving target concentrations, a reduction in potentially toxic concentrations and improvement of clinical and microbiological outcomes. However, a small number of randomized controlled trials have not shown a mortality benefit. Opportunities for improved study design are apparent, as existing studies are limited by their inclusion of heterogeneous patient populations, including patients that may not even have infection, small sample size, variability in the types of beta-lactams included, infections caused by highly susceptible bacteria, and varied sampling, analytical and dosing algorithm methods. Here we review the fundamentals of beta-lactam TDM in critically ill patients, the existing clinical evidence and the practical aspects involved in beta-lactam TDM implementation.

Individual target pharmacokinetic/pharmacodynamic attainment rates among meropenem-treated patients admitted to the ICU with hospital-acquired pneumonia

OBJECTIVES

Critical illness reduces β-lactam pharmacokinetic/pharmacodynamic (PK/PD) attainment. We sought to quantify PK/PD attainment in patients with hospital-acquired pneumonia.

METHODS

Meropenem plasma PK data (n = 70 patients) were modelled, PK/PD attainment rates were calculated for empirical and definitive targets, and between-patient variability was quantified [as a coefficient of variation (CV%)].

RESULTS

Attainment of 100% T&gt;4×MIC was variable for both empirical (CV% = 92) and directed (CV% = 33%) treatment.

CONCLUSIONS

Individualization is required to achieve suggested PK/PD targets in critically ill patients.

Evaluation of the Accuracy of Standard Renal Function Equations in Critically Ill Patients with Subarachnoid Hemorrhage

BACKGROUND

Obtaining an accurate estimation of renal function is germane to optimizing care in critically ill patients. However, there is no consensus on the most accurate renal function assessment to utilize in this patient population, particularly in aneurysmal subarachnoid hemorrhage (aSAH) patients. Thus, the objective of this observational study was to determine the comparability of renal function equations to body surface area (BSA)-adjusted 8-h creatinine clearance (CrCl) in aSAH patients.

METHODS

A PubMed search investigated the applicability of various renal function equations in critically ill patient populations. A subset of these equations was compared to BSA-adjusted 8-h CrCl from a previous study with aSAH patients with no evidence of renal dysfunction (admission serum creatinine < 1.5 mg/dL) and no history of chronic kidney disease. Area-under-the-curve (AUC) calculations were completed using serial laboratory measurements to validate preliminary findings.

RESULTS

A total of 14 renal function equations were identified with seven carried forward for further analysis based upon a priori criteria. Seven equations were excluded for various reasons, including lack of available clinical data, redundancy with other equations, and dissimilar patient populations to this study. When directly compared to the BSA-adjusted 8-h CrCl, only the Cockcroft-Gault and BSA-adjusted Cockcroft-Gault equations were not statistically significantly different (P = 0.0886 and P = 0.4805, respectively); all other equations were statistically significantly different (P < 0.0001). Additionally, only 52% and 44% of patients had average values within 20% of the BSA-adjusted 8-h CrCl using the Cockcroft-Gault and BSA-adjusted Cockcroft-Gault equations, respectively. Finally, the AUC calculations corroborated the preliminary findings with similar results in statistical testing for the Cockcroft-Gault and BSA-adjusted Cockcroft-Gault (P = 0.6300 and P = 0.1513, respectively).

CONCLUSIONS

The Cockcroft-Gault equation may be the best renal function equation to assess in critically ill patients diagnosed with aSAH. However, accuracy and consistency in assessing renal function when compared to the BSA-adjusted 8-h CrCl were lacking. Thus, this study suggests the BSA-adjusted 8-h CrCl may be the most appropriate assessment of renal function in patients with aSAH.

Current Ceftriaxone Dose Recommendations are Adequate for Most Critically Ill Children: Results of a Population Pharmacokinetic Modeling and Simulation Study

Background and Objective

Ceftriaxone is a cornerstone antibiotic for critically ill children with severe infections. Despite its widespread use, information on the pharmacokinetics of ceftriaxone is lacking in this population. We aimed to determine ceftriaxone pharmacokinetics in critically ill children and to propose ceftriaxone dosing guidelines resulting in adequate target attainment using population pharmacokinetic modeling and simulation.

