Insufficient β-lactam concentrations in the early phase of severe sepsis and septic shock

[Clinical practice guidelines for meropenem therapy in neonatal sepsis (2024)]

Meropenem is one of the most widely used special-grade antimicrobial agents in the treatment of neonatal sepsis. However, its irrational use has led to an increasingly severe problem of bacterial multidrug resistance. The guideline was developed following standardized methods and procedures, and provides 12 recommendations specifically addressing 9 clinical issues. The recommendations cover various aspects of meropenem use in neonates, including timing of administration, recommended dosage, extended infusion, monitoring and assessment, antimicrobial adjustment strategies, treatment duration, and treatment strategies for carbapenem-resistant Enterobacteriaceae infections. The aim of the guideline is to provide evidence-based recommendations and guidance for the rational use of meropenem in neonates with sepsis.

Cefepime-Associated Neurotoxicity in a Pediatric Patient With Stage V Chronic Kidney Disease

Background: Studies in adult patients suggest cefepime can cause neurotoxicity, including disorientation, seizures, and coma, particularly when present at high concentrations. Patients with underlying kidney dysfunction or central nervous system anomalies are at particularly high risk. There is a relative paucity of pediatric literature on the neurotoxic effects of cefepime. Case Report: Herein is reported the case of a 2-year-old patient with chronic kidney disease receiving cefepime for Serratia marcescens bacteremia who experienced agitation, tremor, and inconsolability in the setting of an elevated cefepime trough that improved with cefepime discontinuation alone. Conclusions: Pediatric patients with acute and chronic kidney disease are at risk of cefepime-related neurologic changes. Therapeutic drug monitoring for cefepime in patients with kidney dysfunction or baseline neurologic abnormalities may help inform appropriate antimicrobial dosing and avoidance of toxicity.

Ampicillin Pharmacokinetics in Peripartum and Laboring Women

OBJECTIVE

 Ampicillin is used for multiple peripartum indications including prevention of neonatal group B streptococcus (GBS) and treatment of chorioamnionitis. Despite its widespread use in obstetrics, existing pharmacokinetic data for ampicillin do not address contemporary indications or dosing paradigms for this population. We sought to characterize the pharmacokinetic profile of ampicillin administered to laboring women.

STUDY DESIGN

 Using whole blood dried blood spot sampling technique, maternal blood samples were collected at specified times from 31 women receiving intravenous (IV) ampicillin for peripartum indications. Women received either a 2-g loading dose with 1-g administered every 4 hours (GBS) or 2-g every 6 hours (chorioamnionitis). Pharmacokinetics were analyzed via a population approach with nonlinear mixed-effect modeling.

RESULTS

 The data were best described by a two-compartment model with first-order elimination, with the following whole blood parameters: central volume of distribution (V1), 75.2 L (95% confidence interval [CI]: 56.3-93.6); clearance (CL), 82.4 L/h (95% CI: 59.7-95.7); intercompartmental clearance (Q), 20.9 L/h (95% CI: 16.2-38.2); and peripheral volume of distribution (V2), 61.1 L (95% CI: 26.1-310.5). Interpatient variation in CL and V1 was large (42.0 and 56.7%, respectively). Simulations of standard dosing strategies demonstrated over 98% of women are predicted to achieve an estimated free plasma concentration above mean inhibitory concentration (MIC) of 0.5 μg/mL for more than 50% of the dosing interval.

CONCLUSION

 Although large variation in the pharmacokinetics of ampicillin in pregnant women exists, as predicted by our model, current standard dosing strategies achieve adequate exposure for GBS in nearly all patients.

KEY POINTS

· IV ampicillin is widely used in obstetrics.. · Pharmacokinetic studies are lacking.. · Ampicillin pharmacokinetics were established.. · Ampicillin clearance and volume of distribution are high.. · Current ampicillin dosing strategies are sufficient..

Impact of Beta-Lactam Target Attainment on Resistance Development in Patients with Gram-Negative Infections

BACKGROUND

The objective was to identify associations between beta-lactam pharmacokinetic/pharmacodynamic (PK/PD) targets and Gram-negative bacteria resistance emergence in patients.

METHODS

Retrospective data were collected between 2016 to 2019 at the University of Florida Health-Shands Hospital in Gainesville, FL. Adult patients with two Gram-negative isolates receiving cefepime, meropenem, or piperacillin-tazobactam and who had plasma beta-lactam concentrations were included. Beta-lactam exposures and time free drug concentrations that exceeded minimum inhibitory concentrations (ƒT > MIC), four multiples of MIC (ƒT > 4× MIC), and free area under the time concentration curve to MIC (ƒAUC/MIC) were generated. Resistance emergence was defined as any increase in MIC or two-fold increase in MIC. Multiple regression analysis assessed the PK/PD parameter impact on resistance emergence.

RESULTS

Two hundred fifty-six patients with 628 isolates were included. The median age was 58 years, and 59% were males. Cefepime was the most common beta-lactam (65%) and Pseudomonas aeruginosa the most common isolate (43%). The mean daily ƒAUC/MIC ≥ 494 was associated with any increase in MIC (p = 0.002) and two-fold increase in MIC (p = 0.004). The daily ƒAUC/MIC ≥ 494 was associated with decreased time on antibiotics (p = 0.008). P. aeruginosa was associated with any increase in MIC (OR: 6.41, 95% CI [3.34-12.28]) or 2× increase in MIC (7.08, 95% CI [3.56-14.07]).

CONCLUSIONS

ƒAUC/MIC ≥ 494 may be associated with decreased Gram-negative resistance emergence.

Swedish multicentre study of target attainments with β-lactams in the ICU: which MIC parameter should be used?

BACKGROUND

Therapeutic drug monitoring (TDM) has been suggested to optimize antimicrobial target attainment, typically using 100%T>MIC, in β-lactam treatment in the ICU. The MIC parameter used in this equation is mostly the worst case scenario MIC (MICWCS)-the highest MIC the empirical treatment should cover. However, the impact of the MIC parameter used in pharmacokinetic/pharmacodynamic calculations has been poorly investigated.

OBJECTIVES

To assess the influence of target attainment rates for two different MIC parameters using actual MICs of the causative pathogens as the primary reference.

METHODS

In a Swedish multicentre study of target attainment for 138 ICU patients treated with β-lactams, the causative pathogen was isolated and subjected to reference MIC testing. Whenever the strain belonged to the WT distribution, we assigned it to the category MICECOFF (epidemiological cut-off value). In the calculations we compared the MICECOFF and the MICWCS.

RESULTS

The proportion of patients with target attainment failure for all antibiotics using 100%T>MIC was 45% (95% CI, 37%-53%) for MICWCS and 23% (95% CI, 16%-31%) for MICECOFF. When the target 50%T>4×MIC was used, corresponding attainment failures were 57% (95% CI, 49%-66%) and 25% (95% CI, 17%-32%) for MICWCS and MICECOFF, respectively.

CONCLUSIONS

MICWCS can overestimate target attainment failure. The use of MICWCS could be one reason for the difficulties in establishing a relationship between target failure and mortality in other studies. Based on findings herein, the MICECOFF, which is based on the MIC of the causative pathogen, should be considered a more suitable alternative. When no pathogen is detected, the MICECOFF of likely pathogens according to infection type should be used.

State of the Management of Infections Caused by Multidrug-Resistant Gram-Negative Organisms

In the past decade, the prevalence of multidrug-resistant gram-negative (MDR-GN) bacterial infections has increased significantly, leading to higher rates of morbidity and mortality. Treating these infections poses numerous challenges, particularly when selecting appropriate empiric therapy for critically ill patients for whom the margin for error is low. Fortunately, the availability of new therapies has improved the treatment landscape, offering safer and more effective options. However, there remains a need to establish and implement optimal clinical and therapeutic approaches for managing these infections. Here, we review strategies for identifying patients at risk for MDR-GN infections, propose a framework for the choice of empiric and definitive treatment, and explore effective multidisciplinary approaches to managing patients in the hospital while ensuring a safe transition to outpatient settings.

Practical considerations for individualizing drug dosing in critically ill adults receiving renal replacement therapy

Critically ill patients with sepsis admitted to the intensive care unit (ICU) often present with or develop renal dysfunction requiring renal replacement therapy (RRT) in addition to antimicrobial therapy. While early and appropriate antimicrobials for sepsis have been associated with an increased probability of survival, adequate dosing is also required in these patients. Adequate dosing of antimicrobials refers to dosing strategies that achieve serum drug levels at the site of infection that are able to provide a microbiological and/or clinical response while avoiding toxicity from excessive antibiotic exposure. Therapeutic drug monitoring (TDM) is the recommended strategy to achieve this goal, however, TDM is not routinely available in all ICUs and for all antimicrobials. In the absence of TDM, clinicians are therefore required to make dosing decisions based on the clinical condition of the patient, the causative organism, the characteristics of RRT, and an understanding of the physicochemical properties of the antimicrobial. Pharmacokinetics (PK) of antimicrobials can be highly variable between critically ill patients and also within the same patient over the course of their ICU stay. The initiation of RRT, which can be in the form of intermittent hemodialysis, continuous, or prolonged intermittent therapy, further complicates the predictability of drug disposition. This variability highlights the need for individualized dosing. This review highlights the practical considerations for the clinician for antimicrobial dosing in critically ill patients receiving RRT.

