Optimizing dosing of antibiotics in critically ill patients

Determination of meropenem in capillary plasma microsamples using LC-MS/MS

Background: The measurement of meropenem plasma concentrations is employed for dosing regimen individualization. The aim of this study was to develop and validate a LC-MS/MS assay for quantification of meropenem in capillary plasma microsamples. Methods: Samples were prepared by protein precipitation with acetonitrile, followed by clean-up with dichloromethane. The method was validated and applied to 12 paired samples of venous and capillary plasma. Results: The method was linear in the range of 0.5-50 μg/ml. Matrix effects were minimal. Inter- and intra-assay were 3.8-7.9% and 2.7-5.5%, respectively, while accuracy was 91.7-100.6%. Concentrations in capillary and venous plasma were highly correlated. Conclusion: An assay for the quantification of meropenem in capillary plasma microsamples was fully validated, showing potential for clinical application.

A rapid and simple HPLC-MS/MS method for the therapeutic drug monitoring of six special-grade antimicrobials in pediatric patients

Meropenem, linezolid, fluconazole, voriconazole, posaconazole, and vancomycin are six important antimicrobials used for severe infections in critically ill patients listed in special-grade antimicrobials in China. The six antimicrobials' highly variable pharmacodynamics and pharmacokinetics in critically ill pediatric patients present significant challenges to clinicians in ensuring optimal therapeutic targets. Therefore, therapeutic drug monitoring of these antimicrobials in human plasma is necessary to obtain their plasma concentration. A rapid, simple, and sample-saving high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method was developed, which could simultaneously determine all six antimicrobials. It required only 10 μL of plasma and a one-step protein precipitation process. Chromatographic separation was achieved on a reversed-phase column (C18, 30 × 2.1 mm, 2.6 μm) via gradient elution using water and acetonitrile containing 0.1 % formic acid as mobile phase. The injection volume was 2 μL, and the total run time was only 2.5 min. Detection was done using a Triple Quad™ 4500MD tandem mass spectrometer coupled with an electrospray ionization (ESI) source in positive mode. The calibration curves ranged from 0.5 to 64 μg/mL for meropenem and fluconazole, 0.2-25.6 μg/mL for linezolid and voriconazole, 0.1-12.8 μg/mL for posaconazole and 1-128 μg/mL for vancomycin, with the coefficients of correlation all greater than 0.996. Furthermore, the method was validated rigorously according to the European Medicines Agency (EMA) guidelines, demonstrating excellent accuracy (from 93.0 % to 110.6 %) and precision (from 2.0 % to 12.8 %). Moreover, its applicability to various matrices (including serum, hemolytic plasma, and hyperlipidemic plasma) was evaluated. Thus, this method was successfully applied to routine therapeutic drug monitoring for critically ill pediatric patients and other patients in need.

Antimicrobial Pharmacokinetics and Pharmacodynamics in Critical Care: Adjusting the Dose in Extracorporeal Circulation and to Prevent the Genesis of Multiresistant Bacteria

Critically ill patients suffering from severe infections are prone to pathophysiological pharmacokinetic changes that are frequently associated with inadequate antibiotic serum concentrations. Minimum inhibitory concentrations (MICs) of the causative pathogens tend to be higher in intensive care units. Both pharmacokinetic changes and high antibiotic resistance likely jeopardize the efficacy of treatment. The use of extracorporeal circulation devices to support hemodynamic, respiratory, or renal failure enables pharmacokinetic changes and makes it even more difficult to achieve an adequate antibiotic dose. Besides a clinical response, antibiotic pharmacokinetic optimization is important to reduce the selection of strains resistant to common antibiotics. In this review, we summarize the present knowledge regarding pharmacokinetic changes in critically ill patients and we discuss the effects of extra-corporeal devices on antibiotic treatment together with potential solutions.

