Effect of obesity on the pharmacokinetics of antimicrobials in critically ill patients: A structured review

Evaluation and implementation of optimized antimicrobial dosing strategies in obese and underweight patients

PURPOSE

We aimed to develop and implement dosing recommendations for antimicrobials in obese and underweight patients within an academic hospital, and assess their impact on antibiotic prescribing.

METHODS

A multi-step approach project was performed. First, obese and underweight patient prevalence and antimicrobial prescription frequency was determined in a point prevalence study. Second and third, a literature review and e-survey provided dosing evidence. Fourth, a consensus meeting was organized to formulate dosing recommendations. Fifth, these were implemented in our clinical validation service as six clinical rules continuously screening patients' records for potentially inappropriate prescriptions (PIPs). Uptake was evaluated by documenting the number of advices and acceptance rate. Last, an interrupted time series analysis (ITS) compared pre- and post-implementation periods to measure the impact of the intervention on residual PIPs/day. A residual PIP was defined as a PIP which persisted up to 48 h.

RESULTS

First, 41% of 15.896 hospitalized patients received antimicrobials over 20 days; of which 12% were obese and 9% underweight. Antibiotics were predominantly prescribed according to standard dosing regimens, adjusted to renal function. Next, six dosing recommendations, derived from literature, survey, and consensus, were implemented. In the fifth step, during an 18-week period, 219 advices were given, with 86% acceptance rate. Last, in the ITS analysis, at preintervention, a median of 75% residual PIPs/day existed, reduced to 0% postintervention. Use of clinical rules resulted in a significant immediate 84% relative reduction in residual PIPs (95% CI 0.55-0.94).

CONCLUSION

After conducting a literature review, e-survey, and seeking consensus from a panel of experts, dosing recommendations for antimicrobial treatment in both obese and underweight patients were developed. These recommendations have been successfully implemented into clinical practice, addressing the specific needs of these patient populations.

Vancomycin loading dose individualization in a population of obese patients undergoing haemodialysis based on population pharmacokinetic model

This study aimed to develop a vancomycin population pharmacokinetic model in obese adult patients treated with intermittent haemodialysis and propose a model-based loading dose strategy ensuring attainment of newly recommended AUC-based PK/PD target. Retrospective cross-sectional analysis was performed among obese haemodialysis dependent adult patients treated with intravenous vancomycin. A pharmacokinetic population model was developed using a nonlinear mixed-effects modelling approach and Monte Carlo simulations were used to identify the optimal loading dose for PK/PD target attainment during the first 48 h of treatment. Therapeutic drug monitoring data from 27 patients with a BMI of 30.2-52.9 kg/m2 were analysed. Among all tested variables, only LBM as a covariate of vancomycin Vd significantly improved the model, while vancomycin CL did not correlate with any of the tested variables. The median (IQR) value from the conditional mean of individual estimates of Vd and CL was 68.4 (56.6-84.2) L and 0.86 (0.79-0.90) L/h, respectively. To ensure optimal vancomycin exposure during the first 48 h of therapy, the vancomycin loading dose of 1500, 1750, 2000, 2250, 2500 and 2750 mg should be administered to obese patients with a lean body mass of ˂50, 50-60, 60-70, 70-80, 80-85 and >85 kg, respectively.

Pooled Population Pharmacokinetic Analysis and Dose Recommendations for Ciprofloxacin in Intensive Care Unit Patients with Obesity

Recent studies have explored the influence of obesity and critical illness on ciprofloxacin pharmacokinetics. However, variation across the subpopulation of individuals with obesity admitted to the intensive care unit (ICU) with varying renal function remains unexamined. This study aims to characterize ciprofloxacin pharmacokinetics in ICU patients with obesity and provide dose recommendations for this special population. Individual patient data of 34 ICU patients with obesity (BMI >30 kg/m2) from four studies evaluating ciprofloxacin pharmacokinetics in ICU patients were pooled and combined with data from a study involving 10 individuals with obesity undergoing bariatric surgery. All samples were collected after intravenous administration. Non-linear mixed effects modeling and simulation were used to develop a population pharmacokinetic model and describe ciprofloxacin exposure in plasma. Model-based dose evaluations were performed using a pharmacokinetic/pharmacodynamic target of AUC/MIC >125. The data from patients with BMI ranging from 30.2 to 58.1 were best described by a two-compartment model with first-order elimination and a proportional error model. The inclusion of Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) as a covariate on clearance reduced inter-individual variability from 57.3% to 38.5% (P < .001). Neither body weight nor ICU admission significantly influenced clearance or volume of distribution. Renal function is a viable predictor for ciprofloxacin clearance in ICU patients with obesity, while critical illness and body weight do not significantly alter clearance. As such, body weight and critical illness do not need to be accounted for when dosing ciprofloxacin in ICU patients with obesity. Individuals with CKD-EPI >60 mL/min/1.73 m2 may require higher dosages for the treatment of pathogens with minimal inhibitory concentration ≥0.25 mg/L.

Updated antimicrobial dosing recommendations for obese patients

The prevalence of obesity has increased considerably in the last few decades. Pathophysiological changes in obese patients lead to pharmacokinetic (PK) and pharmacodynamic (PD) alterations that can condition the correct exposure to antimicrobials if standard dosages are used. Inadequate dosing in obese patients can lead to toxicity or therapeutic failure. In recent years, additional antimicrobial PK/PD data, extended infusion strategies, and studies in critically ill patients have made it possible to obtain data to provide a better dosage in obese patients. Despite this, it is usually difficult to find information on drug dosing in this population, which is sometimes contradictory. This is a comprehensive review of the dosing of different types of antimicrobials (antibiotics, antifungals, antivirals, and antituberculosis drugs) in obese patients, where the literature on PK and possible dosing strategies in obese adults was critically assessed.

[An online tool to personalize the drug-doses for obese adults]

BACKGROUND

Between 1975 and 2014, the number of people suffering from obesity tripled, reaching 17% of the adult population in France and more than 35% in the United States. Obesity is defined by a Body Mass Index (BMI)>30kg/m2 and characterized by a significant accumulation of adipose tissue responsible for the increase in weight. This accumulation leads to physiological changes capable of modifying the pharmacokinetics of drugs, which can lead to the administration of inappropriate doses. For this reason, some significant dosage adjustments are necessary for obese patients. However, data on these adaptations are not easily accessible and sometimes complex to implement in practice.

AIM

To perform a new online tool allowing to calculate and propose an adjusted dose of a drug that should be administered to an obese patient.

METHOD

(i) carrying out an extensive bibliographic research according to the PRISMA methodology; and (ii) the development of a new website site proposing an adjusted dose for obese patients.

RESULTS

Firstly, 49 reviews concerning the dose adaptation have been evaluated and, secondly, 319 articles have been selected. Among them, 204 articles have been included in the database to justify the adjusted dose of 84 drugs and administration methods including antibiotics, antifungals, anticoagulants or even cancer drugs. This database is available online through a calculator on the website named Adapt'Obese. Thus, with the sex, height and weight of an obese patient, Adapt'Obese proposes a personalized and adjusted dose of the drug to administer.

PERSPECTIVES

Other drugs will be added soon, and functional improvements are planned, with the aim of adapting the dosages in obese patients, as for patients with renal insufficiency.

External Validation of Obese/Critically Ill Vancomycin Population Pharmacokinetic Models in Critically Ill Patients Who Are Obese

Obesity combined with critical illness might increase the risk of acquiring infections and hence mortality. In this patient population the pharmacokinetics of antimicrobials vary significantly, making antimicrobial dosing challenging. The objective of this study was to assess the predictive performance of published population pharmacokinetic models of vancomycin in patients who are critically ill or obese for a cohort of critically ill patients who are obese. This was a multi-center retrospective study conducted at 2 hospitals. Adult patients with a body mass index of ≥30 kg/m2 were included. PubMed was searched for published population pharmacokinetic studies in patients who were critically ill or obese. External validation was performed using Monolix software. A total of 4 models were identified in patients who were obese and 5 models were identified in patients who were critically ill. In total, 138 patients who were critically ill and obese were included, and the most accurate models for these patients were the Goti and Roberts models. In our analysis, models in patients who were critically ill outperformed models in patients who were obese. When looking at the most accurate models, both the Goti and the Roberts models had patient characteristics similar to ours in terms of age and creatinine clearance. This indicates that when selecting the proper model to apply in practice, it is important to account for all relevant variables, besides obesity.

Clinical and demographic factors affecting trough levels of isavuconazole in critically ill patients with or without COVID-19

BACKGROUND

The broad-spectrum antifungal isavuconazole is administered to treat invasive aspergillosis and mucormycosis.

OBJECTIVES

Isavuconazole plasma concentrations in critically ill ICU patients with or without COVID-19 and invasive fungal infection were determined, and factors for sub-therapeutic drug levels (<1 μg/mL) were evaluated.

PATIENTS AND METHODS

Isavuconazole plasma levels were measured as part of therapeutic drug monitoring (TDM) in ICUs of a tertiary hospital. Concentrations determined 20-28 h after previous dosing were defined as trough (Cmin ) levels. A total of 160 Cmin levels from 62 patients with invasive fungal infections were analysed, 30 of which suffering from COVID-19. Patient characteristics included into univariable and multivariable analyses were gender, age, COVID-19 status, body mass index (BMI), sepsis-related organ failure (SOFA) score, renal replacement therapy (RRT) and extracorporeal membrane oxygenation (ECMO) requirement.

RESULTS

The mean Cmin of isavuconazole in all patients was 1.64 μg/mL (interquartile range 0.83-2.24 μg/mL, total range 0.24-5.67 μg/mL). In total, 34.4% of the Cmin values (corresponding to 46.8% of patients) were below a threshold concentration of 1 μg/mL. Drug concentrations between patients with or without COVID-19 did not differ (p = .43). In contrast, levels were significantly lower in patients with female sex (p = .0007), age ≤ 65 years (p = .002), BMI > 25 (p = .006), SOFA score > 12 (p = .026), RRT (p = .017) and ECMO requirement (p = .001).