Inoculum-Based Dosing: A Novel Concept for Combining Time with Concentration-Dependent Antibiotics to Optimize Clinical and Microbiological Outcomes in Severe Gram Negative Sepsis

Certain classes of antibiotics show "concentration dependent" antimicrobial activity; higher concentrations result in increased bacterial killing rates, in contrast to "time dependent antibiotics", which show antimicrobial activity that depends on the time that antibiotic concentrations remain above the MIC. Aminoglycosides and fluoroquinolones are still widely used concentration-dependent antibiotics. These antibiotics are not hydrolyzed by beta-lactamases and are less sensitive to the inoculum effect, which can be defined as an increased MIC for the antibiotic in the presence of a relatively higher bacterial load (inoculum). In addition, they possess a relatively long Post-Antibiotic Effect (PAE), which can be defined as the absence of bacterial growth when antibiotic concentrations fall below the MIC. These characteristics make them interesting complementary antibiotics in the management of Multi-Drug Resistant (MDR) bacteria and/or (neutropenic) patients with severe sepsis. Global surveillance studies have shown that up to 90% of MDR Gram-negative bacteria still remain susceptible to aminoglycosides, depending on the susceptibility breakpoint (e.g., CLSI or EUCAST) being applied. This percentage is notably lower for fluoroquinolones but depends on the region, type of organism, and mechanism of resistance involved. Daily (high-dose) dosing of aminoglycosides for less than one week has been associated with significantly less nephro/oto toxicity and improved target attainment. Furthermore, higher-than-conventional dosing of fluoroquinolones has been linked to improved clinical outcomes. Beta-lactam antibiotics are the recommended backbone of therapy for severe sepsis. Since these antibiotics are time-dependent, the addition of a second concentration-dependent antibiotic could serve to quickly lower the bacterial inoculum, create PAE, and reduce Penicillin-Binding Protein (PBP) expression. Inadequate antibiotic levels at the site of infection, especially in the presence of high inoculum infections, have been shown to be important risk factors for inadequate resistance suppression and therapeutic failure. Therefore, in the early phase of severe sepsis, effort should be made to optimize the dose and quickly lower the inoculum. In this article, the authors propose a novel concept of "Inoculum Based Dosing" in which the decision for antibiotic dosing regimens and/or combination therapy is not only based on the PK parameters of the patient, but also on the presumed inoculum size. Once the inoculum has been lowered, indirectly reflected by clinical improvement, treatment simplification should be considered to further treat the infection.

Extended Versus Intermittent Meropenem Infusion in the Treatment of Nosocomial Pneumonia: A Retrospective Single-Center Study

The efficacy of extended meropenem infusions in patients with nosocomial pneumonia is not well defined. Therefore, we compared the clinical outcomes of extended versus intermittent meropenem infusions in the treatment of nosocomial pneumonia. We performed a retrospective analysis of extended versus intermittent meropenem infusions in adult patients who had been treated for nosocomial pneumonia at a medical ICU between 1 May 2018 and 30 April 2020. The primary outcome was mortality at 14 days. Overall, 64 patients who underwent an extended infusion and 97 with an intermittent infusion were included in this study. At 14 days, 10 (15.6%) patients in the extended group and 22 (22.7%) in the intermittent group had died (adjusted hazard ratio (HR), 0.55; 95% confidence interval (CI): 0.23-1.31; p = 0.174). In the subgroup analysis, significant differences in mortality at day 14 were observed in patients following empirical treatment with meropenem (adjusted HR, 0.17; 95% CI: 0.03-0.96; p = 0.045) and in Gram-negative pathogens identified by blood or sputum cultures (adjusted HR, 0.01; 95% CI: 0.01-0.83; p = 0.033). Extended infusion of meropenem compared with intermittent infusion as a treatment option for nosocomial pneumonia may have a potential advantage in specific populations.

24/7 Therapeutic Drug Monitoring of Beta-Lactam Antibiotics with CLAM-2000

BACKGROUND

The aim of this study was to evaluate the CLAM-2000 automated preanalytical sample preparation module with integrated liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) as a method for 24/7 therapeutic drug monitoring (TDM) of beta-lactam antibiotics in routine clinical diagnostics.

METHODS

Method validation was performed using quality control samples. Method comparison was performed with routine samples from patients treated with beta-lactam antibiotics.

RESULTS

The determination of piperacillin, meropenem, ceftazidime, flucloxacillin, and cefotaxime was performed using D5-piperacillin and D6-meropenem as internal standards. The linearity of the method was within the therapeutic range of beta-lactam antibiotics. The imprecision and accuracy data obtained from quality control samples were within 15%, and the imprecision of patient samples on the instrument was less than the 5% coefficient of variation (CV). Internal standards stored in the instrument at 9 °C for at least one week were stable, which facilitated reagent use and storage.

CONCLUSION

The CLAM-2000 (Shimadzu, Kyoto, Japan) provides reproducible results as an established routine instrument and is a useful tool for 24/7 TDM of beta-lactam antibiotics in routine clinical diagnostics.

Meropenem PK/PD Variability and Renal Function: "We Go Together"

BACKGROUND

Meropenem is a carbapenem antibiotic widely employed for serious bacterial infections. Therapeutic drug monitoring (TDM) is a strategy to optimize dosing, especially in critically ill patients. This study aims to show how TDM influences the management of meropenem in a real-life setting, not limited to intensive care units.

METHODS

From December 2021 to February 2022, we retrospectively analyzed 195 meropenem serum concentrations (Css). We characterized patients according to meropenem exposure, focusing on the renal function impact.

RESULTS

A total of 36% (n = 51) of the overall observed patients (n = 144) were in the therapeutic range (8-16 mg/L), whereas 64% (n = 93) required a meropenem dose modification (37 patients (26%) underexposed; 53 (38%) overexposed). We found a strong relationship between renal function and meropenem concentrations (correlation coefficient = -0.7; p-value < 0.001). We observed different dose-normalized meropenem exposure (Css/D) among renal-impaired (severe and moderate), normal, and hyperfiltrating patients, with a median (interquartile range) of 13.1 (10.9-20.2), 7.9 (6.1-9.5), 3.8 (2.6-6.0), and 2.4 (1.6-2.7), respectively (p-value < 0.001).

CONCLUSIONS

Meropenem TDM in clinical practice allows modification of dosing in patients inadequately exposed to meropenem to maximize antibiotic efficacy and minimize the risk of antibiotic resistance, especially in renal alterations despite standard dose adaptations.

β-Lactam Pharmacokinetic/Pharmacodynamic Target Attainment in Intensive Care Unit Patients: A Prospective, Observational, Cohort Study

BACKGROUND

The aims of this study were to describe pharmacokinetic/pharmacodynamic target attainment in intensive care unit (ICU) patients treated with continuously infused ß-lactam antibiotics, their associated covariates, and the impact of dosage adjustment.

METHODS

This prospective, observational, cohort study was performed in three ICUs. Four ß-lactams were continuously infused, and therapeutic drug monitoring (TDM) was performed at days 1, 4, and 7. The primary pharmacokinetic/pharmacodynamic target was an unbound ß-lactam plasma concentration four times above the bacteria's minimal inhibitory concentration during the whole dosing interval. The demographic and clinical covariates associated with target attainment were evaluated.

RESULTS

A total of 170 patients were included (426 blood samples). The percentages of empirical ß-lactam underdosing at D1 were 66% for cefepime, 43% for cefotaxime, 47% for ceftazidime, and 14% for meropenem. Indexed creatinine clearance was independently associated with treatment underdose if increased (adjusted odds ratio per unit, 1.01; 95% CI, 1.00 to 1.01; p = 0.014) or overdose if decreased (adjusted odds ratio per unit, 0.95; 95% CI, 0.94 to 0.97; p < 0.001). Pharmacokinetic/pharmacodynamic target attainment was significantly increased after ß-lactam dosage adjustment between day 1 and day 4 vs. no adjustment (53.1% vs. 26.2%; p = 0.018).

CONCLUSIONS

This study increases our knowledge on the optimization of ß-lactam therapy in ICU patients. A large inter- and intra-patient variability in plasmatic concentrations was observed, leading to inadequate exposure. A combined indexed creatinine clearance and TDM approach enables adequate dosing for better pharmacokinetic/pharmacodynamic target attainment.