Methods

Critically ill children (aged 0–18 years) treated with intravenous ceftriaxone (100 mg/kg once daily, infused in 30 minutes) and a central or arterial line in place were eligible. Opportunistic blood sampling for total and unbound ceftriaxone concentrations was used. Population pharmacokinetic analysis was performed using non-linear mixed-effects modeling on NONMEM™ Version 7.4.3. Simulations were performed to select optimal doses using probability of target attainment for two pharmacokinetic targets of the minimum inhibitory concentration (MIC) reflecting the susceptibility of pathogens (f T > MIC 100% and fT > 4 × MIC 100%).

Results

Two hundred and five samples for total and 43 time-matched samples for unbound plasma ceftriaxone concentrations were collected from 45 patients, median age 2.5 (range 0.1–16.7) years. A two-compartment model with bodyweight as the co-variate for volume of distribution and clearance, and creatinine-based estimated glomerular filtration rate as an additional covariate for clearance, best described ceftriaxone pharmacokinetics. For a typical patient (2.5 years, 14 kg) with an estimated glomerular filtration rate of 80 mL/min/1.73 m², the current 100-mg/kg once-daily dose results in a probability of target attainment of 96.8% and 60.8% for a MIC of 0.5 mg/L and 4 × MIC (2 mg/L), respectively, when using fT > MIC 100% as a target. For a 50-mg/kg twice-daily regimen, the probability of target attainment was 99.9% and 93.4%, respectively.

Conclusions

The current dosing regimen of ceftriaxone provides adequate exposure for susceptible pathogens in most critically ill children. In patients with an estimated glomerular filtration rate of > 80 mL/min/1.73 m² or in areas with a high prevalence of less-susceptible pathogens (MIC ≥ 0.5 mg/L), a twice-daily dosing regimen of 50 mg/kg can be considered to improve target attainment.

Clinical Trial Registration

POPSICLE study (ClinicalTrials.gov, NCT03248349, registered 14 August, 2017), PERFORM study (ClinicalTrials.gov, NCT03502993, registered 19 April, 2018).

Supplementary Information

The online version contains supplementary material available at 10.1007/s40262-021-01035-9.

Augmented renal clearance: a retrospective, cohort study of urinary creatinine clearance in critically ill patients in the United Kingdom

OBJECTIVE

Augmented renal clearance (ARC) is associated with sub-therapeutic antibiotic, anti-epileptic, and anticoagulant serum concentrations leading to adverse patient outcomes. We aimed to describe the prevalence and associated risk factors for ARC development in a large, single-centre cohort in the United Kingdom.

METHODS

We conducted a retrospective observational study of critically unwell patients admitted to intensive care between 2014 and 2016. Urinary creatinine clearance was used to determine the ARC prevalence during the first 7 days of admission. Repeated measures logistic regression was used to determine risk factors for ARC development.

RESULTS

The ARC prevalence was 47.0% (95% confidence interval [95%CI]: 44.3%-49.7%). Age, sex, Acute Physiology and Chronic Health Evaluation (APACHE) II score, and sepsis diagnosis were significantly associated with ARC. ARC was more prevalent in younger vs. older (odds ratio [OR] 0.95 [95%CI: 0.94-0.96]), male vs. female (OR 0.32 [95%CI: 0.26-0.40]) patients with lower vs. higher APACHE II scores (OR 0.94 [95%CI: 0.92-0.96]).

CONCLUSIONS

This patient group probably remains unknown to many clinicians because measuring urinary creatinine clearance is not usually indicated in this group. Clinicians should be aware of the ARC risk in this group and consider measurement of urinary creatinine clearance.

Ensuring Sufficient Trough Plasma Concentrations for Broad-Spectrum Beta-Lactam Antibiotics in Children With Malignancies: Beware of Augmented Renal Clearance!