CONCLUSIONS

Isavuconazole plasma levels can be negatively affected by patients' risk factors, supportive renal replacement and ECMO therapy. Future prospective studies analysing the relevance of isavuconazole drug levels in ICU patient outcome are urgently needed.

Predicting Beta-Lactam Target Non-Attainment in ICU Patients at Treatment Initiation: Development and External Validation of Three Novel (Machine Learning) Models

In the intensive care unit (ICU), infection-related mortality is high. Although adequate antibiotic treatment is essential in infections, beta-lactam target non-attainment occurs in up to 45% of ICU patients, which is associated with a lower likelihood of clinical success. To optimize antibiotic treatment, we aimed to develop beta-lactam target non-attainment prediction models in ICU patients. Patients from two multicenter studies were included, with intravenous intermittent beta-lactam antibiotics administered and blood samples drawn within 12-36 h after antibiotic initiation. Beta-lactam target non-attainment models were developed and validated using random forest (RF), logistic regression (LR), and naïve Bayes (NB) models from 376 patients. External validation was performed on 150 ICU patients. We assessed performance by measuring discrimination, calibration, and net benefit at the default threshold probability of 0.20. Age, sex, serum creatinine, and type of beta-lactam antibiotic were found to be predictive of beta-lactam target non-attainment. In the external validation, the RF, LR, and NB models confirmed good discrimination with an area under the curve of 0.79 [95% CI 0.72-0.86], 0.80 [95% CI 0.73-0.87], and 0.75 [95% CI 0.67-0.82], respectively, and net benefit in the RF and LR models. We developed prediction models for beta-lactam target non-attainment within 12-36 h after antibiotic initiation in ICU patients. These online-accessible models use readily available patient variables and help optimize antibiotic treatment. The RF and LR models showed the best performance among the three models tested.

Pharmacokinetics of obese adults: Not only an increase in weight

Obesity is a pathophysiological state defined by a body mass index > 30 kg/m2 and characterized by an adipose tissue accumulation leading to an important weight increased. Several pathologies named comorbidities such as cardiovascular disease, type 2 diabetes and cancer make obesity the fifth cause of death in the world. Physiological changes impact the four main phases of pharmacokinetics of some drugs and leads to an inappropriate drug-dose. For absorption, the gastrointestinal transit is accelerated, and the gastric empty time is shortened, that can reduce the solubilization and absorption of some oral drugs. The drug distribution is probably the most impacted by the obesity-related changes because the fat mass (FM) increases at the expense of the lean body weight (LBW), leading to an important increase of the volume of distribution for lipophilic drugs and a low or moderately increase of this parameter for hydrophilic drugs. This modification of the distribution may require drug-dose adjustments. By various mechanisms, the metabolism and elimination of drugs are impacted by obesity and should be considered as similar or lower than that non-obese patients. To better understand the necessary drug-dose adjustments in obese patients, a narrative review of the literature was conducted to highlight the main elements to consider in the therapeutic management of adult obese patients.

Peri-operative pharmacokinetics of cefazolin prophylaxis during valve replacement surgery

OBJECTIVE

There is little prospective data to guide effective dosing for antibiotic prophylaxis during surgery requiring cardiopulmonary bypass (CPB). We aim to describe the effects of CPB on the population pharmacokinetics (PK) of total and unbound concentrations of cefazolin and to recommend optimised dosing regimens.

METHODS

Patients undergoing CPB for elective cardiac valve replacement were included using convenience sampling. Intravenous cefazolin (2g) was administered pre-incision and re-dosed at 4 hours. Serial blood and urine samples were collected and analysed using validated chromatography. Population PK modelling and Monte-Carlo simulations were performed using Pmetrics® to determine the fractional target attainment (FTA) of achieving unbound concentrations exceeding pre-defined exposures against organisms known to cause surgical site infections for 100% of surgery (100% fT>MIC).

RESULTS

From the 16 included patients, 195 total and 64 unbound concentrations of cefazolin were obtained. A three-compartment linear population PK model best described the data. We observed that cefazolin 2g 4-hourly was insufficient to achieve the FTA of 100% fT>MIC for Staphylococcus aureus and Escherichia coli at serum creatinine concentrations ≤ 50 μmol/L and for Staphylococcus epidermidis at any of our simulated doses and serum creatinine concentrations. A dose of cefazolin 3g 4-hourly demonstrated >93% FTA for S. aureus and E. coli.

CONCLUSIONS

We found that cefazolin 2g 4-hourly was not able to maintain concentrations above the MIC for relevant pathogens in patients with low serum creatinine concentrations undergoing cardiac surgery with CPB. The simulations showed that optimised dosing is more likely with an increased dose and/or dosing frequency.

Weighing the Odds: Novel β-Lactam/β-Lactamase Inhibitor Use in Hospital-Acquired and Ventilator-Associated Pseudomonas aeruginosa Pneumonia for Patients Who Are Morbidly Obese

Background

Pseudomonas aeruginosa is a leading cause of hospital-acquired and ventilator-associated bacterial pneumonia (HABP/VABP). Novel β-lactam/β-lactamase inhibitor (BL/BLI) combinations are often used for these infections; however, limited data exist to guide the dosing of BL/BLI in patients who are morbidly obese. Thus, we sought to evaluate the clinical and safety endpoints of patients who are morbidly obese (body mass index ≥35 kg/m2) and non-morbidly obese (<35 kg/m2) and receiving BL/BLI for P aeruginosa HABP/VABP.

Methods

This retrospective study was based on a cohort of patients hospitalized at 2 urban academic medical centers in Detroit, Michigan, from August 2014 through February 2021 with P aeruginosa HABP/VABP who were receiving BL/BLI (ceftazidime/avibactam, ceftolozane/tazobactam, or meropenem/vaborbactam) for ≥72 continuous hours. The primary endpoint was presumed treatment failure, defined as the presence of all-cause in-hospital mortality or the continuation of infectious symptoms. Analyses were adjusted for possible confounding with inverse probability of treatment weighting. Multivariable regression was used to identify predictors of treatment failure.

Results

In total, 285 patients with HABP (61.4%) and/or VABP (56.1%) were enrolled (morbidly obese, n = 95; non-morbidly obese, n = 190). The median Acute Physiology and Chronic Health Evaluation II score was 23 (IQR, 13-26), and 60% of patients were admitted to the intensive care unit at index culture collection. Patients who were morbidly obese demonstrated significantly greater odds of presumed treatment failure vs those who were non-morbidly obese (58.9% vs 37.9%, respectively; adjusted odds ratio, 1.675 [95% CI, 1.465-1.979]). In multivariable analysis, morbid obesity (1.06; 95% CI, 1.02-1.79), prolonged time to BL/BLI initiation (1.47; 95% CI, 1.28-2.66), renal dose-adjusted BL/BLI in the first 48 hours of therapy (1.12; 95% CI, 1.09-1.75), and continuous renal replacement therapy during BL/BLI therapy (1.35; 95% CI, 1.06-1.68) were independently associated with increased odds of presumed treatment failure.

Conclusions

Among hospitalized patients receiving BL/BLI for P aeruginosa HABP/VABP, those who were morbidly obese had significantly greater odds of presumed treatment failure when compared with those who were non-morbidly obese.

Rationale and evidence for the use of new beta-lactam/beta-lactamase inhibitor combinations and cefiderocol in critically ill patients

BACKGROUND

Healthcare-associated infections involving Gram-negative bacteria (GNB) with difficult-to-treat resistance (DTR) phenotype are associated with impaired patient-centered outcomes and poses daily therapeutic challenges in most of intensive care units worldwide. Over the recent years, four innovative β-lactam/β-lactamase inhibitor (BL/BLI) combinations (ceftolozane-tazobactam, ceftazidime-avibactam, imipenem-relebactam and meropenem-vaborbactam) and a new siderophore cephalosporin (cefiderocol) have been approved for the treatment of certain DTR-GNB infections. The literature addressing their microbiological spectrum, pharmacokinetics, clinical efficacy and safety was exhaustively audited by our group to support the recent guidelines of the French Intensive Care Society on their utilization in critically ill patients. This narrative review summarizes the available evidence and unanswered questions on these issues.

METHODS

A systematic search for English-language publications in PUBMED and the Cochrane Library database from inception to November 15, 2022.

RESULTS

These drugs have demonstrated relevant clinical success rates and a reduced renal risk in most of severe infections for whom polymyxin- and/or aminoglycoside-based regimen were historically used as last-resort strategies-namely, ceftazidime-avibactam for infections due to Klebsiella pneumoniae carbapenemase (KPC)- or OXA-48-like-producing Enterobacterales, meropenem-vaborbactam for KPC-producing Enterobacterales, ceftazidime-avibactam/aztreonam combination or cefiderocol for metallo-β-lactamase (MBL)-producing Enterobacterales, and ceftolozane-tazobactam, ceftazidime-avibactam and imipenem-relebactam for non-MBL-producing DTR Pseudomonas aeruginosa. However, limited clinical evidence exists in critically ill patients. Extended-infusion scheme (except for imipenem-relebactam) may be indicated for DTR-GNB with high minimal inhibitory concentrations and/or in case of augmented renal clearance. The potential benefit of combining these agents with other antimicrobials remains under-investigated, notably for the most severe presentations. Other important knowledge gaps include pharmacokinetic information in particular situations (e.g., pneumonia, other deep-seated infections, and renal replacement therapy), the hazard of treatment-emergent resistance and possible preventive measures, the safety of high-dose regimen, the potential usefulness of rapid molecular diagnostic tools to rationalize their empirical utilization, and optimal treatment durations. Comparative clinical, ecological, and medico-economic data are needed for infections in whom two or more of these agents exhibit in vitro activity against the causative pathogen.

CONCLUSIONS

New BL/BLI combinations and cefiderocol represent long-awaited options for improving the management of DTR-GNB infections. Several research axes must be explored to better define the positioning and appropriate administration scheme of these drugs in critically ill patients.