Pharmacokinetics of ampicillin during venovenous extracorporeal membrane oxygenation: A case report

The presence of extracorporeal membrane oxygenation (ECMO) in addition to underlying critical illness can affect the pharmacokinetics and pharmacodynamics of drugs that are often required to treat this patient population. While ampicillin is the preferred agent for the treatment of susceptible Enterococcus faecalis infections, there are no in vivo pharmacokinetic studies regarding ampicillin dosing in patients receiving ECMO. This case report consists of two patients on venovenous ECMO with E. faecalis bloodstream infections in which ampicillin serum concentrations were measured. Pharmacokinetic parameters were calculated using a one compartment open model. Ampicillin trough levels were 5.87 and 39.2 mg/L for patients A and B, respectively. Based on these results, ampicillin concentrations were found to be above the minimum inhibitory concentration (MIC) for 100% of the dosing interval. The findings of this case report demonstrate that therapeutic concentrations of ampicillin can be obtained in patients on ECMO and therapeutic drug monitoring can be utilized to ensure adequate serum concentrations are achieved.

Why is the Implementation of Beta-Lactam Therapeutic Drug Monitoring for the Critically Ill Falling Short? A Multicenter Mixed-Methods Study

BACKGROUND

Beta-lactam therapeutic drug monitoring (BL TDM; drug level testing) can facilitate improved outcomes in critically ill patients. However, only 10%-20% of hospitals have implemented BL TDM. This study aimed to characterize provider perceptions and key considerations for successfully implementing BL TDM.

METHODS

This was a sequential mixed-methods study from 2020 to 2021 of diverse stakeholders at 3 academic medical centers with varying degrees of BL TDM implementation (not implemented, partially implemented, and fully implemented). Stakeholders were surveyed, and a proportion of participants completed semistructured interviews. Themes were identified, and findings were contextualized with implementation science frameworks.

RESULTS

Most of the 138 survey respondents perceived that BL TDM was relevant to their practice and improved medication effectiveness and safety. Integrated with interview data from 30 individuals, 2 implementation themes were identified: individual internalization and organizational features. Individuals needed to internalize, make sense of, and agree to BL TDM implementation, which was positively influenced by repeated exposure to evidence and expertise. The process of internalization appeared more complex with BL TDM than with other antibiotics (ie, vancomycin). Organizational considerations relevant to BL TDM implementation (eg, infrastructure, personnel) were similar to those identified in other TDM settings.

CONCLUSIONS

Broad enthusiasm for BL TDM among participants was found. Prior literature suggested that assay availability was the primary barrier to implementation; however, the data revealed many more individual and organizational attributes, which impacted the BL TDM implementation. Internalization should particularly be focused on to improve the adoption of this evidence-based practice.

Optimizing the Use of Beta-Lactam Antibiotics in Clinical Practice: A Test of Time

Despite their limitations, the pharmacokinetics (PK) and pharmacodynamics (PD) indices form the basis for our current understanding regarding antibiotic development, selection, and dose optimization. Application of PK-PD in medicine has been associated with better clinical outcome, suppression of resistance, and optimization of antibiotic consumption. Beta-lactam antibiotics remain the cornerstone for empirical and directed therapy in many patients. The percentage of time of the dosing interval that the free (unbound) drug concentration remains above the minimal inhibitory concentration (MIC) (%fT > MIC) has been considered the PK-PD index that best predicts the relationship between antibiotic exposure and killing for the beta-lactam antibiotics. Time dependence of beta-lactam antibiotics has its origin in the acylation process of the serine active site of penicillin-binding proteins, which subsequently results in bacteriostatic and bactericidal effects during the dosing interval. To enhance the likelihood of target attainment, higher doses, and prolonged infusion strategies, with/or without loading doses, have been applied to compensate for subtherapeutic levels of antibiotics related to PK-PD changes, especially in the early phase of severe sepsis. To minimize resistance and maximize clinical outcome, empirical therapy with a meropenem loading dose followed by high-dose-prolonged infusion should be considered in patients with high inoculum infections presenting as severe (Gram negative) sepsis. Subsequent de-escalation and dosing of beta-lactam antibiotics should be considered as an individualized dynamic process that requires dose adjustments throughout the time course of the disease process mediated by clinical parameters that indirectly assess PK-PD alterations.

Beta-Lactam Dose Optimisation in the Intensive Care Unit: Targets, Therapeutic Drug Monitoring and Toxicity

Beta-lactams are an important family of antibiotics used to treat infections and are commonly used in critically ill patients. Optimal use of these drugs in the intensive care unit (ICU) is important because of the serious complications from sepsis. Target beta-lactam antibiotic exposures may be chosen using fundamental principles of beta-lactam activity derived from pre-clinical and clinical studies, although the debate regarding optimal beta-lactam exposure targets is ongoing. Attainment of target exposures in the ICU requires overcoming significant pharmacokinetic (PK) and pharmacodynamic (PD) challenges. For beta-lactam drugs, the use of therapeutic drug monitoring (TDM) to confirm if the desired exposure targets are achieved has shown promise, but further data are required to determine if improvement in infection-related outcomes can be achieved. Additionally, beta-lactam TDM may be useful where a relationship exists between supratherapeutic antibiotic exposure and drug adverse effects. An ideal beta-lactam TDM service should endeavor to efficiently sample and report results in identified at-risk patients in a timely manner. Consensus beta-lactam PK/PD targets associated with optimal patient outcomes are lacking and should be a focus for future research.

Update on Therapeutic Drug Monitoring of Beta-Lactam Antibiotics in Critically Ill Patients—A Narrative Review

Beta-lactam antibiotics remain one of the most preferred groups of antibiotics in critical care due to their excellent safety profiles and their activity against a wide spectrum of pathogens. The cornerstone of appropriate therapy with beta-lactams is to achieve an adequate plasmatic concentration of a given antibiotic, which is derived primarily from the minimum inhibitory concentration (MIC) of the specific pathogen. In a critically ill patient, the plasmatic levels of drugs could be affected by many significant changes in the patient’s physiology, such as hypoalbuminemia, endothelial dysfunction with the leakage of intravascular fluid into interstitial space and acute kidney injury. Predicting antibiotic concentration from models based on non-critically ill populations may be misleading. Therapeutic drug monitoring (TDM) has been shown to be effective in achieving adequate concentrations of many drugs, including beta-lactam antibiotics. Reliable methods, such as high-performance liquid chromatography, provide the accurate testing of a wide range of beta-lactam antibiotics. Long turnaround times remain the main drawback limiting their widespread use, although progress has been made recently in the implementation of different novel methods of antibiotic testing. However, whether the TDM approach can effectively improve clinically relevant patient outcomes must be proved in future clinical trials.

Evaluation of continuous ampicillin/sulbactam infusion in critically ill patients

Continuous infusion (CI) of beta-lactam-antibiotics may improve pharmacodynamics in critically ill patients, but resulting concentrations have not been studied. Therapeutic drug monitoring is increasingly used to ensure antibiotic concentration. The aim of this study is to evaluate therapeutic ampicillin/sulbactam concentrations of a continuous infusion regimen.

METHODS

Medical records of all patients admitted to ICU between January 2019 and December 2020 were retrospectively reviewed. Each patient received a 2/1 g ampicillin/sulbactam loading dose, followed by a continuous infusion of 8/4 g per 24 h. Ampicillin serum concentrations were measured. Main outcomes were reaching of plasma concentrations breakpoint defined by minimum inhibitory concentration (MIC at 8 mg/l) and 4-fold MIC (MIC at 32 mg/l) during steady state of CI.

RESULTS

In 50 patients a total of 60 concentration measurements were performed. The first concentration was measured after a median of 29 h (IQR 21-61 h). Mean ampicillin concentration was 62.6 ± 39.1 mg/l. Furthermore, serum concentrations exceeded the defined MIC breakpoint in all measurements (100 %) and were above the 4-fold MIC in 43 analyses (71.1 %). However, patients suffering from acute kidney injury exhibited significant higher serum concentrations (81.1 ± 37.7 mg/l vs. 38.2 ± 24.8 mg/l; p < 0.001). Also, there was a negative correlation between ampicillin serum concentrations and GFR (r = -0.659; p < 0.001).

CONCLUSION

The described dosing regimen for ampicillin/sulbactam is safe with respect to the defined MIC breakpoints for ampicillin, and continuous subtherapeutic concentration is unlikely. However, with impaired renal function drug accumulation occurs, and with increased renal clearance, drug levels can be below the 4-fold MIC breakpoint.

Beta-lactam target attainment and associated outcomes in patients with bloodstream infections

OBJECTIVES

To evaluate the association between early and cumulative beta-lactam pharmacokinetic/pharmacodynamic (PK/PD) parameters and therapy outcomes in bloodstream infection (BSI).

METHODS

Adult patients who received cefepime, meropenem, or piperacillin/tazobactam for BSI and had concentrations measured were included. Beta-lactam exposure was generated and the time that free concentration remained above the minimum inhibitory concentration (fT_>MIC) and four multiples of MIC (fT_>4 × MIC) were calculated for times 0-24 h and 0-7 days of therapy. Multiple regression analysis was performed to evaluate the impact of PK/PD on microbiological and clinical outcomes.