Introduction: Broad-spectrum beta-lactams are commonly prescribed for empirical or selective treatment of bacterial infections in children with malignancies. In the immunocompromised, appropriate concentration exposure is crucial to ensure antimicrobial efficacy. Augmented renal clearance (ARC) is increasingly recognized in this population, and raises concern for unmet concentration targets. We conducted a retrospective evaluation of meropenem and piperacillin exposure in our hospital's pediatric hematology-oncology patients. Materials and Methods: We compared trough levels of meropenem and piperacillin in a cohort of unselected pediatric hematology-oncology patients stratified based on their estimated renal function as decreased, normal or with ARC, and on their neutrophil count. Results: Thirty-two children provided a total of 51 meropenem and 76 piperacillin samples. On standard intermittent intravenous regimen, 67% of all trough plasma concentrations were below targeted concentrations. In neutropenic children with bacterial infection, all meropenem and 60% of piperacillin levels were below target. Nearly two-thirds of total samples came from children with ARC. In these patients, antimicrobial exposure was insufficient in 85% of cases (compared to 36% in the decreased or normal renal function groups), despite a dosage sometimes exceeding the maximum recommended daily dose. Under continuous infusion of piperacillin, only 8% of plasma levels were insufficient. Discussion: Intermittent administration of meropenem and piperacillin often fails to ensure sufficient concentration exposure in children treated for malignancies, even at maximal recommended daily dosage. This can in part be attributed to ARC. We recommend thorough assessment of renal function, resolute dosage adjustment, continuous infusion whenever possible and systematic therapeutic drug monitoring.

Antibiotic therapy as personalized medicine - general considerations and complicating factors

The discovery of antibiotic drugs is considered one of the previous century's most important medical discoveries (Medicine's 10 greatest discoveries. New Haven, CT: Yale University Press, 1998: 263). Appropriate use of antibiotics saves millions of lives each year and prevents infectious complications for numerous people. Still, infections kill unacceptable many people around the world, even in developed countries with easy access to most antibiotic drugs. Optimal use of antibiotics is dependent on the identification of primary and secondary focus, and knowledge on which pathogens to expect in a specific infectious syndrome and information on general patterns of regional antibiotic resistance. Furthermore, sampling for microbiological analysis, knowledge of patient immune status and organ functions, travel history, pharmacokinetics and -dynamics of the different antibiotics and possible biofilm formation are among several factors involved in antibiotic therapy of infectious diseases. The present review aims at describing important considerations when using antibacterial antibiotics and to describe how this is becoming substantially more personalized. The parameters relevant in considering the optimal use of antibiotics to treat infections are shown in Fig. 1 - leading to the most relevant antibiotic therapy for that specific patient. To illustrate this subject, the present review's focus will be on challenges with optimal dosing of antibiotics and risks of underdosing. Especially, in cases highly challenging for achieving the aimed antibiotic effect against bacterial infections - this includes augmented renal clearance (ARC) in sepsis, dosing challenges of antibiotics in pregnancy and against biofilm infections.

Augmented renal clearance

Adding to the complexity of caring for critically ill patients is the fact that many of them have a creatinine clearance that exceeds 130 mL/min/1.73 m². This phenomenon, termed augmented renal clearance (ARC), has only recently been widely recognized and its pathogenesis remains incompletely understood. However, ARC has been shown to result in increased dose requirements for drugs that are primarily eliminated by renal excretion, including many antimicrobial agents and enoxaparin. Recognition of ARC is hampered by the fact that the standard creatinine-based equations used to estimate renal function are not accurate in this clinical setting and the diagnosis is best established using both serum and urine creatinine measurements to calculate clearance. So a high index of clinical suspicion and awareness is usually required before this step is taken to confirm the diagnosis of ARC.

Augmented Renal Clearance in Patients With Febrile Neutropenia is Associated With Increased Risk for Subtherapeutic Concentrations of Vancomycin

BACKGROUND

Augmented renal clearance (ARC) has frequently been observed in critically ill patients. The risk factors for ARC in patients, including those in the general ward, and their influences on vancomycin (VCM) treatment remain unclear. The aims of this study were to investigate the risk factors for ARC and to evaluate the influence of ARC on the pharmacokinetic parameters of VCM.