The place of new antibiotics for Gram-negative bacterial infections in intensive care: report of a consensus conference

INTRODUCTION

New beta-lactams, associated or not with beta-lactamase inhibitors (NBs/BIs), can respond to the spread of carbapenemase-producing enterobacteriales and nonfermenting carbapenem-resistant bacteria. The risk of emergence of resistance to these NBs/BIs makes guidelines necessary. The SRLF organized a consensus conference in December 2022.

METHODS

An ad hoc committee without any conflict of interest (CoI) with the subject identified the molecules (ceftolozane-tazobactam, ceftazidime-avibactam, imipenem-cilastatin-relebactam, meropenem-vaborbactam and cefiderocol); defined 6 generic questions; drew up a list of subquestions according to the population, intervention, comparison and outcomes (PICO) model; and reviewed the literature using predefined keywords. The quality of the data was assessed using the GRADE methodology. Seven experts in the field proposed their own answers to the questions in a public session and answered questions from the jury (a panel of 10 critical-care physicians without any CoI) and the public. The jury then met alone for 48 h to write its recommendations. Due to the frequent lack of powerful studies that have used clinically important criteria of judgment, the recommendations were formulated as expert opinions as often as necessary.

RESULTS

The jury provided 17 statements answering 6 questions: (1) Is there a place in the ICU for the probabilistic use of new NBs/IBs active against Gram-negative bacteria? (2) In the context of documented infections with sensitivity to several of these molecules, are there pharmacokinetic, pharmacodynamic, ecological or medico-economic elements for prioritization? (3) What are the possible combinations with these molecules and in what context? (4) Should we integrate these new molecules into a carbapenem-sparing strategy? (5) What pharmacokinetic and pharmacodynamic data are available to optimize their mode of administration in critically ill patients? (6) What are the dosage adaptations in cases of renal insufficiency, hepatocellular insufficiency or obesity?

CONCLUSION

These recommendations should optimize the use of NBs/BIs in ICU patients.

Impact of body size on efficacy of high-dose dual therapy for Helicobacter pylori eradication

BACKGROUND

High-dose dual therapy (HDDT) is an emerging and promising therapeutic regime for Helicobacter pylori (H. pylori) eradication. However, the pharmacokinetics of the components of HDDT, amoxicillin and proton pump inhibitor, are likely to be affected by body size. In this study, we aimed to find out the impact of body size on the efficacy of HDDT.

METHODS

We collected the medical data of 385 treatment-naive patients infected with H. pylori who received HDDT (esomeprazole 20 mg and amoxicillin 750 mg four times daily) for 14 days from July 2020 to December 2021. The associations among the eradication efficacy, adverse events, and variables (sex, age, height, body weight, body mass index (BMI), body surface area (BSA), smoking, drinking, etc.) were analyzed respectively in our study. Among these factors, continuous variables were classified into categorical variables using the cut-off values which were calculated by receiver operating characteristic analysis.

RESULTS

The eradication rate of HDDT was 89.9%. There were 55 (14.3%) patients who occurred adverse events during the treatment. Patients with height <170.5 cm, body weight <60.5 kg, BMI <20.55 kg/m² , BSA <1.69 m² had a higher eradication rate (92.1% vs. 84.0%, 93.1% vs. 86.8%, 96.0% vs. 87.8%, 93.4% vs. 84.8%, all p < .05). The multivariate analysis showed that BSA ≥1.69 m² (OR 2.53, 95% CI: 1.28-4.99, p = .007) was the only independent predictor of eradication failure.

CONCLUSION

HDDT could achieve better eradication efficacy in patients with small BSA. Clinicians should be aware of the impact of BSA on the H. pylori eradication rate and pay more attention to patients with large BSA.

Comprehensive guidance for antibiotic dosing in obese adults: 2022 update

Drug dosing in obese patients continues to be challenging due to a lack of high-quality evidence to guide dosing recommendations. We first published guidance for antibiotic dosing in obese adults in 2017, in which we critically reviewed articles identified from a broad search strategy to develop dosing recommendations for 35 antimicrobials. In this updated narrative review, we searched Pubmed, Web of Science, and the Cochrane Library using Medical Subject Headings including anti-infectives, specific generic antimicrobial names, obese, pharmacokinetics, and others. We reviewed 393 articles, cross-referenced select cited references, and when applicable, referenced drug databases, package inserts, and clinical trial data to update dosing recommendations for 41 antimicrobials. Most included articles were pharmacokinetic studies, other less frequently included articles were clinical studies (mostly small, retrospective), case reports, and very rarely, guidelines. Pharmacokinetic changes are frequently reported, can be variable, and sometimes conflicting in this population, and do not always translate to a documented difference in clinical outcomes, yet are used to inform dosing strategies. Extended infusions, high doses, and therapeutic drug monitoring remain important strategies to optimize dosing in this population. Additional studies are needed to clinically validate proposed dosing strategies, clarify optimal body size descriptors, dosing weight scalars, and estimation method of renal function in obese patients.

Pharmacokinetics of flomoxef in plasma, peritoneal fluid, peritoneum, and subcutaneous adipose tissue of patients undergoing lower gastrointestinal surgery: Dosing considerations based on site-specific pharmacodynamic target attainment

INTRODUCTION

Flomoxef is generally used to treat abdominal infections and as antibiotic prophylaxis during lower gastrointestinal surgery. It is reportedly effective against extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae and an increasingly valuable alternative to carbapenems. However, its abdominal pharmacokinetics remain unclear. Herein, pharmacokinetic analysis of flomoxef in the abdominal tissue was conducted to simulate dosing regimens for pharmacodynamic target attainment in abdominal sites.

METHODS

Flomoxef (1 g) was administered intravenously to a patient 30 min before commencing elective lower gastrointestinal surgery. Samples of plasma, peritoneal fluid, peritoneum, and subcutaneous adipose tissue were collected during surgery. The flomoxef tissue concentrations were measured. Accordingly, non-compartmental and compartmental pharmacokinetic parameters were calculated, and simulations were conducted to evaluate site-specific pharmacodynamic target values.

RESULTS

Overall, 41 plasma samples, 34 peritoneal fluid samples, 38 peritoneum samples, and 41 subcutaneous adipose samples from 10 patients were collected. The mean peritoneal fluid-to-plasma ratio in the areas under the drug concentration-time curve was 0.68, the mean peritoneum-to-plasma ratio was 0.40, and the mean subcutaneous adipose tissue-to-plasma was 0.16. The simulation based on these results showed the dosing regimens (q8h [3 g/day] and q6h [4 g/day]) achieved the bactericidal effect (% T > minimum inhibitory concentration [MIC] = 40%) in all tissues at an MIC of 1 mg/L.

CONCLUSIONS

We elucidated the pharmacokinetics of flomoxef and simulated pharmacodynamics target attainment in the abdominal tissue. This study provides evidence concerning the use of optimal dosing regimens for treating abdominal infection caused by strains like ESBL-producing bacteria.

Dose optimization of vancomycin in obese patients: A systematic review

Background: Dose optimization of vancomycin plays a substantial role in drug pharmacokinetics because of the increased incidence of obesity worldwide. This systematic review was aimed to highlight the current dosing strategy of vancomycin among obese patients. Methods: This systematic review was in concordance with Preferred Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. The literature search was carried out on various databases such as Scopus, PubMed/MEDLINE, ScienceDirect and EMBASE using Keywords and MeSH terms related to vancomycin dosing among obese patients. Google Scholar was also searched for additional articles. The English language articles published after January, 2000 were included in this study. The quality of the study was assessed using different assessment tools for cohort, and case reports. Results: A total of 1,029 records were identified. After screening, 18 studies were included for the final review. Of total, twelve studies are retrospective and remaining six are case-control studies. A total of eight studies were conducted in pediatrics while remaining studies were conducted in adult population. Most of the studies reported the dosing interval every 6-8 h. Differences in target trough concentration exist with respect to target ranges. The administration of loading dose (20-25 mg/kg) followed by maintenance dose (15-25 mg/kg) of vancomycin is recommended in adult patients to target therapeutic outcomes. Moreover, a dose of 40-60 mg/kg/day appears appropriate for pediatric patients. Conclusion: The initial dosing of vancomycin based on TBW could be better predictor of vancomycin trough concentration. However, the clinical significance is uncertain. Therefore, more studies are needed to evaluate the dosing strategy of vancomycin in overweight or obese patients.

Ten-Day Vonoprazan-Amoxicillin Dual Therapy as a First-Line Treatment of Helicobacter pylori Infection Compared With Bismuth-Containing Quadruple Therapy

INTRODUCTION

No study has investigated the efficacy and safety of vonoprazan-amoxicillin dual therapy compared with bismuth quadruple therapy (B-quadruple). This study aimed to evaluate the efficacy and safety of 10-day vonoprazan-amoxicillin dual therapy as a first-line treatment of Helicobacter pylori infection compared with B-quadruple and to explore the optimal dosage of amoxicillin in the dual therapy.

METHODS

A total of 375 treatment-naive, H. pylori-infected subjects were randomly assigned in a 1:1:1 ratio into 3 regimen groups including VHA-dual (vonoprazan 20 mg twice/day + amoxicillin 750 mg 4 times/day), VA-dual (vonoprazan 20 mg + amoxicillin 1,000 mg twice/day), and B-quadruple (esomeprazole 20 mg + bismuth 200 mg + amoxicillin 1,000 mg + clarithromycin 500 mg twice/day). Eradication rates, adverse events (AEs), and compliance were compared between 3 groups.

RESULTS

The eradication rates of B-quadruple, VHA-dual, and VA-dual were 90.9%, 93.4%, and 85.1%, respectively, by per-protocol analysis; 89.4%, 92.7%, and 84.4%, respectively, by modified intention-to-treat analysis; 88.0%, 91.2%, and 82.4%, respectively, by intention-to-treat analysis. The efficacy of the VHA-dual group was not inferior to the B-quadruple group (P < 0.001), but VA-dual did not reach a noninferiority margin of -10%. The AEs rates of the B-quadruple group were significantly higher than those of the VHA-dual (P = 0.012) and VA-dual (P = 0.001) groups. There was no significant difference in medication compliance among 3 treatment groups (P = 0.995).