RESULTS

A total of 204 patients and 213 BSI episodes were included. The mean age was 58 years and weight 83 kg. Age, Sequential Organ Failure Assessment (SOFA) score, haemodialysis, Pitt bacteraemia score, and hours of empiric antibiotic therapy were significantly associated with certain outcomes and retained in the final model. In multiple regression analysis, fT_>4 × MIC at 0-24 h and 0-7 days was a significant predictor of negative blood culture on day 7 (P=0.0161 and 0.0068, respectively). In the time-to-event analysis, patients who achieved 100% fT_>4 × MIC at 0-24 h and 0-7 days had a shorter time to negative blood culture compared with those who did not (log-rank P=0.0004 and 0.0014, respectively). No significant associations were identified between PK/PD parameters and other outcomes, including improvement in symptoms at day 7 and 30-day mortality.

CONCLUSION

Early and cumulative achievement of fT_>4 × MIC was a significant predictor of microbiological outcome in patients with BSI.

Beta-lactam exposure and safety in intermittent or continuous infusion in critically ill children: an observational monocenter study

The aim of this study was to assess the pharmacokinetic (PK) exposure and clinical toxicity for three beta-lactams: cefotaxime, piperacillin/tazobactam, and meropenem, depending on two lengths of infusion: continuous and intermittent, in critically ill children. This single center observational prospective study was conducted in a pediatric intensive care unit. All hospitalized children who had one measured plasma concentration of the investigated antibiotics were included. Plasma antibiotic concentrations were interpreted by a pharmacologist, using a Bayesian approach based on previously published population pharmacokinetic models in critically ill children. Exposure was considered optimal, low, or high according to the PK target 100% fT_{> 4 × MIC} and a trough concentration below the toxic concentration (50 mg.L^-1 for cefotaxime, 150 mg.L^-1 for piperacillin, and 44 mg.L^-1 for meropenem). Between May 2019 and January 2020, 80 patients were included and received 106 antibiotic courses: 74 (70%) were administered in intermittent infusion (II) and 32 (30%) in continuous infusion (CI). Compared to II, CI provided more optimal PK exposure (n = 22/32, 69% for CI versus n = 35/74, 47% for II, OR 1.2, 95%CI 1.01-1.5, p = 0.04), less underexposure (n = 4/32, 13% for CI versus n = 36/74, 49% for II, OR 0.7, 95%CI 0.6-0.84, p < 0.001), and more overexposure (n = 6/32, 19% for CI versus n = 3/74, 4% for II, OR 1.2, 95%CI 1.03-1.3, p = 0.01). Five adverse events have been reported during the study period, although none has been attributed to beta-lactam treatment.

CONCLUSION

CI provided a higher probability to attain an optimal PK target compared to II, but also a higher risk for overexposure. Regular therapeutic drug monitoring is recommended in critically ill children receiving beta-lactams, regardless of the length of infusion.

WHAT IS KNOWN

• Since beta-lactams are time-dependent antibiotics, the probability to attain the pharmacokinetic target is higher with continuous infusion compared to that with intermittent infusion. • In daily practice, continuous or extended infusions are rarely used despite recent guidelines, and toxicity is hardly reported.

WHAT IS NEW

• Continuous infusion provided a higher probability to attain an optimal pharmacokinetic target compared to intermittent infusion, but also a higher risk of overexposure. • Regular therapeutic drug monitoring is recommended in critically ill children receiving beta-lactams, regardless of the length of infusion.

Pharmacokinetic parameters over time during sepsis and the association of target attainment and outcomes in critically ill children and young adults receiving ceftriaxone

INTRODUCTION

Early sepsis results in pharmacokinetic (PK) changes due to physiologic alterations. PK changes can lead to suboptimal drug target attainment, risking inadequate coverage from antibiotics like ceftriaxone. Little is known about how ceftriaxone PK and target attainment quantitatively change over time in patients with sepsis or the association between target attainment and outcomes in critically ill children and young adults.

METHODS

A retrospective analysis of a prospective study was conducted in a single-center pediatric intensive care unit. Septic patients given at least one ceftriaxone dose (commonly as 50 mg/kg every 12 h) and who had blood obtained in both the first 48 h of therapy (early) and afterwards (late) were included. Normalized clearance and central volume were estimated and compared in both sepsis phases. We evaluated target attainment, defined as concentrations above 1× or 4× the minimum inhibitory concentration (MIC) for 100% of dosing intervals, and investigated the association between target attainment and clinical outcomes.

RESULTS

Fifty-five septic patients (median age: 7.5 years) were included. Normalized clearance and central volume were similar in both phases (6.18 ± 1.48 L/h/70 kg early vs. 6.10 ± 1.61 L/h/70 kg late, p = 0.60; 26.6 [IQR 22.3, 31.3] L/70 kg early vs. 24.5 [IQR 22.0, 29.4] L/70 kg late, p = 0.18). Individual percent differences in normalized clearance and central volume between sepsis phases ranged from -39% to 276% and -51% to 212% (reference, late sepsis), respectively. Fewer patients attained the 1× MIC target in late sepsis (82% late vs. 96% early, p = 0.013), which was associated with transition to once daily dosing, typically done due to transfer from the pediatric intensive care unit (PICU) to a lower acuity unit. Failure to attain either target in late sepsis was associated with antibiotic broadening.

CONCLUSION

Ceftriaxone PK parameters were similar between early and late sepsis, but there were large individual differences. Fewer patients attained MIC targets in late sepsis and all who did not attain the less stringent target received once daily dosing during this period. The failure to attain targets in late sepsis was associated with antibiotic broadening and could be an area for antibiotic stewardship intervention.

Continuous Infusion of High Doses of Cefepime in Intensive Care Unit: Assessment of Steady-State Plasma Level and Incidence on Neurotoxicity

Continuous infusion (CI) with high doses of cefepime is recommended in the empirical antimicrobial regimen of critically ill patients with suspected Gram-negative sepsis. This study aimed to determine factors associated with cefepime overdosing and the incidence of cefepime-induced neurotoxicity (CIN) in these patients. We performed a retrospective study including all patients receiving cefepime treatment between January 2019 and May 2022. The plasma level of cefepime defining overdosing was over 35 mg/L. Neurotoxicity was defined according to strict criteria and correlated with concomitant steady-state concentration of cefepime. Seventy-eight courses of cefepime treatment were analyzed. The mean cefepime plasma level at steady state was 59.8 ± 29.3 mg/L, and overdosing occurred in 80% of patients. Renal failure and a daily dose > 5 g were independently associated with overdosing. CIN was present in 30% of patients. In multivariate analysis, factors associated with CIN were chronic renal failure and a cefepime plasma concentration ≥ 60 mg/L. CIN was not associated with mortality. Overdosing is frequent in patients receiving high doses of cefepime by CI. Steady-state levels are higher than targeted therapeutic pharmacokinetic/pharmacodynamic objectives. The risk of CIN is important when the plasma concentration is ≥60 mg/L.

Low attainment to PK/PD-targets for β-lactams in a multi-center study on the first 72 h of treatment in ICU patients

Severe infections are life-threatening conditions commonly seen in the intensive care units (ICUs). Antibiotic treatment with adequate concentrations is of great importance during the first days when the bacterial load is the highest. Therapeutic drug monitoring (TDM) of β-lactam antibiotics has been suggested to monitor target attainment and to improve the outcome. This prospective multi-center study in seven ICUs in Sweden investigated pharmacokinetic/pharmacodynamic-target (PK/PD-target) attainment for cefotaxime, piperacillin-tazobactam and meropenem, commonly used β-lactams in Sweden. A mid-dose and trough antibiotic concentration blood sample were taken from patients with severe infection daily during the first 72 h of treatment. Antibiotic plasma concentrations were analysed by liquid chromatography-mass spectrometry (LC-MS). Antibiotic concentrations 100% time above MIC (minimal inhibitory concentration), (100% T > MIC) and four times above MIC 50% of the time (50% T > 4xMIC) were used as PK/PD-targets. We included 138 patients with the median age of 67 years and the median Simplified Acute Physiology Score 3 (SAPS3) of 59. Forty-five percent of the study-population failed to reach 100% T > MIC during the first day of treatment. The results were similar the following two days. There was a three-fold risk of not meeting the PK/PD target if the patient was treated with cefotaxime. For the cefotaxime treated patients 8 out of 55 (15%) had at least one end-dose concentrations below the level of detection during the study. Low age, low illness severity, low plasma creatinine, lower respiratory tract infection and cefotaxime treatment were risk factors for not reaching 100% T > MIC. In Swedish ICU-patients treated with β-lactam antibiotics, a high proportion of patients did not reach the PK/PD target. TDM could identify patients that need individual higher dosing regimens already on the first day of treatment. Further studies on optimal empirical start dosing of β-lactams, especially for cefotaxime, in the ICU are needed.Trial registration: The protocol was retrospectively registered 100216 (ACTRN12616000167460).