METHODS

This study included a total of 292 patients with VCM treatment who had normal serum creatinine concentrations. ARC was defined by an estimated creatinine clearance ≥130 mL·min·1.73 m. The risk factors for ARC were determined with stepwise logistic regression analysis. The pharmacokinetic parameters of VCM were estimated through the Bayesian method using a 2-compartment model.

RESULTS

ARC was observed in 48 patients (16.4%). Age ≤65 years [odds ratio (OR): 5.77; 95% CI: 2.89-11.97; P < 0.0001], brain injury (OR: 5.11; 95% CI: 1.49-17.57; P = 0.0086), febrile neutropenia (OR: 2.76; 95% CI: 1.11-6.67; P = 0.0254), and a mean volume of infusion fluid ≥1500 mL/d (OR: 2.53; 95% CI: 1.27-5.16; P = 0.0091) were independent risk factors for the occurrence of ARC. The patients with ARC exhibited higher VCM clearance values than the non-ARC patients. The median trough serum concentrations of VCM were 7.4 (interquartile range: 5.2-11.6) mcg/mL in the ARC patients and 12.2 (8.9-16.3) mcg/mL in the non-ARC patients (P < 0.0001). Subtherapeutic trough concentrations of VCM (<10.0 mcg/mL) were found in 68.8% of the ARC patients and in 32.8% of the non-ARC patients (P < 0.0001).

CONCLUSIONS

This observational study investigated the influence of febrile neutropenia on the emergency of ARC for the first time. ARC was strongly associated with VCM pharmacokinetics, and two-thirds of the ARC patients had subtherapeutic VCM concentrations. In patients with ARC, individualized dosing regimens are required to achieve the target trough concentration.

Application of vancomycin in patients with varying renal function, especially those with augmented renal clearance

CONTEXT

Augmented renal clearance (ARC) refers to enhanced renal elimination of circulating solute, and has attracted wide attention in recent years.

OBJECTIVE

This study evaluates the effects of ARC on serum vancomycin concentration in patients administered vancomycin.

MATERIALS AND METHODS

This was a retrospective study in patients receiving vancomycin treatment at a dose of 1000 mg in every 12 h and undergoing serum monitoring admitted over a 2-year period (May 2013 to May 2015), in order to estimate the influence of ARC on serum vancomycin concentration. In this study, statistical comparisons were made on the results from patients grouped according to creatinine clearance (CL_cr).

RESULTS

One hundred forty-eight patients were enrolled in our study. The results showed that ARC patients were significantly younger, with a significantly lower S_cr and higher GFR. The CL_cr and steady-state trough concentrations of serum vancomycin exhibited a logarithmic correlation (Rs = -0.699, R²=0.488, p < 0.01) in the patients included in our study. The trough vancomycin concentrations of 62.9% patients in high CL_cr group were under 10 μg/mL.

DISCUSSION AND CONCLUSION

Since ARC was significantly associated with subtherapeutic serum vancomycin concentration, it was necessary to devise adjusted dosage regimens for these patients based on their CL_cr.

Optimizing dosing of antibiotics in critically ill patients

PURPOSE OF REVIEW

Recent studies suggest that contemporary antibiotic dosing is unlikely to achieve best outcomes for critically ill patients because of extensive pharmacokinetic variability and altered pharmacodynamics. Dose adaptation is considered quite challenging because of unpredictable dose-exposure relationships. Consequently, individualization of antibiotic dosing has been advocated. Herein, we describe recent developments in the optimization of antibiotic dosing in the critically ill.