CONCLUSIONS

The 10-day VHA-dual therapy provided satisfactory eradication rates of >90%, lower AEs rates, and similar adherence compared with B-quadruple therapy as a first-line therapy for H. pylori infection. However, the efficacy of VA-dual therapy was not acceptable.

Pharmacokinetics, Pharmacodynamics, and Dosing Considerations of Novel β-Lactams and β-Lactam/β-Lactamase Inhibitors in Critically Ill Adult Patients: Focus on Obesity, Augmented Renal Clearance, Renal Replacement Therapies, and Extracorporeal Membrane Oxygenation

OBJECTIVE

Dose optimization of novel β-lactam antibiotics (NBLA) has become necessary given the increased prevalence of multidrug-resistant infections in intensive care units coupled with the limited number of available treatment options. Unfortunately, recommended dose regimens of NBLA based on PK/PD indices are not well-defined for critically ill patients presenting with special situations (i.e., obesity, extracorporeal membrane oxygenation (ECMO), augmented renal clearance (ARC), and renal replacement therapies (RRT)). This review aimed to discuss and summarize the available literature on the PK/PD attained indices of NBLA among critically ill patients with special circumstances.

DATA SOURCES

PubMed, MEDLINE, Scopus, Google Scholar, and Embase databases were searched for studies published between January 2011 and May 2022.

STUDY SELECTION AND DATA EXTRACTION

Articles relevant to NBLA (i.e., ceftolozane/tazobactam, ceftazidime/avibactam, cefiderocol, ceftobiprole, imipenem/relebactam, and meropenem/vaborbactam) were selected. The MeSH terms of "obesity", "augmented renal clearance", "renal replacement therapy", "extracorporeal membrane oxygenation", "pharmacokinetic", "pharmacodynamic" "critically ill", and "intensive care" were used for identification of articles. The search was limited to adult humans' studies that were published in English. A narrative synthesis of included studies was then conducted accordingly.

DATA SYNTHESIS

Available evidence surrounding the use of NBLA among critically ill patients presenting with special situations was limited by the small sample size of the included studies coupled with high heterogeneity. The PK/PD target attainments of NBLA were reported to be minimally affected by obesity and/or ECMO, whereas the effect of renal functionality (in the form of either ARC or RRT) was more substantial.

CONCLUSION

Critically ill patients presenting with special circumstances might be at risk of altered NBLA pharmacokinetics, particularly in the settings of ARC and RRT. More robust, well-designed trials are still required to define effective dose regimens able to attain therapeutic PK/PD indices of NBLA when utilized in those special scenarios, and thus aid in improving the patients' outcomes.

Tigecycline Soft Tissue Penetration in Obese and Non-obese Surgical Patients Determined by Using In Vivo Microdialysis

Background and Objective

Tigecycline, a broad-spectrum glycylcycline antibiotic, is approved for use at a fixed dose irrespective of body weight. However, its pharmacokinetics may be altered in obesity, which would impact on the antibiotic’s effectiveness. The objective of this study was to investigate the plasma and subcutaneous tissue concentrations of tigecycline in obese patients compared with those in a non-obese control group.

Methods

Fifteen obese patients (one class II and 14 class III) undergoing bariatric surgery and 15 non-obese patients undergoing intra-abdominal surgery (mainly tumour resection) received a single dose of 50 or 100 mg tigecycline as an intravenous short infusion. Tigecycline concentrations were measured up to 8 h after dosing in plasma (total concentration), in ultrafiltrate of plasma (free concentration), and in microdialysate from subcutaneous tissue, respectively.

Results

In obese patients, total peak plasma concentration (1.31 ± 0.50 vs 2.27 ± 1.40 mg/L) and the area under the concentration–time curve from 0 to 8 h (AUC_8h,plasma: 2.15 ± 0.42 vs 2.74 ± 0.73 h⋅mg/L), as normalized to a 100 mg dose, were significantly lower compared with those of non-obese patients. No significant differences were observed regarding the free plasma concentration, as determined by ultrafiltration, or the corresponding AUC_8h (fAUC_8h,plasma). Concentrations in interstitial fluid (ISF) of subcutaneous tissue were lower than the free plasma concentrations in both groups, and they were lower in obese compared to non-obese patients: the AUC_8h in ISF (AUC_8h,ISF) was 0.51 ± 0.22 h⋅mg/L in obese and 0.79 ± 0.23 h⋅mg/L in non-obese patients, resulting in a relative tissue drug exposure (AUC_8h,ISF/fAUC_8h,plasma) of 0.38 ± 0.19 and 0.63 ± 0.24, respectively.

Conclusion

Following a single dose of tigecycline, concentrations in the ISF of subcutaneous adipose tissue are decreased in heavily obese subjects, calling for an increased loading dose.

EU Clinical Trials Registration Number

EudraCT No. 2012-004383-22.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13318-022-00789-2.

Vancomycin dosing in an obese patient with acute renal failure: A case report and review of literature

BACKGROUND

Vancomycin is the most commonly used drug for methicillin-resistant Staphylococcus aureus. The empirical clinical doses of vancomycin based on non-obese patients may not be optimal for obese ones.

CASE SUMMARY

This study reports a case of vancomycin dosing adjustment in an obese patient (body mass index 78.4 kg/m²) with necrotizing fasciitis of the scrotum and left lower extremity accompanied with acute renal failure. Dosing adjustment was performed based on literature review and factors that influence pharmacokinetic parameters are analyzed. The results of the blood drug concentration monitoring confirmed the successful application of our dosing adjustment strategy in this obese patient. Total body weight is an important consideration for vancomycin administration in obese patients, which affects the volume of distribution and clearance of vancomycin. The alterations of pharmacokinetic parameters dictate that vancomycin should be dose-adjusted when applied to obese patients. At the same time, the pathophysiological status of patients, such as renal function, which also affects the dose adjustment of the patient, should be considered.

CONCLUSION

Monitoring vancomycin blood levels in obese patients is critical to help adjust the dosing regimen to ensure that vancomycin concentrations are within the effective therapeutic range and to reduce the incidence of renal injury.

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.

Ensuring target concentrations of antibiotics in critically ill patients through dose adjustment

INTRODUCTION

Antibiotics are commonly prescribed in critical care, and given the large variability of pharmacokinetic (PK) parameters in these patients, drug PK frequently varies during therapy with the risk of either treatment failure or toxicity. Therefore, adequate antibiotic dosing in critically ill patients is very important.

AREAS COVERED

This review provides an overview of the basic principles of PK and pharmacodynamics of antibiotics and the main patient and pathogen characteristics that may affect the dosage of antibiotics and different approaches to adjust doses.

EXPERT OPINION

Dose adjustment should be done for aminoglycosides and glycopeptides based on daily drug concentration monitoring. For glycopeptides, in particular vancomycin, the residual concentration (Cres) should be assessed daily. For beta-lactam antibiotics, a loading dose should be administered, followed by three different possible approaches, as TDM is rarely available in most centers: 1) antibiotic regimens should be adapted according to renal function and other risk factors; 2) nomograms or software can be used to calculate daily dosing; 3) TDM should be performed 24-48 h after the initiation of treatment; however, the results are required within 24 hours to appropriately adjust dosage regimens. Drug dosing should be reduced or increased according to the TDM results.

Characterizing Safety and Clinical Outcomes Associated with High-Dose Micafungin Utilization in Patients with Proven Invasive Candidiasis

Micafungin is the empiric antifungal agent of choice for the treatment of invasive candidiasis (IC). Pathophysiologic changes that occur in obese and/or critically ill patients can alter micafungin serum concentrations and the probability of target attainment. Although high doses of micafungin have been shown to be safe, clinical outcomes have not been widely evaluated. We conducted a single-center, retrospective observational study evaluating safety and clinical outcomes among adult patients treated with ≥200 mg of micafungin for ≥3 days for proven IC from 1 September 2013 through 1 September 2021. Twenty-three unique encounters for 21 patients were evaluated. The median BMI and APACHE II scores were 37.1 (IQR 28.8–48.9) and 24 (IQR 17.7–31), respectively. The median average daily dose of micafungin was 300 mg (IQR 275–400). Patients were treated with high-dose (HD) micafungin for the entirety of their echinocandin course in 15 encounters (65.2%). Transaminases remained stable, while a trend towards increased alkaline phosphatase was observed. A total of four deaths occurred (17.4%). Patients that died were predominantly young, Hispanic males who were obese and/or critically ill. Future studies are needed to determine the necessity and appropriate placement of HD micafungin in obese and/or critically ill patients.

Modelled target attainment after temocillin treatment in severe pneumonia: systemic and epithelial lining fluid pharmacokinetics of continuous versus intermittent infusions

Objectives: To describe the population pharmacokinetics of temocillin administered via continuous versus intermittent infusion in critically ill patients with pneumonia. Secondary objectives included characterization of epithelial lining fluid (ELF)/plasma penetration ratios and determination of the probability of target attainment (PTA) for a range of MICs. Methods: Thirty-two mechanically ventilated patients who were treated for pneumonia with 6g of temocillin daily for in vitro sensitive pathogens were assigned either to the II (2g every 8h over 0.5h) or to the CI (6g over 24h after a loading dose of 2g) group. A population pharmacokinetic model was developed using unbound plasma and total ELF concentrations of temocillin and related Monte Carlo simulations were performed to assess PTAs. Results: The AUC_0-24 ELF/plasma penetration ratio was 0.73, at steady-state, for both modes of infusion and whatever the level of creatinine clearance. Monte Carlo simulations showed for the minimal pharmacodynamic (PD) targets of 50% T> 1X MIC (II group) and 100% T > 1X MIC (CI group), PK/PD breakpoints of 4 mg/L in plasma and 2 mg/L in ELF and 4mg/L in plasma and ELF, respectively. The breakpoint was 8 mg/L in ELF for both modes of infusion in patients with CL_CR<60mL/min. Conclusion: While CI provides better PKPD indexes, the latter remain below available recommendations for systemic infections, except in case of moderate renal impairment, thereby warranting future clinical studies in order to determine the efficacy of temocillin in severe pneumonia.