β-Lactam Dosing in Critical Patients: A Narrative Review of Optimal Efficacy and the Prevention of Resistance and Toxicity

Antimicrobial prescription in critically ill patients represents a complex challenge due to the difficult balance between infection treatment and toxicity prevention. Underexposure to antibiotics and therapeutic failure or, conversely, drug overexposure and toxicity may both contribute to a worse prognosis. Moreover, changes in organ perfusion and dysfunction often lead to unpredictable pharmacokinetics. In critically ill patients, interindividual and intraindividual real-time β-lactam antibiotic dose adjustments according to the patient's condition are critical. The continuous infusion of β-lactams and the therapeutic monitoring of their concentration have both been proposed to improve their efficacy, but strong data to support their use are still lacking. The knowledge of the pharmacokinetic/pharmacodynamic targets is poor and is mostly based on observational data. In patients with renal or hepatic failure, selecting the right dose is even more tricky due to changes in drug clearance, distribution, and the use of extracorporeal circuits. Intermittent usage may further increase the dosing conundrum. Recent data have emerged linking overexposure to β-lactams to central nervous system toxicity, mitochondrial recovery delay, and microbiome changes. In addition, it is well recognized that β-lactam exposure facilitates resistance selection and that correct dosing can help to overcome it. In this review, we discuss recent data regarding real-time β-lactam antibiotic dose adjustment, options in special populations, and the impacts on mitochondria and the microbiome.

When and How to Use MIC in Clinical Practice?

Bacterial resistance to antibiotics continues to be a global public health problem. The choice of the most effective antibiotic and the use of an adapted dose in the initial phase of the infection are essential to limit the emergence of resistance. This will depend on (i) the isolated bacteria and its resistance profile, (ii) the pharmacodynamic (PD) profile of the antibiotic used and its level of toxicity, (iii) the site of infection, and (iv) the pharmacokinetic (PK) profile of the patient. In order to take account of both parameters to optimize the administered treatment, a minimal inhibitory concentration (MIC) determination associated with therapeutic drug monitoring (TDM) and their combined interpretation are required. The objective of this narrative review is thus to suggest microbiological, pharmacological, and/or clinical situations for which this approach could be useful. Regarding the microbiological aspect, such as the detection of antibiotic resistance and its level, the preservation of broad-spectrum β-lactams is particularly discussed. PK-PD profiles are relevant for difficult-to-reach infections and specific populations such as intensive care patients, cystic fibrosis patients, obese, or elderly patients. Finally, MIC and TDM are tools available to clinicians, who should not hesitate to use them to manage their patients.

β-lactam precision dosing in critically ill children: Current state and knowledge gaps

There has been emerging interest in implementing therapeutic drug monitoring and model-informed precision dosing of β-lactam antibiotics in critically ill patients, including children. Despite a position paper endorsed by multiple international societies that support these efforts in critically ill adults, implementation of β-lactam precision dosing has not been widely adopted. In this review, we highlight what is known about β-lactam antibiotic pharmacokinetics and pharmacodynamics in critically ill children. We also define the knowledge gaps that present barriers to acceptance and implementation of precision dosing of β-lactam antibiotics in critically ill children: a lack of consensus on which subpopulations would benefit most from precision dosing and the uncertainty of how precision dosing changes outcomes. We conclude with opportunities for further research to close these knowledge gaps.

Empirical Antibiotic Therapy for Gram-Negative Bacilli Ventilator-Associated Pneumonia: Observational Study and Pharmacodynamic Assessment

Background: Strong evidence suggests a correlation between pharmacodynamics (PD) index and antibiotic efficacy while dose adjustment should be considered in critically ill patients due to modified pharmacokinetic (PK) parameters and/or higher minimum inhibitory concentrations (MICs). This study aimed to assess pharmacodynamic (PD) target attainment considering both antibiotics serum concentrations and measured MICs in these patients. Method: A multicentric prospective open-label trial conducted in 11 French ICUs involved patients with Gram-negative bacilli (GNB) ventilator-associated pneumonia (VAP) confirmed by quantitative cultures. Results: We included 117 patients. Causative GNBs were P. aeruginosa (40%), Enterobacter spp. (23%), E. coli (20%), and Klebsiella spp. (16%). Hence, 117 (100%) patients received β-lactams, 65 (58%) aminoglycosides, and two (1.5%) fluoroquinolones. For β-lactams, 83% of the patients achieved a Cmin/MIC > 1 and 70% had a Cmin/MIC > 4. In the case of high creatinine clearance (CrCL > 100 mL/min/1.73 m2), 70.4% of the patients achieved a Cmin/MIC ratio > 1 versus 91% otherwise (p = 0.041), and 52% achieved a Cmin/MIC ratio > 4 versus 81% (p = 0.018). For aminoglycosides, 94% of the patients had a Cmax/MIC ratio > 8. Neither β-lactams nor aminoglycosides PK/PD parameters were associated clinical outcomes, but our data suggest a correlation between β-lactams Cmin/MIC and microbiological success. Conclusion: In our ICU patients treated for GNB VAP, using recommended antibiotic dosage led in most cases to PK/PD targets attainment for aminoglycosides and β-lactams. High creatinine clearance should encourage clinicians to focus on PK/PD issues.

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.

The 2021 Dutch Working Party on Antibiotic Policy (SWAB) guidelines for empirical antibacterial therapy of sepsis in adults

BACKGROUND

The Dutch Working Party on Antibiotic Policy (SWAB) in collaboration with relevant professional societies, has updated their evidence-based guidelines on empiric antibacterial therapy of sepsis in adults.

METHODS

Our multidisciplinary guideline committee generated ten population, intervention, comparison, and outcome (PICO) questions relevant for adult patients with sepsis. For each question, a literature search was performed to obtain the best available evidence and assessed using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system. The quality of evidence for clinically relevant outcomes was graded from high to very low. In structured consensus meetings, the committee formulated recommendations as strong or weak. When evidence could not be obtained, recommendations were provided based on expert opinion and experience (good practice statements).

RESULTS

Fifty-five recommendations on the antibacterial therapy of sepsis were generated. Recommendations on empiric antibacterial therapy choices were differentiated for sepsis according to the source of infection, the potential causative pathogen and its resistance pattern. One important revision was the distinction between low, increased and high risk of infection with Enterobacterales resistant to third generation cephalosporins (3GRC-E) to guide the choice of empirical therapy. Other new topics included empirical antibacterial therapy in patients with a reported penicillin allergy and the role of pharmacokinetics and pharmacodynamics to guide dosing in sepsis. We also established recommendations on timing and duration of antibacterial treatment.

CONCLUSIONS

Our multidisciplinary committee formulated evidence-based recommendations for the empiric antibacterial therapy of adults with sepsis in The Netherlands.

Using Machine Learning To Define the Impact of Beta-Lactam Early and Cumulative Target Attainment on Outcomes in Intensive Care Unit Patients with Hospital-Acquired and Ventilator-Associated Pneumonia

Hospital-acquired pneumonia (HAP) and ventilator-associated pneumonia (VAP) are the most common intensive care unit (ICU) infections. We aimed to evaluate the association of early and cumulative beta-lactam pharmacokinetic/pharmacodynamic (PK/PD) parameters with therapy outcomes in pneumonia. Adult ICU patients who received cefepime, meropenem, or piperacillin-tazobactam for HAP or VAP and had its concentration measured were included. Beta-lactam exposure was generated for every patient for the entire duration of therapy, and the time free concentration remained above the MIC (fT_>MIC) and the time free concentration remained above four multiples of the MIC (fT_>4×MIC) were calculated for time frames of 0 to 24 h, 0 to 10 days, and day 0 to end of therapy. Regression analyses and machine learning were performed to evaluate the impact of PK/PD on therapy outcomes. A total of 735 patients and 840 HAP/VAP episodes (47% HAP) were included. The mean age was 56 years, and the mean weight was 80 kg. Sequential organ failure assessment (SOFA), hemodialysis, age, and weight were significantly associated with the clinical outcomes and kept in the final model. In the full cohort including all pneumonia episodes, PK/PD parameters at different time windows were associated with a favorable composite outcome, clinical cure, and mechanical ventilation (MV)-free days. In patients who had positive cultures and reported MICs, almost all PK/PD parameters were significant predictors of therapy outcomes. In the machine learning analysis, PK/PD parameters ranked high and were the primary overall predictors of clinical cure. Early target attainment and cumulative target attainment have a great impact on pneumonia outcomes. Beta-lactam exposure should be optimized early and maintained through therapy duration.