RECENT FINDINGS

Conventional doses of many antibiotics frequently result in sub or supratherapeutic exposures in the critically ill. Clinical studies continue to illustrate that dose-exposure relationships are highly variable in severely ill patients. Dose optimization based on pharmacokinetic/pharmacodynamic principles can effectively improve antibiotic exposure. Therapeutic drug monitoring (TDM) with adaptive feedback is likely to be the most robust approach to optimize dosing for individual patients. This more accurate approach to dosing is made possible with the user-friendly dosing software that is emerging.

SUMMARY

The scope of TDM is broadening from the traditional focus on prevention of toxicity, to include optimization of antibiotic exposure thereby improving patient outcomes. However, the evidence relating TDM practice with improved clinical outcome remains limited. Well designed, multicentre, randomized controlled studies are warranted.

Uncertainty in Antibiotic Dosing in Critically Ill Neonate and Pediatric Patients: Can Microsampling Provide the Answers?

PURPOSE

With a decreasing supply of antibiotics that are effective against the pathogens that cause sepsis, it is critical that we learn to use currently available antibiotics optimally. Pharmacokinetic studies provide an evidence base from which we can optimize antibiotic dosing. However, these studies are challenging in critically ill neonate and pediatric patients due to the small blood volumes and associated risks and burden to the patient from taking blood. We investigate whether microsampling, that is, obtaining a biologic sample of low volume (<50 μL), can improve opportunities to conduct pharmacokinetic studies.

METHODS

We performed a literature search to find relevant articles using the following search terms: sepsis, critically ill, severe infection, intensive care AND antibiotic, pharmacokinetic, p(a)ediatric, neonate. For microsampling, we performed a search using antibiotics AND dried blood spots OR dried plasma spots OR volumetric absorptive microsampling OR solid-phase microextraction OR capillary microsampling OR microsampling. Databases searched include Web of Knowledge, PubMed, and EMbase.

FINDINGS

Of the 32 antibiotic pharmacokinetic studies performed on critically ill neonate or pediatric patients in this review, most of the authors identified changes to the pharmacokinetic properties in their patient group and recommended either further investigations into this patient population or therapeutic drug monitoring to ensure antibiotic doses are suitable. There remain considerable gaps in knowledge regarding the pharmacokinetic properties of antibiotics in critically ill pediatric patients. Implementing microsampling in an antibiotic pharmacokinetic study is contingent on the properties of the antibiotic, the pathophysiology of the patient (and how this can affect the microsample), and the location of the patient. A validation of the sampling technique is required before implementation.

IMPLICATIONS

Current antibiotic regimens for critically ill neonate and pediatric patients are frequently suboptimal due to a poor understanding of altered pharmacokinetic properties. An assessment of the suitability of microsampling for pharmacokinetic studies in neonate and pediatric patients is recommended before wider use. The method of sampling, as well as the method of bioanalysis, also requires validation to ensure the data obtained reflect the true result.

Personalised beta-lactam therapy: basic principles and practical approach

Bacterial infections are potentially life-threatening diseases requiring effective antibiotic treatment right from the outset to achieve a favourable prognosis. Therapeutic success depends on the susceptibility of the bacterial pathogen, determined by the minimum inhibitory concentration (MIC), and the concentration of the antibiotic at the focus of infection, which is influenced by drug metabolism and pharmacokinetic (PK) factors. Beta-lactams are time-dependent antibiotics. Bacterial killing correlates with the duration of the drug concentration above the MIC of the pathogen. Critical illness is associated with major PK changes. This may lead to unexpected drug concentrations and unpredictable dose requirements differing significantly from standard dosages. Emerging dosing strategies are therefore based on PK/pharmacodynamic (PD) principles. Therapeutic drug monitoring (TDM) is increasingly playing a key role in antibiotic treatment optimisation in general and in beta-lactam therapy, in particular, notably in severely ill patients. Furthermore, evidence of the superiority of continuous beta-lactam infusions over shorter administration regimens is growing. Target drug concentrations have to be defined, considering MIC values especially in pathogens with limited susceptibility. For reliable TDM results, correct pre-analytical sample handling is indispensable. Personalised, TDM-guided therapy currently offers the most promising approach to assuring that beta-lactam treatment is effective, especially in critically ill patients.