Clinical Outcomes with Ertapenem for Pneumonia in Obese versus Nonobese Patients

The objective of this study was to compare the rate of pneumonia resolution in obese (body mass index [BMI], ≥30 kg/m2) and nonobese (BMI, <30 kg/m2) patients treated with 1 gram ertapenem daily. In this retrospective cohort study, we evaluated patients treated at The Ohio State University Wexner Medical Center between 1 January 2015 and 31 August 2020. Patients were included if they were between 18 and 89 years old and received ertapenem for at least 48 hours for pneumonia treatment. Patients were excluded if they were pregnant, were incarcerated, had renal impairment, received antibiotics with Gram-negative activity for a significant period prior to or in addition to ertapenem, and had other concomitant deep-seated infections. The primary outcome of clinical resolution was defined as meeting any of the following three criteria in order of evaluations: discontinuation of antibiotics by day 8 of therapy, afebrile while on ertapenem in addition to a decrease in white blood cell count, or improvement on chest radiograph at day 7 of therapy. A multivariable logistic regression analysis was performed to examine the association between obesity and clinical resolution, while adjusting for proven confounders. There were 76 nonobese and 65 obese patients included. The median patient BMI was 23.7 kg/m2 (21.0 to 26.9) and 35.0 kg/m2 (32.8 to 39.8) for the nonobese and obese cohorts, respectively. Clinical resolution was achieved in 78% (59/76) of nonobese and 75% (49/65) of obese patients (P = 0.75) without an observed difference in the regression model. Outcomes were similar in obese and nonobese patients treated with 1 gram of ertapenem daily for pneumonia.

The Interplay between Host Defense, Infection, and Clinical Status in Septic Patients: A Narrative Review

Sepsis is a life-threatening condition that arises when the body's response to an infection injures its own tissues and organs. Despite significant morbidity and mortality throughout the world, its pathogenesis and mechanisms are not clearly understood. In this narrative review, we aimed to summarize the recent developments in our understanding of the hallmarks of sepsis pathogenesis (immune and adaptive immune response, the complement system, the endothelial disfunction, and autophagy) and highlight novel laboratory diagnostic approaches. Clinical management is also discussed with pivotal consideration for antimicrobic therapy management in particular settings, such as intensive care unit, altered renal function, obesity, and burn patients.

Are Antibiotics Appropriately Dosed in Critically Ill Patients with Augmented Renal Clearance? A Narrative Review

AIMS

Augmented renal clearance (ARC), which is commonly defined as increased renal clearance above 130 ml/min/1.73 m², is a common phenomenon among critically ill patients. The increased elimination rate of drugs through the kidneys in patients with ARC can increase the risk of treatment failure due to the exposure to subtherapeutic serum concentrations of medications and affect the optimal management of infections, length of hospital stay, and outcomes. The main goal of this review article is to summarize the recommendations for appropriate dosing of antibiotics in patients with ARC.

METHODS

This article is a narrative review of the articles that evaluated different dosing regimens of antibiotics in patients with ARC. The keywords "Augmented Renal Clearance," "Critically ill patients," "Drug dosing," "Serum concentration," "Beta-lactams," "Meropenem," "Imipenem," "Glycopeptide," "Vancomycin," "Teicoplanin," "Linezolid," "Colistin," "Aminoglycosides," "Amikacin," "Gentamycin," "Fluoroquinolones," "Ciprofloxacin," and "Levofloxacin" were searched in Scopus, Medline, PubMed, and Google Scholar databases, and pediatric, nonhuman, and non-English studies were excluded.

RESULTS

PK properties of antibiotics including lipophilicity or hydrophilicity, protein binding, the volume of distribution, and elimination rate that affect drug concentration should be considered along with PD parameters for drug dosing in critically ill patients with ARC.

CONCLUSION

This review recommends a dosing protocol for some antibiotics to help the appropriate dosing of antibiotics in ARC and decrease the risk of subtherapeutic exposure that may be observed while receiving conventional dosing regimens in critically ill patients with ARC.

Caspofungin Population Pharmacokinetic Analysis in Plasma and Peritoneal Fluid in Septic Patients with Intra-Abdominal Infections: A Prospective Cohort Study

OBJECTIVES

The aim of this study was to report the pharmacokinetics (PK) of caspofungin in plasma and peritoneal fluid and to identify optimal dosing strategies in septic patients with intra-abdominal infections.

METHODS

Eleven patients with secondary peritonitis with septic shock received the standard dosing regimen of caspofungin. Total caspofungin plasma and peritoneal concentrations were subject to a population PK analysis using Pmetrics^®. Monte Carlo simulations were performed considering the ratio of 24-h total drug exposure above the minimum inhibitory concentration (AUC₂₄/MIC) in plasma and comparing simulated concentrations versus MIC in peritoneal fluid.

RESULTS

Fat-free mass (FFM) was retained in the final model of caspofungin, reporting a total clearance (standard deviation) of 0.78 (0.17) L/h and a central volume of distribution of 9.36 (2.61) L. The peritoneal fluid/plasma ratio of caspofungin was 33% on the first day of therapy (AUC₂₄ 73.92 (21.93) and 26.03 (9.88) mg*h/L for plasma and peritoneal data, respectively). Dosing simulations supported the use of standard dosing regimens for patients with an FFM < 50 kg for the most susceptible candida species (C. albicans and C. glabrata). For higher FFM, a loading dose of 70 or 100 mg, with a maintenance dose of 70 mg, reached AUC₂₄/MIC ratios for these species.

CONCLUSIONS

There is moderate penetration of caspofungin into the peritoneal cavity (33%). For empirical treatment, a dose escalation of 100 mg loading dose on the first day is suggested for higher FFM to ensure adequate concentrations into the abdominal cavity for the most susceptible candida species.

Population Pharmacokinetics of Polymyxin B in Obese Patients for Resistant Gram-Negative Infections

Polymyxin B is an effective but potentially nephrotoxic antibiotic that is commonly used to treat resistant Gram-negative infections. As a weight-based dosing drug, obese patients may be at a high risk of nephrotoxicity. However, the pharmacokinetics and dosing recommendations for this population are currently lacking. This study aimed to describe the polymyxin B population pharmacokinetics and to evaluate pharmacokinetic/pharmacodynamics (PK/PD) target attainment for obese patients. This study included 26 patients (body mass index, BMI >30) who received polymyxin B for ≥3 days. The total body weight (TBW) ranged from 75 to 125 kg, and the BMI ranged from 30.04 to 40.35. A two-compartment model adequately described the data using Phoenix NLME software. Monte Carlo simulation was used to assess polymyxin B exposure and the probability of target attainment (PTA). As a result, body weight had no significant effect on polymyxin B pharmacokinetics. According to model-based simulation, adjusted body weight (ABW)-based regimens had a high probability of achieving optimal exposure with minimal toxicity risk by comparing TBW and ideal body weight (IBW)-based regimens. The fixed dose of 125 mg or 150 mg q12h had a high toxicity risk. PTA results showed that TBW, IBW, and ABW-based regimens had similar PTA values. Therefore, for obese patients, ABW-based regimens but with a daily dose <250 mg have a high likelihood of achieving an AUC_ss,24h of 50-100 mg h/L and attaining PK/PD targets with the MIC ≤0.5 mg/L.

Impact of a hospital-wide computerised approach to optimise the quality of antimicrobial prescriptions in patients with severe obesity: a quasi-experimental study

Background

Rates of adherence to available recommendations for dose adjustments in patients with severe obesity are generally low. Hence, antimicrobials are often underdosed in these patients. Antimicrobial stewardship programmes can improve the use of antimicrobials in hospitalised patients. The aim of the study was to analyse the impact of an antimicrobial stewardship programme based on a computerised clinical decision support system for optimal dosing and antimicrobial use in inpatients with severe obesity.

Methods

This quasi-experimental retrospective study using interrupted time series was conducted in an academic centre in Canada from August 2008 to June 2018. The Antimicrobial Prescription Surveillance System was implemented in August 2010 (intervention 1) and specific rules targeting patients with class III obesity (body mass index ≥ 40 kg/m²) were added in June 2014 (intervention 2). Data were collected from all hospitalised adults receiving antimicrobials which required dose adjustment for severe obesity and were stratified by body mass index. Segmented regression analysis of interrupted time series was used to evaluate the impact of the Antimicrobial Prescription Surveillance System on the proportion of inappropriate days of therapy according to posology and on antimicrobial consumption.

Results

Overall, 65 205 antimicrobial prescriptions (68% non-obese, 25% class I-II obesity, and 7% class III obesity) were analysed. In patients with class III obesity, the intervention was associated with a decrease in the proportion of inappropriate days of therapy (trend after the first intervention, −0.8% per 2-month period [95% CI −1.1 to −0.5], p < 0.001; intercept, 11.3% [95% CI 8.2 to 14.5], p < 0.001), which led to a reduction of 35% over an eight-year period (from pre-intervention level of 19.1%). Intervention 1 resulted in a downward trend in antimicrobial consumption, followed by an increasing trend after intervention 2. In these patients, the most frequent interventions made by pharmacists targeted posology (46%).

Conclusions

Antimicrobial Prescription Surveillance System had a positive impact on dosing optimisation and antimicrobial consumption in patients with class III obesity. Improving antimicrobial prescriptions in these patients is important because suboptimal dosing could be associated with unfavourable outcomes.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-021-06682-8.

Pharmacokinetics of Ceftazidime in Children and Adolescents with Obesity

PURPOSE

The aim of this study was to evaluate ceftazidime pharmacokinetics (PK) in a cohort that includes a predominate number of children and adolescents with obesity and assess the efficacy of competing dosing strategies.