Towards Improved Management of Tuberculous Bloodstream Infections: Pharmacokinetic Considerations with Suggestions for Better Treatment Outcomes

Mycobacterium tuberculosis is the leading cause of sepsis among HIV-infected adults, yet effective treatment remains a challenge. Efficacy of antituberculous drugs is optimized by high Area Under Curve to Minimum Inhibitory Concentration (AUC/MIC) ratios, suggesting that both the drug concentration at the disease site and time above MIC are critical to treatment outcomes. We elaborate on sepsis pathophysiology and show how it adversely affects antituberculous drug kinetics. Expanding distribution volumes secondary to an increased vascular permeability prevents the attainment of target Cmax concentrations for nearly all drugs. Furthermore, sepsis-induced metabolic acidosis promotes protonation, which increases renal clearance of basic drugs such as isoniazid and ethambutol, and hence AUCs are substantially reduced. Compared with the treatment of non-sepsis TB disease, these distorted kinetics underlie the poor treatment outcomes observed with bloodstream infections. In addition to aggressive hemodynamic management, an increase in both the dose and frequency of drug administration are warranted, at least in the early phase of treatment.

Why We May Need Higher Doses of Beta-Lactam Antibiotics: Introducing the 'Maximum Tolerable Dose'

The surge in antimicrobial resistance and the limited availability of new antimicrobial drugs has fueled the interest in optimizing antibiotic dosing. An ideal dosing regimen leads to maximal bacterial cell kill, whilst minimizing the risk of toxicity or antimicrobial resistance. For beta-lactam antibiotics specifically, PK/PD-based considerations have led to the widespread adoption of prolonged infusion. The rationale behind prolonged infusion is increasing the percentage of time the beta-lactam antibiotic concentration remains above the minimal inhibitory concentration (%fT>MIC). The ultimate goal of prolonged infusion of beta-lactam antibiotics is to improve the outcome of infectious diseases. However, merely increasing target attainment (or the %fT>MIC) is unlikely to lead to improved clinical outcome for several reasons. First, the PK/PD index and target are dynamic entities. Changing the PK (as is the case if prolonged instead of intermittent infusion is used) will result in different PK/PD targets and even PK/PD indices necessary to obtain the same level of bacterial cell kill. Second, the minimal inhibitory concentration is not a good denominator to describe either the emergence of resistance or toxicity. Therefore, we believe a different approach to antibiotic dosing is necessary. In this perspective, we introduce the concept of the maximum tolerable dose (MTD). This MTD is the highest dose of an antimicrobial drug deemed safe for the patient. The goal of the MTD is to maximize bacterial cell kill and minimize the risk of antimicrobial resistance and toxicity. Unfortunately, data about what beta-lactam antibiotic levels are associated with toxicity and how beta-lactam antibiotic toxicity should be measured are limited. This perspective is, therefore, a plea to invest in research aimed at deciphering the dose−response relationship between beta-lactam antibiotic drug concentrations and toxicity. In this regard, we provide a theoretical approach of how increasing uremic toxin concentrations could be used as a quantifiable marker of beta-lactam antibiotic toxicity.

Clinical and microbiological evaluation of temocillin for bloodstream infections with Enterobacterales: a Belgian single-centre retrospective study

Background

Expanding the use of temocillin could be an important weapon in the fight against antimicrobial resistance. However, EUCAST defined clinical breakpoints for a limited number of species and only for urinary tract infections (UTI), including urosepsis but excluding severe sepsis and septic shock. Moreover, a dosage of 2 g q8h is advised in most cases.

Objectives

Evaluation of temocillin use for the treatment of bacteraemia, correlating clinical and microbiological outcomes with infection site, infection severity, temocillin dosage, Enterobacterales species and MIC.

Patients and methods

All adult patients with blood cultures positive for temocillin-susceptible Enterobacterales and treated with temocillin for ≥72 h from June 2018 until June 2021 were considered for inclusion. The primary outcome was clinical success, defined as resolution of infection signs, no relapse of the same infection and no antibiotic switch due to insufficient clinical improvement. The secondary outcome was microbiological success.

Results

In total, 182 episodes were included [140 UTI versus 42 non-UTI, 171 Escherichia coli, Klebsiella species (except Klebsiella aerogenes) and Proteus mirabilis (EKPs) versus 11 non-EKPs]. Clinical and microbiological failure were low (8% and 3%, respectively). No difference in outcome was observed for dosages of 2 g q12h versus 2 g q8h, either for EKP versus non-EKP isolates or MIC values ≤8 versus 16 mg/L. Considering only bacteraemia episodes of UTI origin, using the 16 mg/L breakpoint, there was no difference in success rate between regimens of 2 g q12h and 2 g q8h.

Conclusions

Temocillin 2 g q12h can be successfully used for the treatment of systemic UTI. Prospective studies are needed to assess outcomes and evaluate non-inferiority compared with other broad-spectrum antibiotics in non-UTI infections, including bacteraemia.

Clinical Pharmacokinetics and Pharmacodynamics of Cefepime

Cefepime is a broad-spectrum fourth-generation cephalosporin with activity against Gram-positive and Gram-negative pathogens. It is generally administered as an infusion over 30-60 min or as a prolonged infusion with infusion times from 3 h to continuous administration. Cefepime is widely distributed in biological fluids and tissues with an average volume of distribution of ~ 0.2 L/kg in healthy adults with normal renal function. Protein binding is relatively low (20%), and elimination is mainly renal. About 85% of the dose is excreted unchanged in the urine, with an elimination half-life of 2-2.3 h. The pharmacokinetics of cefepime is altered under certain pathophysiological conditions, resulting in high inter-individual variability in cefepime volume of distribution and clearance, which poses challenges for population dosing approaches. Consequently, therapeutic drug monitoring of cefepime may be beneficial in certain patients including those who are critically ill, have life-threatening infections, or are infected with more resistant pathogens. Cefepime is generally safe and efficacious, with a goal exposure target of 70% time of the free drug concentration over the minimum inhibitory concentration for clinical efficacy. In recent years, reports of neurotoxicity have increased, specifically in patients with impaired renal function. This review summarizes the pharmacokinetics, pharmacodynamics, and toxicodynamics of cefepime contemporarily in the setting of increasing cefepime exposures. We explore the potential benefits of extended or continuous infusions and therapeutic drug monitoring in special populations.

High-throughput analysis for the simultaneous quantification of nine beta-lactam antibiotics in human plasma by UPC2-MS/MS: Method development, validation, and clinical application

Quantification of beta-lactam antibiotics can be performed by using liquid chromatography in combination with tandem mass spectrometry (MS/MS) or ultraviolet (UV) detection. Since beta-lactam antibiotics are known as highly polar analytes, using standard reversed phase chromatography will result in very early elution, which is often not desirable. Some retention is preferred to reduce matrix effects, because a high amount of non-retained molecular matrix species elute early from the column. For highly polar analytes, ultra-performance convergence chromatography (UPC²) may be a suitable alternative. This method is based on supercritical fluid chromatography. To our knowledge, we developed the first UPC²-MS/MS method for the determination of amoxicillin, benzylpenicillin, flucloxacillin, piperacillin, cefotaxime, cefuroxime, ceftazidime, imipenem, meropenem, and the free fraction of cefuroxime and flucloxacillin in human plasma. The method was validated according to the Food and Drug Administration guidelines. The method was found linear (r² >0.990) for all analytes. The inaccuracies and imprecisions were < 15% for all analytes. The matrix effect and recovery were nearly all consistent with coefficient of variation of less than 15% and no significant carryover effect was observed. Furthermore, this method was found to be suitable for daily routine analysis in hospital settings, requiring only 50 µL of plasma. This novel, sensitive, and specific UPC²-MS/MS method demonstrated its value in the analysis of a more than 800 human plasma samples in a clinical trial using simple and fast sample preparation and short analysis run time of only 5 min.

Cefepime population pharmacokinetics and dosing regimen optimization in critically ill children with different renal function

OBJECTIVE

Cefepime is commonly used in pediatric intensive care units (PICUs), where unpredictable variations in the patients' pharmacokinetic (PK) variables may require drug dose adjustments. The objectives of the present study were to build a population PK model for cefepime in critically ill children and to optimize individual initial dosing regimens.

METHODS

Children (aged from 1 month to 18 years; bodyweight >3 kg) receiving cefepime were included. Cefepime total plasma concentrations were measured using high performance liquid chromatography. Data were modelled using non-linear, mixed-effect modeling software, and Monte Carlo simulations were performed with a PK target of 100% fT _{> MIC}.

RESULTS

Fifty-nine patients (median (range) age: 13.5 months (1.1 month-17.6 years)) and 129 cefepime concentration measurements were included. The cefepime concentration data were best fitted by a one-compartment model. The selected covariates were body weight with allometric scaling and estimated glomerular filtration rate on clearance. Mean population values for clearance and volume were 1.21 L.h^-1 and 4.8 L, respectively. According to the simulations, a regimen of 100 mg.kg^-1.day^-1 q12 h over 30 min or 100 mg.kg^-1.day^-1 as a continuous infusion was more likely to achieve the PK target in patients with renal failure and in patients with normal or augmented renal clearance, respectively.