METHODS

A population PK model was developed using opportunistically collected plasma samples. For each dosing strategy, model-based probability of target attainment (PTA) estimates were computed for study participants using empirical Bayes estimates. In addition, the effects of body size and renal function on PTA were evaluated using stochastic model simulations with virtually generated subjects.

RESULTS

Twenty-nine participants, 24 of whom were obese, contributed data towards the analysis. The median (range) age, body weight, and body mass index of participants were 12.2 years (2.3-20.6), 59.2 kg (8.4-121), and 25.2 kg/m2 (13.8-42.9), respectively. Administration of 50 mg/kg intravenously (IV) every 8 hours (q8h; max 6 g/day) or 40 mg/kg IV q6h (max 6 g/day) resulted in PTA values of ≥ 90% (minimum inhibitory concentration 8 mg/L) for the subset of obese participants with estimated glomerular filtration rates (GFR) ≥ ~ 80 mL/min/1.73 m2. However, for both regimens, stochastic model simulations denoted lower PTA values (< 90%) with increasing body weight for virtual subjects with GFR ≥ 120 mL/min/1.73 m2. Alternatively, permitting for a maximum daily dose of 8 g/day using a 40 mg/kg IV q6h regimen provided PTA values that were near or above target (90%) for virtual subjects between 10 to 120 kg with GFR ≥ 80 mL/min/1.73 m2.

CONCLUSION

Our analysis suggests administration of 40 mg/kg IV q6h (max 8 g/day) maximizes PTA in children and adolescents with obesity and GFR ≥ 80 mL/min/1.73 m2.

TRIAL REGISTRATION

Clinicaltrials.gov Identifier: NCT01431326.

Similar Piperacillin/Tazobactam Target Attainment in Obese versus Nonobese Patients despite Differences in Interstitial Tissue Fluid Pharmacokinetics

Precision dosing of piperacillin/tazobactam in obese patients is compromised by sparse information on target-site exposure. We aimed to evaluate the appropriateness of current and alternative piperacillin/tazobactam dosages in obese and nonobese patients. Based on a prospective, controlled clinical trial in 30 surgery patients (15 obese/15 nonobese; 0.5-h infusion of 4 g/0.5 g piperacillin/tazobactam), piperacillin pharmacokinetics were characterized in plasma and at target-site (interstitial fluid of subcutaneous adipose tissue) via population analysis. Thereafter, multiple 3-4-times daily piperacillin/tazobactam short-term/prolonged (recommended by EUCAST) and continuous infusions were evaluated by simulation. Adequacy of therapy was assessed by probability of pharmacokinetic/pharmacodynamic target-attainment (PTA ≥ 90%) based on time unbound piperacillin concentrations exceed the minimum inhibitory concentration (MIC) during 24 h (%fT>MIC). Lower piperacillin target-site maximum concentrations in obese versus nonobese patients were explained by the impact of lean (approximately two thirds) and fat body mass (approximately one third) on volume of distribution. Simulated steady-state concentrations were 1.43-times, 95%CI = (1.27; 1.61), higher in plasma versus target-site, supporting targets of %fT>2×MIC instead of %fT>4×MIC during continuous infusion to avoid target-site concentrations constantly below MIC. In all obesity and renally impairment/hyperfiltration stages, at MIC = 16 mg/L, adequate PTA required prolonged (thrice-daily 4 g/0.5 g over 3.0 h at %fT>MIC = 50) or continuous infusions (24 g/3 g over 24 h following loading dose at %fT>MIC = 98) of piperacillin/tazobactam.

No Time Dependence of Ciprofloxacin Pharmacokinetics in Critically Ill Adults: Comparison of Individual and Population Analyses

The aim of this prospective PK study was to evaluate the pharmacokinetics of ciprofloxacin dosed within the first 36 h (early phase) and after 3 days of treatment (delayed phase) using individual and population PK analysis. The secondary aim of the study was to evaluate possible dosing implications of the observed PK differences between early and delayed phases to achieve a PK/PD target for ciprofloxacin of AUC₂₄/MIC ≥ 125. Blood concentrations of ciprofloxacin (1 and 4 h after dose and trough) were monitored in critically ill adults in the early and delayed phases of the treatment. Individual and population PK analyses were performed. Complete concentration-time profiles in the early phase, delayed phase, and both phases were obtained from 29, 15, and 14 patients, respectively. No systematic changes in ciprofloxacin PK parameters between the early and delayed phases were observed, although variability was higher at the early phase. Both individual and population analyses provided similar results. Simulations showed that after standard dosing, it is practically impossible to reach the recommended ciprofloxacin PK/PD target (AUC/MIC ≥ 125) for pathogens with MIC ≥ 0.5 mg/L. A dosing nomogram utilizing patients’ creatinine clearance and MIC values was constructed. Both individual and population analyses provided similar results. Therapeutic drug monitoring should be implemented to safeguard the optimal ciprofloxacin exposure.

Continuous Infusion of Piperacillin/Tazobactam and Meropenem in ICU Patients Without Renal Dysfunction: Are Patients at Risk of Underexposure?

BACKGROUND AND OBJECTIVES

Morbidity and mortality from serious infections are common in intensive care units (ICUs). The appropriateness of the antibiotic treatment is essential to combat sepsis. We aimed to evaluate pharmacokinetic/pharmacodynamic target attainment of meropenem and piperacillin/tazobactam administered at standard total daily dose as continuous infusion in critically ill patients without renal dysfunction and to identify risk factors of non-pharmacokinetic/pharmacodynamic target attainment.

RESULTS

We included 118 patients (149 concentrations), 47% had microorganism isolation. Minimum inhibitory concentration (MIC) [median (interquartile range, IQR) values in isolated pathogens were: meropenem: 0.05 (0.02-0.12) mg/l; piperacillin: 3 (1-4) mg/l]. Pharmacokinetic/pharmacodynamic target attainments (100%fC_ss≥1xMIC, 100%fC_ss≥4xMIC and 100%fC_{ss ≥ 8xMIC}, respectively) were: 100%, 96.15%, 96.15% (meropenem) and 95.56%, 91.11%, 62.22% (piperacillin) for actual MIC; 98.11%, 71.70%, 47.17% (meropenem, MIC 2 mg/l), 95.83%, 44.79%, 6.25% (piperacillin, MIC 8 mg/l), 83.33%, 6.25%, 1.04% (piperacillin, MIC 16 mg/l) for EUCAST breakpoint of Enterobacteriaceae spp. and Pseudomonas spp. Multivariable linear analysis identified creatinine clearance (CrCL) as a predictive factor of free antibiotic concentrations (fC_ss) of both therapies (meropenem [β = - 0.01 (95% CI - 0.02 to - 0.0; p = 0.043)] and piperacillin [β = - 0.01 (95% CI - 0.02 to 0.01, p < 0.001)]). Neurocritical status was associated with lower piperacillin fC_ss [β = - 0.36 (95% CI - 0.61 to - 0.11; p = 0.005)].

CONCLUSION

Standard total daily dose of meropenem allowed achieving pharmacokinetic/pharmacodynamic target attainments in ICU patients without renal dysfunction. Higher doses of piperacillin/tazobactam would be needed to cover microorganisms with MIC > 8 mg/l. CrCL was the most powerful factor predictive of fC_ss in both therapies.

Continuous versus intermittent infusion of cefotaxime in critically ill patients: a randomized controlled trial comparing plasma concentrations

BACKGROUND

In critical care patients, reaching optimal β-lactam concentrations poses challenges, as infections are caused more often by microorganisms associated with higher MICs, and critically ill patients typically have an unpredictable pharmacokinetic/pharmacodynamic profile. Conventional intermittent dosing frequently yields inadequate drug concentrations, while continuous dosing might result in better target attainment. Few studies address cefotaxime concentrations in this population.

OBJECTIVES

To assess total and unbound serum levels of cefotaxime and an active metabolite, desacetylcefotaxime, in critically ill patients treated with either continuously or intermittently dosed cefotaxime.

METHODS

Adult critical care patients with indication for treatment with cefotaxime were randomized to treatment with either intermittent dosing (1 g every 6 h) or continuous dosing (4 g/24 h, after a loading dose of 1 g). We defined a preset target of reaching and maintaining a total cefotaxime concentration of 4 mg/L from 1 h after start of treatment. CCMO trial registration number NL50809.042.14, Clinicaltrials.gov NCT02560207.

RESULTS

Twenty-nine and 30 patients, respectively, were included in the continuous dosing group and the intermittent dosing group. A total of 642 samples were available for analysis. In the continuous dosing arm, 89.3% met our preset target, compared with 50% in the intermittent dosing arm. Patients not reaching this target had a significantly higher creatinine clearance on the day of admission.

CONCLUSIONS

These results support the application of a continuous dosing strategy of β-lactams in critical care patients and the practice of therapeutic drug monitoring in a subset of patients with higher renal clearance and need for prolonged treatment for further optimization, where using total cefotaxime concentrations should suffice.

Prolonged Infusion of β-Lactams Decreases Mortality in Patients with Septic Shock: A Retrospective before-and-after Study

Septic shock substantially alters the pharmacokinetic properties of β-lactams with a subsequently high risk of insufficiently low serum concentrations and treatment failure. Considering their pharmacokinetic (PK)/pharmacodynamic (PD) index, prolonged infusions (PI) of β-lactams extend the time that the unbound fraction of the drug remains above the minimal inhibitory concentration MIC (ft _>MIC) and may improve patient survival. The present study is a monocentric, retrospective before-and-after analysis of septic shock patients treated with β-lactams. Patients of the years 2015–2017 received intermittent bolus application whereas patients of 2017–2020 received PI of β-lactams. The primary outcome was mortality at day 30 and 90 after diagnosis of septic shock. Mortality rates in the PI group were significantly lower on day 30 (PI: 41%, n = 119/290 vs. IB: 54.8%, n = 68/114; p = 0.0097) and day 90 (PI: 47.9%, n = 139/290 vs. IB: 62.9%, n = 78/124; p = 0.005). After propensity-score matching, 30- and 90-day mortality remained lower for the PI group (−10%, p = 0.14). PI was further associated with a reduction in the duration of invasive ventilation and a stronger decrease in SOFA scores within a 14 day-observation period. PI of β-lactams was associated with a significant reduction of mortality in patients with septic shock and may have beneficial effects on invasive ventilation and recovery from sepsis-related organ failure.

Pharmacokinetics and Pharmacodynamics of Meropenem by Extended or Continuous Infusion in Low Body Weight Critically Ill Patients

Background: Pathophysiological changes such as extreme body weights in critically ill patients with severe infections may alter the pharmacokinetics (PK) of antimicrobials, leading to treatment failure or toxicity. There are almost no PK data on meropenem in critically ill patients with low body weight (LwBW) and therefore information is lacking on the most appropriate dosing regimens, especially when administered by extended infusion. Objectives: To assess if the current administered doses of meropenem could lead to supratherapeutic concentrations in LwBW patients and to identify the factors independently associated with overexposure. Methods: A matched case-control 1:1 study of surgical critically ill patients treated with meropenem administered by extended or continuous infusion and undergoing therapeutic drug monitoring was conducted. Cases (patients with LwBW (body mass index (BMI) < 18.5 kg/m²)) were matched with normal body weight controls (NBW) (patients with BMI ≥ 18.5 kg/m² and ≤30 kg/m²)) by age, gender, baseline renal function and severity status (APACHE II score). A 100% fT > MIC was considered an optimal pharmacokinetic/pharmacodynamic (PK/PD) target and 100% fT > 10 × MIC as supratherapeutic exposure. Results: Thirty-six patients (18 cases and 18 controls) were included (median (range) age, 57.5 (26–75) years; 20 (55.6% male)). Meropenem was administered by 6 h (extended) or 8 h (continuous) infusion at a median (range) daily dose of 5 (1–6) g/day. Similar median meropenem trough plasma concentrations (Cmin,ss), measured pre-dose on day three to four of treatment) were observed in the two groups (19.9 (22.2) mg/L vs 22.4 (25.8) mg/L, p > 0.999). No differences in the proportion of patients with an optimal or a supratherapeutic PKPD target between cases and controls were observed. A baseline estimated glomerular filtration rate (eGFR) < 90 mL/min was the only factor independently associated with a supratherapeutic PK/PD target. Conclusions: LwBW seems not to be a risk factor for achieving a supratherapeutic PK/PD target in critically ill patients receiving meropenem at standard doses by extended or continuous infusion.

Towards precision medicine: Therapeutic drug monitoring-guided dosing of vancomycin and β-lactam antibiotics to maximize effectiveness and minimize toxicity

PURPOSE

The goal of this review is to explore the role of antimicrobial therapeutic drug monitoring (TDM), especially in critically ill, obese, and older adults, with a specific focus on β-lactams and vancomycin.

SUMMARY

The continued rise of antimicrobial resistance prompts the need to optimize antimicrobial dosing. The aim of TDM is to individualize antimicrobial dosing to achieve antibiotic exposures associated with improved patient outcomes. Initially, TDM was developed to minimize adverse effects during use of narrow therapeutic index agents. Today, patient and organism complexity are expanding the need for precision dosing through TDM services. Alterations of pharmacokinetics and pharmacodynamics (PK/PD) in the critically ill, obese, and older adult populations, in conjunction with declining organism susceptibility, complicate attainment of therapeutic targets. Over the last decade, antimicrobial TDM has expanded with the emergence of literature supporting β-lactam TDM and a shift from monitoring vancomycin trough concentrations to monitoring of the ratio of area under the concentration (AUC) curve to minimum inhibitory concentration (MIC). PK/PD experts should be at the forefront of implementing precision dosing practices.

CONCLUSION

Precision dosing through TDM is expanding and is especially important in populations with altered PK/PD, including critically ill, obese, and older adults. Due to wide PK/PD variability in these populations, TDM is vital to maximize antimicrobial effectiveness and decrease adverse event rates. However, there is still a need for studies connecting TDM to patient outcomes. Providing patient-specific care through β-lactam TDM and transitioning to vancomycin AUC/MIC monitoring may be challenging, but with experts at the forefront of this initiative, PK-based optimization of antimicrobial therapy can be achieved.

Impact of body size on first-line Helicobacter pylori eradication success using vonoprazan and amoxicillin dual therapy

BACKGROUND

As a first-line therapy for Helicobacter pylori, dual therapy with vonoprazan and amoxicillin (VA-dual) provides an eradication rate similar to that of vonoprazan-based triple therapy. As the factors associated with the eradication rate of H. pylori with VA-dual are unknown,we investigated them in this study.

MATERIALS AND METHODS

Overall, 163 patients diagnosed with H. pylori infection received VA-dual (vonoprazan 20 mg twice daily and amoxicillin 750 mg twice daily for 7 d). The association between successful H. pylori eradication and the following patient clinical factors was analyzed: sex, age, height, weight, body surface area (BSA), body mass index (BMI), history of early gastric carcinoma and peptic ulcer, comorbidity of cirrhosis, alcohol consumption habit, smoking habit, common use of proton pump inhibitors, and concomitant use of drugs that are substratesof cytochrome P450 (CYP) 3A4. The association between post-eradication adverse events and clinical factors was analyzed retrospectively.

RESULTS

Successful H. pylori eradication was associated with a lower BSA (eradication rate: 90.8% in patients with BSA <1.723 vs. 79.6% in those with BSA ≥1.723; p = 0.045). The incidence of adverse events was higher in women than in men (adverse events: 40.0% in women vs. 19.4% in men; p = 0.004).

CONCLUSIONS

Successful H. pylori eradication with VA-dual was associated with the small body size of patients. This therapy may have to be adjusted per body size.

A narrative review of predictors for β-lactam antibiotic exposure during empirical treatment in critically ill patients

INTRODUCTION

: Emerging studies suggest that antibiotic pharmacokinetics (PK) are difficult to predict in critically ill patients. The high intra- and inter-patient PK variability makes it challenging to accurately predict the appropriate dosage required for a given patient. Identifying patients at risk could help clinicians to consider more individualized dosing regimens and perform therapeutic drug monitoring. We provide an overview of relevant predictors associated with target (non-)attainment of β-lactam antibiotics in critically ill patients.

AREAS COVERED

: This narrative review summarizes patient and clinical characteristics that can help to predict the attainment of target serum concentrations and to provide guidance on antimicrobial dose optimization. Literature was searched using Embase and Medline database, focusing on β-lactam antibiotics in critically ill patients.

EXPERT OPINION

: Adequate concentration attainment can be anticipated in critically ill patients prior to initiating empiric β-lactam antibiotic therapy based on readily available demographic and clinical factors. Male gender, younger age, and augmented renal clearance were the most significant predictors for target non-attainment and should be considered in further investigations to develop dosing algorithms for optimal β-lactam therapy.

Evaluation of Linezolid Pharmacokinetics in Critically Ill Obese Patients with Severe Skin and Soft Tissue Infections

Linezolid standard dosing is fixed at 600 mg every 12 h (q12h) for adults. Literature suggests critically ill, obese patients require higher doses. The study aim is 2-fold: (i) to describe linezolid pharmacokinetics (PK), and (ii) to evaluate if PK/pharmacodynamic (PD) target attainment is achieved with standard dosing in critically ill, obese patients with severe skin and soft tissue infections (SSTIs). Adult patients with a body mass index (BMI) of ≥30 kg/m² and receiving intravenous (i.v.) linezolid from August 2018 to April 2019 were eligible for consent in this prospective study. Severe SSTIs were defined as necrotizing fasciitis, myonecrosis, or SSTI with sepsis syndrome. Four blood samples were collected at steady state at 1, 3, 5 h postinfusion and as a trough. Target attainment was defined as achieving area under the concentration-time curve from 0 to 24 h to MIC (AUC_0-24h/MIC) of ≥100 h*mg/liter. Monte Carlo simulations were used to determine the probability of target attainment (PTA). Eleven patients were included in the study. The median BMI was 45.7 kg/m², and median total body weight (TBW) was 136.0 kg. Seven patients received standard linezolid doses, and four received 600 mg q8h. A one-compartment model described linezolid PK. Based on AUC_0-24h/MIC targets, for noncirrhotic patients at 140 kg, the PTA with standard linezolid doses was 100%, 98.8%, 34.1%, and 0% for MICs of 0.5, 1, 2, and 4 mg/liter, respectively. In conclusion, target attainment of ≥90% is not achieved with standard linezolid doses for noncirrhotic patients ≥140 kg with MICs of ≥2 mg/liter. This study adds to accumulating evidence that standard linezolid doses may not be adequate for all patients.

Meropenem Plasma and Interstitial Soft Tissue Concentrations in Obese and Nonobese Patients-A Controlled Clinical Trial

BACKGROUND

This controlled clinical study aimed to investigate the impact of obesity on plasma and tissue pharmacokinetics of meropenem.

METHODS

Obese (body mass index (BMI) ≥ 35 kg/m²) and age-/sex-matched nonobese (18.5 kg/m² ≥ BMI ≤ 30 kg/m²) surgical patients received a short-term infusion of 1000-mg meropenem. Concentrations were determined via high performance liquid chromatography-ultraviolet (HPLC-UV) in the plasma and microdialysate from the interstitial fluid (ISF) of subcutaneous tissue up to eight h after dosing. An analysis was performed in the plasma and ISF by noncompartmental methods.

RESULTS

The maximum plasma concentrations in 15 obese (BMI 49 ± 11 kg/m²) and 15 nonobese (BMI 24 ± 2 kg/m²) patients were 54.0 vs. 63.9 mg/L (95% CI for difference: -18.3 to -3.5). The volume of distribution was 22.4 vs. 17.6 L, (2.6-9.1), but the clearance was comparable (12.5 vs. 11.1 L/h, -1.4 to 3.1), leading to a longer half-life (1.52 vs. 1.31 h, 0.05-0.37) and fairly similar area under the curve (AUC)_8h (78.7 vs. 89.2 mg*h/L, -21.4 to 8.6). In the ISF, the maximum concentrations differed significantly (12.6 vs. 18.6 L, -16.8 to -0.8) but not the AUC_8h (28.5 vs. 42.0 mg*h/L, -33.9 to 5.4). Time above the MIC (T > MIC) in the plasma and ISF did not differ significantly for MICs of 0.25-8 mg/L.