CONCLUSIONS

Appropriate cefepime dosing regimens should take renal function into account. Continuous infusions are required in critically ill children with normal or augmented renal clearance, while intermittent infusions are adequate for children with acute renal failure. Close therapeutic drug monitoring is mandatory, given cefepime's narrow therapeutic window.

Microbiological, Clinical, and PK/PD Features of the New Anti-Gram-Negative Antibiotics: β-Lactam/β-Lactamase Inhibitors in Combination and Cefiderocol—An All-Inclusive Guide for Clinicians

Bacterial resistance mechanisms are continuously and rapidly evolving. This is particularly true for Gram-negative bacteria. Over the last decade, the strategy to develop new β-lactam/β-lactamase inhibitors (BLs/BLIs) combinations has paid off and results from phase 3 and real-world studies are becoming available for several compounds. Cefiderocol warrants a separate discussion for its peculiar mechanism of action. Considering the complexity of summarizing and integrating the emerging literature data of clinical outcomes, microbiological mechanisms, and pharmacokinetic/pharmacodynamic properties of the new BL/BLI and cefiderocol, we aimed to provide an overview of data on the following compounds: aztreonam/avibactam, cefepime/enmetazobactam, cefepime/taniborbactam, cefepime/zidebactam, cefiderocol, ceftaroline/avibactam, ceftolozane/tazobactam, ceftazidime/avibactam, imipenem/relebactam, meropenem/nacubactam and meropenem/vaborbactam. Each compound is described in a dedicated section by experts in infectious diseases, microbiology, and pharmacology, with tables providing at-a-glance information.

Ceftazidime dosing in obese patients: is it time for more?

INTRODUCTION

Ceftazidime is used for the treatment of many bacterial infections, including severe P. aeruginosa infections. Like other beta-lactams, inter-individual variability in ceftazidime pharmacokinetics has been described. Due to its related pathophysiological modifications, obesity might influence ceftazidime pharmacokinetics.

AREAS COVERED

The objective of this review is to assess the current state of knowledge about the impact of obesity on ceftazidime treatment. A literature search was conducted on PubMed-MEDLINE (2016-2021) to retrieve pharmacokinetic studies published in English, matching the terms 'ceftazidime' AND 'pharmacokinetics.'

EXPERT OPINION

The impact of obesity on pharmacokinetics is generally poorly known, mainly because obese patients are often excluded from clinical studies. However, the published literature clearly shows that obese patients have significantly lower ceftazidime concentrations. This could be explained by increased volume of distribution and clearance. This low exposure represents a major factor of therapeutic failure, potentially fatal for critically ill patients. While further studies would be useful to better assess the magnitude and understanding of this variability, the use of higher doses of ceftazidime is needed in obese patients. Moreover, therapeutic drug monitoring for dose adaptation is of major interest for these patients, as the efficacy of ceftazidime seems to be directly related to its plasma concentration.

Dried Plasma Spot Based LC-MS/MS Method for Monitoring of Meropenem in the Blood of Treated Patients

Meropenem (MER) is widely used to treat complicated and serious infections. Therapeutic drug monitoring (TDM) provides a valid clinical tool to avoid suboptimal concentrations and dose−related adverse reactions. However, TDM seems to face challenges since the limited stability of MER in plasma makes transport difficult between clinics and laboratories. Dried plasma spot (DPS) sampling is an attractive but underutilized method for TDM that has the desired features of easy collection, storage, and transport, and overcomes known hematocrit (HCT) issues in dried blood spot (DBS) analysis. This study was designed to investigate a DPS−based liquid chromatography−tandem mass spectrometry (LC−MS/MS) method for quantification of MER. The method was developed and validated for DPS and wet plasma samples. Calibration curves were linear (R2 > 0.995) over the concentration range of 0.5−50 µg/mL. Overall accuracy and precision did not exceed 15% and no significant matrix effect was observed. MER has been more stable in DPS than in wet plasma samples. A comparison of DPS and wet plasma concentrations was assessed in 32 patients treated with MER. The results showed that there was no significant difference between the two methods. So the DPS method developed in this study is appropriate and practical for the monitor of MER in the daily clinical laboratory practice.

A sensitive and selective HPLC-MS3 method for therapeutic drug monitoring of meropenem and its validation by comparison with HPLC-MS2 methods

Meropenem, a representative β-lactam antibiotic, is widely used to treat complicated and serious infections. Therefore, it is a great significance to monitor the plasma drug concentration for individualized antimicrobial therapy. This study first describes the development and validation of high performance liquid chromatography-tandem mass spectrometry cubed method for monitoring meropenem in human plasma. Protein precipitation with methanol and a chromatographic analysis time of 7 min make this method is simple and high-throughput. Meropenem was extracted from human plasma with recoveries greater than 94.1%. Calibration curves were linear (R² >0.995) in the concentration range of 0.5-50 μg/mL. Overall accuracy and precision did not exceed 8.0% as well as no significant matrix effect was observed. The novelty of this method is that the triple-stage MS technology improves the selectivity and sensitivity. A comparison of the presented method and traditional liquid chromatography-tandem mass spectrometry method was assessed in 44 patients treated with meropenem and Passing-Bablok regression coefficients and Bland-Altman plots showed that no significant difference between the two methods. So the triple-stage MS method developed in this study is appropriate and practical for the monitor of meropenem in the daily clinical laboratory practice. This article is protected by copyright. All rights reserved.

Effect of therapeutic drug monitoring-based dose optimization of piperacillin/tazobactam on sepsis-related organ dysfunction in patients with sepsis: a randomized controlled trial

PURPOSE

Insufficient antimicrobial exposure is associated with worse outcomes in sepsis. We evaluated whether therapeutic drug monitoring (TDM)-guided antibiotic therapy improves outcomes.

METHODS

Randomized, multicenter, controlled trial from January 2017 to December 2019. Adult patients (n = 254) with sepsis or septic shock were randomly assigned 1:1 to receive continuous infusion of piperacillin/tazobactam with dosing guided by daily TDM of piperacillin or continuous infusion with a fixed dose (13.5 g/24 h if eGFR ≥ 20 mL/min). Target plasma concentration was four times the minimal inhibitory concentration (range ± 20%) of the underlying pathogen, respectively, of Pseudomonas aeruginosa in empiric situation. Primary outcome was the mean of daily total Sequential Organ Failure Assessment (SOFA) score up to day 10.

RESULTS

Among 249 evaluable patients (66.3 ± 13.7 years; female, 30.9%), there was no significant difference in mean SOFA score between patients with TDM (7.9 points; 95% CI 7.1-8.7) and without TDM (8.2 points; 95% CI 7.5-9.0) (p = 0.39). Patients with TDM-guided therapy showed a lower 28-day mortality (21.6% vs. 25.8%, RR 0.8, 95% CI 0.5-1.3, p = 0.44) and a higher rate of clinical (OR 1.9; 95% CI 0.5-6.2, p = 0.30) and microbiological cure (OR 2.4; 95% CI 0.7-7.4, p = 0.12), but these differences did not reach statistical significance. Attainment of target concentration was more common in patients with TDM (37.3% vs. 14.6%, OR 4.5, CI 95%, 2.9-6.9, p < 0.001).

CONCLUSION

TDM-guided therapy showed no beneficial effect in patients with sepsis and continuous infusion of piperacillin/tazobactam with regard to the mean SOFA score. Larger studies with strategies to ensure optimization of antimicrobial exposure are needed to definitively answer the question.

Barriers and Facilitators in the Clinical Implementation of Beta-Lactam Therapeutic Drug Monitoring in Critically Ill Patients: A Critical Review

BACKGROUND

With increasing knowledge of beta-lactam pharmacodynamics and interpatient and intrapatient variability in pharmacokinetics, the usefulness of therapeutic drug monitoring (TDM) is becoming increasingly clear. However, little research has been conducted to identify potential barriers and facilitators in the clinical implementation of beta-lactam TDM. This study provides an overview of the current practices of beta-lactam TDM and barriers and facilitators in its implementation.

METHODS

A systematic search was conducted using the Ovid MEDLINE database in April 2021, without restrictions on the publication date. All studies reporting the implementation of beta-lactam antibiotic TDM in critically ill patients through questionnaires or surveys were included in this review.

RESULTS

Six eligible studies were identified from 215 records, all of which were cross-sectional. All studies identified barriers and facilitators in the implementation of beta-lactam TDM in critically ill patients. The main barriers were insufficient knowledge about various aspects regarding the implementation of beta-lactam TDM and the unavailability of assays. Furthermore, a delay in the acquisition of TDM results reduces the probability of physicians altering drug dosages. Finally, doubts about the cost-effectiveness and clinical effectiveness of beta-lactam TDM in critically ill patients hinder broad implementation. Moreover, to improve the willingness of physicians to use beta-lactam TDM, collaboration between physicians and clinical pharmacists and clinical microbiologists should be strengthened.