CONCLUSIONS

In morbidly obese patients, meropenem has lower maximum concentrations and higher volumes of distribution. However, due to the slightly longer half-life, obesity has no influence on the T > MIC, so dose adjustments for obesity seem unnecessary.

Is Antimicrobial Dosing Adjustment Associated with Better Outcomes in Patients with Severe Obesity and Bloodstream Infections? An Exploratory Study

The impact of adjusted treatment on clinical outcomes in patients with severe obesity is unclear. This study included adults with severe obesity admitted for bloodstream infections between 2005 and 2015. The patients were grouped according to the percentage of the appropriateness of the dosage of their antimicrobial treatment: 80–100% = good, 20–79% = moderate, and 0–19% = poor. The association between antimicrobial adjustment and a composite of unfavourable outcomes [intensive care unit stay ≥72 h, duration of sepsis >3 days, length of stay ≥7 days or all-cause 30-day mortality] was assessed using logistic regression. Of 110 included episodes, the adjustment was rated good in 47 (43%) episodes, moderate in 31 (28%), and poor in 32 (29%). Older age, Pitt bacteremia score ≥2, sepsis on day 1, and infection site were independent risk factors for unfavourable outcomes. The level of appropriateness was not associated with unfavourable outcomes. The number of antimicrobials, consultation with an infectious disease specialist, blood urea nitrogen 7–10.9 mmol/L, and hemodialysis were significantly associated with adjusted antimicrobial dosing. While the severity of the infection had a substantial impact on the measured outcomes, we did not find an association between dosing optimization and better outcomes.

Population Pharmacokinetics of Imipenem in Critically Ill Patients: A Parametric and Nonparametric Model Converge on CKD-EPI Estimated Glomerular Filtration Rate as an Impactful Covariate

BACKGROUND

Population pharmacokinetic (popPK) models for antibiotics are used to improve dosing strategies and individualize dosing by therapeutic drug monitoring. Little is known about the differences in results of parametric versus nonparametric popPK models and their potential consequences in clinical practice. We developed both parametric and nonparametric models of imipenem using data from critically ill patients and compared their results.

METHODS

Twenty-six critically ill patients treated with intravenous imipenem/cilastatin were included in this study. Median estimated glomerular filtration rate (eGFR) measured by the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation was 116 mL/min/1.73 m2 (interquartile range 104-124) at inclusion. The usual dosing regimen was 500 mg/500 mg four times daily. On average, five imipenem levels per patient (138 levels in total) were drawn as peak, intermediate, and trough levels. Imipenem concentration-time profiles were analyzed using parametric (NONMEM 7.2) and nonparametric (Pmetrics 1.5.2) popPK software.

RESULTS

For both methods, data were best described by a model with two distribution compartments and the CKD-EPI eGFR equation unadjusted for body surface area as a covariate on the elimination rate constant (Ke). The parametric population parameter estimates were Ke 0.637 h-1 (between-subject variability [BSV]: 19.0% coefficient of variation [CV]) and central distribution volume (Vc) 29.6 L (without BSV). The nonparametric values were Ke 0.681 h-1 (34.0% CV) and Vc 31.1 L (42.6% CV).

CONCLUSIONS

Both models described imipenem popPK well; the parameter estimates were comparable and the included covariate was identical. However, estimated BSV was higher in the nonparametric model. This may have consequences for estimated exposure during dosing simulations and should be further investigated in simulation studies.

Controversies in Perioperative Antimicrobial Prophylaxis

Although clinical guidelines for antibiotic prophylaxis across a wide array of surgical procedures have been proposed by multidisciplinary groups of physicians and pharmacists, clinicians often deviate from recommendations. This is particularly true when recommendations are based on weak data or expert opinion. The goal of this review is to highlight certain common but controversial topics in perioperative prophylaxis and to focus on the data that does exist for the recommendations being made.

Antimicrobial therapeutic drug monitoring in critically ill adult patients: a Position Paper

Purpose

This Position Paper aims to review and discuss the available data on therapeutic drug monitoring (TDM) of antibacterials, antifungals and antivirals in critically ill adult patients in the intensive care unit (ICU). This Position Paper also provides a practical guide on how TDM can be applied in routine clinical practice to improve therapeutic outcomes in critically ill adult patients.

Methods

Literature review and analysis were performed by Panel Members nominated by the endorsing organisations, European Society of Intensive Care Medicine (ESICM), Pharmacokinetic/Pharmacodynamic and Critically Ill Patient Study Groups of European Society of Clinical Microbiology and Infectious Diseases (ESCMID), International Association for Therapeutic Drug Monitoring and Clinical Toxicology (IATDMCT) and International Society of Antimicrobial Chemotherapy (ISAC). Panel members made recommendations for whether TDM should be applied clinically for different antimicrobials/classes.

Results

TDM-guided dosing has been shown to be clinically beneficial for aminoglycosides, voriconazole and ribavirin. For most common antibiotics and antifungals in the ICU, a clear therapeutic range has been established, and for these agents, routine TDM in critically ill patients appears meritorious. For the antivirals, research is needed to identify therapeutic targets and determine whether antiviral TDM is indeed meritorious in this patient population. The Panel Members recommend routine TDM to be performed for aminoglycosides, beta-lactam antibiotics, linezolid, teicoplanin, vancomycin and voriconazole in critically ill patients.

Conclusion

Although TDM should be the standard of care for most antimicrobials in every ICU, important barriers need to be addressed before routine TDM can be widely employed worldwide.

Electronic supplementary material

The online version of this article (10.1007/s00134-020-06050-1) contains supplementary material, which is available to authorized users.

Linezolid Concentrations in Plasma and Subcutaneous Tissue are Reduced in Obese Patients, Resulting in a Higher Risk of Underdosing in Critically Ill Patients: A Controlled Clinical Pharmacokinetic Study

Background: Linezolid is used for the treatment of soft tissue infections in critically ill patients. However, data for characterizing the pharmacokinetics (PK) and assessing whether effective concentrations are reached at the target site are lacking. We hypothesized that current dosing regimens do not lead to effective concentrations in the plasma and interstitial fluid (ISF) of subcutaneous tissue in obese patients. Methods: As a controlled clinical model, critically ill obese and non-obese patients undergoing intra-abdominal surgery received 600 mg linezolid as a single infusion. Concentrations in the plasma and microdialysate from the ISF of subcutaneous tissue were determined up to 8 h after dosing. Pharmacokinetic analysis was performed by non-compartmental methods. As a therapeutic target, we used fAUC/MIC > 80. Results: Fifteen obese (BMI: 48.7 ± 11.2 kg/m²) and 15 non-obese (23.9 ± 2.1 kg/m²) patients were analyzed. AUC_0–8 in ISF decreased by −1.69 mg*h/L (95% CI: −2.59 to −0.79, p < 0.001) for every 10 kg increase in weight. PK in obese patients were characterized by lower maximal plasma concentrations (median 3.8 vs. 8.3 mg/L, p < 0.001) and a higher volume of distribution (41.0 vs. 30.8 L, p < 0.001), and the therapeutic target was not reached for MIC ≥ 1 mg/L in ISF and ≥ 2 mg/L in plasma. Conclusions: Increasing the weight led to a decrease of linezolid concentrations in the plasma and subcutaneous tissue. The current dosing regimen does not seem to produce sufficient concentrations to kill bacteria with MIC ≥ 2 mg/L, especially as empirical antimicrobial therapy in critically ill obese patients.

Therapeutic Drug Monitoring of Levoffoxacin in an Obese Adolescent: A Case Report

OBJECTIVES

To describe the pharmacokinetics of levofloxacin in an obese adolescent patient in the pediatric intensive care unit.

METHODS

A single-patient medical record review was conducted.

RESULTS

A 168-kg, 15-year-old female with past medical history of Prader-Willi syndrome and asthma initially presented with respiratory distress secondary to asthma exacerbation. She failed non-invasive ventilation and was subsequently intubated for respiratory failure and progressed to high-frequency oscillatory ventilation. On hospital day 1 (HD 1) an infectious workup was begun because of a fever, worsening clinical status, and initiation of vasopressors and an empiric antimicrobial regimen of cefepime and clindamycin. The urine culture subsequently grew Escherichia coli and the respiratory culture grew Pseudomonas aeruginosa. She continued to be febrile, which was thought to be due to an intra-abdominal abscess. On HD 14, the antimicrobial regimen was changed to levofloxacin because of continued fevers and no significant clinical improvement. Levofloxacin was initiated at 1000 mg IV every 24 hours. Levofloxacin serum levels were obtained at 0.5, 3.5, and 11.5 hours after infusion, which were 8.61, 5.76, and 2.7 mg/L, respectively. These concentrations translated into a peak level of 8.79 mg/L, a half-life of 6.4 hours, and an AUC of 80 mg·hr/L, which are discordant from the expected peak of 16 mg/L, a half-life of 8 hours, and an AUC of 120 mg·hr/L. Based on these values, the levofloxacin regimen was adjusted to 1000 mg IV every 12 hours, and repeat levels 0.5, 3.5, and 11.5 hours after infusion were 9.91, 6.56, and 3.27 mg/L, respectively, corresponding to a peak of 10.5 mg/L, a half-life of 5.18 hours, and an AUC of 200 mg·hr/L. After the adjustment in levofloxacin regimen, she became afebrile, WBC resolution and improvement in her overall clinical status, and she received a total duration for levofloxacin of 21 days.

CONCLUSION

A levofloxacin regimen of 1000 mg IV every 12 hours was successful in providing for an appropriate AUC exposure and was associated with a successful clinical outcome in this morbidly obese adolescent.