CONCLUSIONS

Although the evidence for application of beta-lactam TDM continues to grow, its clinical implementation remains limited. To enable optimal implementation of these antibiotics in critically ill patients, several barriers need to be overcome regarding logistics, equipment availability, clinical evidence, and proof of cost-effectiveness.

Beta-lactam dosing during continuous renal replacement therapy: a survey of practices in french intensive care units

Background

Little information is available on current practice in beta-lactam dosing during continuous renal replacement therapy (CRRT). Optimized dosing is essential for improving outcomes, and there is no consensus on the appropriate dose regimens. The objective of the present study was to describe current practice for beta-lactam dosing during CRRT in intensive care units (ICUs).

Methods

We conducted a nationwide survey by e-mailing an online questionnaire to physicians working in ICUs in France. The questionnaire included three sections: demographic characteristics, CRRT practices, and beta-lactam dosing regimens during CRRT.

Results

157 intensivists completed the questionnaire. Continuous venovenous hemofiltration was the most frequently used CRRT technique, and citrate was the most regularly used anticoagulant. The median prescribed dose at baseline was 30 mL/kg/h. The majority of prescribers (57%) did not reduce beta-lactam dosing during CRRT. The tools were used to adapt dosing regimens during CRRT included guidelines, therapeutic drug monitoring (TDM), and data from the literature. When TDM was used, 100% T > 4 time the MIC was the most common mentioned pharmacokinetic/pharmacodynamic target (53%). Pharmacokinetic software tools were rarely used. Prolonged or continuous infusions were widely used during CRRT (88%). Institutional guidelines on beta-lactam dosing during CRRT were rare. 41% of physicians sometimes consulted another specialist before adapting the dose of antibiotic during CRRT.

Conclusions

Our present results highlight the wide range of beta-lactam dosing practices adopted during CRRT. Personalized TDM and the implementation of Bayesian software appear to be essential for optimizing beta-lactam dosing regimens and improving patient outcomes.

Meropenem Target Attainment and Population Pharmacokinetics in Critically Ill Septic Patients with Preserved or Increased Renal Function

Purpose

Critically ill patients with preserved or increased renal function have been shown to be at risk of underexposure to meropenem. Although many meropenem population pharmacokinetic (PK) models have been published, there is no large prospective population PK study with rich sampling focusing on patients most at risk of suboptimal pharmacokinetic/pharmacodynamic (PK/PD) target attainment. Therefore, the aim of the present study was to evaluate PK/PD target attainment and to perform a thorough covariate screening using population PK modelling of meropenem in septic patients with preserved or increased renal function.

Patients and Methods

A single-centre prospective observational PK study was performed in the intensive care unit (ICU) of the University Hospitals Leuven. Patients with severe sepsis or septic shock and treated with meropenem in the ICU were screened for inclusion. Patients were excluded if they received renal replacement therapy or had an estimated glomerular filtration rate according to the Chronic Kidney Disease Epidemiology collaboration equation <70 mL/min/1.73m² on the day of PK sampling. Successful PK/PD target attainment was defined as an unbound meropenem trough concentration above 2 mg/L or 8 mg/L. Population PK modelling was performed with NONMEM7.4.

Results

In total, 58 patients were included, contributing 345 plasma samples over 70 dosing intervals. The 2 mg/L and 8 mg/L targets were successfully attained in 46% and 11% of all dosing intervals, respectively. A two-compartment population PK model with linear elimination and interindividual variability on clearance best described meropenem PK. The estimated creatinine clearance according to the Cockcroft-Gault equation was the only covariate retained during population PK analysis.

Conclusion

This study provided detailed insight into meropenem PK in critically ill patients with preserved or increased renal function. We observed poor PK/PD target attainment, for which renal function was the only significant covariate.

Trial Registration

This study is registered at ClinicalTrials.gov (NCT03560557).

Identification of factors affecting meropenem pharmacokinetics in critically ill patients: Impact of inflammation on clearance

INTRODUCTION

The purpose of this study was to explore factors influencing meropenem pharmacokinetics (PKs) in critically ill patients by developing a population PK model and to determine the optimal dosing strategy.

METHODS

This prospective observational study involved 12 critically ill patients admitted to the intensive care unit and treated with meropenem 1 g infused over 1 h every 8 h. Blood samples were collected on days 1, 2, and 5 immediately prior to dosing, and at 1, 2, 4, and 6 h after the start of infusion. Population PK parameters were estimated using nonlinear mixed-effects model software.

RESULTS

Meropenem PK was adequately described using a two-compartment model. Typical values of total and inter-compartmental clearance were 9.30 L/h and 9.70 L/h, respectively, and the central and peripheral compartment volumes of distribution were 12.61 L and 7.80 L, respectively. C-reactive protein (CRP) was identified as significant covariate affecting total meropenem clearance. The probability of target attainment (PTA) predicted by Monte Carlo simulations varied according to the patients' CRP. The PTA of 100% time above the minimum inhibitory concentration ≤2 mg/L for bacteria was achieved after a dose of 1 and 2 g infused over 4 h every 8 h in patients with CRP of 30 and 5 mg/dL, respectively.

CONCLUSION

The findings of this study suggest that CRP might be helpful in managing meropenem dosing in critically ill patients. Higher doses and extended infusion may be required to achieve optimal pharmacodynamic targets.

Cefepime precision dosing tool: From Standard to Precise Dose Using Nonparametric Population Pharmacokinetics

Cefepime is the second most common cephalosporin used in U.S. hospitals. We aim to develop and validate cefepime population pharmacokinetic (PK) model and integrate into precision dosing tool for implementation. Two datasets (680 patients) were used to build cefepime PK model in Pmetrics, and three datasets (34 patients) were used for the validation. A separate application dataset (115 patients) was used for the implementation and validation of a precision dosing tool. The model support points and covariates were used to generate the optimal initial dose (OID). Cefepime PK was described by a two-compartment model including weight and creatinine clearance (CrCl) as covariates. The median rate of elimination was 0.30 hr^-1 (adults) and 0.96 hr^-1 (pediatrics), central volume of distribution 13.85 L, and rate of transfer from the central to the peripheral compartments 1.22 hr^-1 and from the peripheral to the central compartments 1.38 hr^-1. After integration in BestDose, the observed vs. predicted cefepime concentration fit using the application dataset was excellent (R²>0.98) and the median difference between observed and what BestDose predicted in a second occasion was 4%. For OID, cefepime 0.5-1g 4-hour infusion q8-24hr with CrCl<70 mL/min was needed to achieve a target range of free trough:MIC 1-4 at MIC 8 mg/L, while continuous infusion was needed for higher CrCl and weight values. In conclusion, we developed and validated a cefepime model for clinical application. The model was integrated in a precision dosing tool for implementation and the median concentration prediction bias was 4%. OID algorithm was provided.

Population Pharmacokinetics of Intravenous Amoxicillin Combined With Clavulanic Acid in Healthy and Critically Ill Dogs

Background: Data regarding antimicrobial pharmacokinetics (PK) in critically ill dogs are lacking and likely differ from those of healthy dogs. The aim of this work is to describe a population PK model for intravenous (IV) amoxicillin–clavulanic acid (AMC) in both healthy and sick dogs and to simulate a range of clinical dosing scenarios to compute PK/PD cutoffs for both populations.

Methods: This study used a prospective clinical trial in normal and critically ill dogs. Twelve client-owned dogs hospitalized in the intensive care unit (ICU) received IV AMC 20 mg/kg every 8 h (0.5-h infusion) during at least 48 h. Eight blood samples were collected at predetermined times, including four trough samples before the next administration. Clinical covariates and outcome were recorded, including survival to discharge and bacteriologic clinical failure. Satellite PK data were obtained de novo from a group of 12 healthy research dogs that were dosed with a single AMC 20 mg/kg IV. Non-linear mixed-effects model was used to estimate the PK parameters (and the effect of health upon them) together with variability within and between subjects. Monte Carlo simulations were performed with seven dosage regimens (standard and increased doses). The correlation between model-derived drug exposure and clinical covariates was tested with Spearman's non-parametric correlation analysis. Outcome was recorded including survival to discharge and bacteriologic clinical failure.

Results: A total of 218 amoxicillin concentrations in plasma were available for healthy and sick dogs. A tricompartmental model best described the data. Amoxicillin clearance was reduced by 56% in sick dogs (0.147 L/kg/h) compared with healthy dogs (0.336 L/kg/h); intercompartmental clearance was also decreased (p <0.01). None of the clinical data covariates were significantly correlated with individual exposure. Monte Carlo simulations showed that higher PK/PD cutoff values of 8 mg/L could be reached in sick dogs by extending the infusion to 3 h or doubling the dose.

Conclusions: The PK of AMC is profoundly different in critically ill dogs compared with normal dogs, with much higher interindividual variability and a lower systemic clearance. Our study allows to generate hypotheses with regard to higher AMC exposure in clinical dogs and provides supporting data to revise current AMC clinical breakpoint for IV administration.