Antimicrobial stewardship programs in the Intensive Care Unit in patients with infections caused by multidrug-resistant Gram-negative bacilli

Antimicrobial stewardship programs (ASPs) have been shown to be effective and safe, contributing to reducing and adjusting antimicrobial use in clinical practice. Such programs not only reduce antibiotic selection pressure and therefore the selection of multidrug-resistant strains, but also reduce the potential deleterious effects for individual patients and even improve the prognosis by adjusting the choice of drug and dosage, and lessening the risk of adverse effects and interactions. Gram-negative bacilli (GNB), particularly multidrug-resistant strains (MDR-GNB), represent the main infectious problem in the Intensive Care Unit (ICU), and are therefore a target for ASPs. The present review provides an update on the relationship between ASPs and MDR-GNB.

LCMS/MS-based multiplex antibacterial platform for therapeutic drug monitoring in intensive care unit patients

Empirically prescribed standard dosing regimens of antibacterial agents may result in insufficient or excess plasma concentrations with persistently poor clinical outcomes, especially for patients in intensive care units (ICUs). Therapeutic drug monitoring (TDM) of antibacterial agents can guide dose adjustments to benefit patients. In this study, we developed a robust, sensitive, and simple liquid chromatography-tandem mass spectrometry (LC-MS/MS) platform for the quantification of 14 antibacterial and antifungal agents (beta-lactams piperacillin, cefoperazone, and meropenem; beta-lactamase inhibitors tazobactam and sulbactam; antifungal agents fluconazole, caspofungin, posaconazole, and voriconazole; and daptomycin, vancomycin, teicoplanin, linezolid, and tigecycline) that can be used for patients with severe infection. This assay requires only 100 µL of serum with rapid protein precipitation. Chromatographic analysis was performed using a Waters Acquity UPLC C8 column. Three stable isotope-labeled antibacterial agents and one analogue were used as internal standards. Calibration curves ranged from 0.1-100 μg/mL, 0.1-50 μg/mL, and 0.3-100 μg/mL for different drugs, and all correlation coefficients were greater than 0.9085. Intra- and inter-day imprecision and inaccuracy values were below 15%. After validation, this new method was successfully employed for TDM in routine practice.

Preanalytical Stability of Flucloxacillin, Piperacillin, Tazobactam, Meropenem, Cefalexin, Cefazolin, and Ceftazidime in Therapeutic Drug Monitoring: A Structured Review

BACKGROUND

Therapeutic drug monitoring is increasingly being used to optimize beta-lactam antibiotic dosing. Because beta-lactams are inherently unstable, confirming preanalytical sample stability is critical for reporting reliable results. This review aimed to summarize the published literature on the preanalytical stability of selected widely prescribed beta-lactams used in therapeutic drug monitoring.

METHODS

The published literature (2010-2020) on the preanalytical stability of flucloxacillin, piperacillin, tazobactam, meropenem, cefalexin, cefazolin, and ceftazidime in human plasma, serum, and whole blood was reviewed. Articles examining preanalytical stability at room temperature, refrigerated, or frozen (-20°C) using liquid chromatography with mass spectrometry or ultraviolet detection were included.

RESULTS

Summarizing the available data allowed for general observations to be made, although data were conflicting in some cases (piperacillin, tazobactam, ceftazidime, and meropenem at room temperature, refrigerated, or -20°C) or limited (cefalexin, cefazolin, and flucloxacillin at -20°C). Overall, with the exception of the more stable cefazolin, preanalytical instability was observed after 6-12 hours at room temperature, 2-3 days when refrigerated, and 1-3 weeks when frozen at -20°C. In all cases, excellent stability was detected at -70°C. Studies focusing on preanalytical stability reported poorer stability than studies investigating stability as part of method validation.

CONCLUSIONS

Based on this review, as general guidance, clinical samples for beta-lactam analysis should be refrigerated and analyzed within 2 days or frozen at -20°C and analyzed within 1 week. For longer storage times, freezing at -70°C was required to ensure sample stability. This review highlights the importance of conducting well-designed preanalytical stability studies on beta-lactams and other potentially unstable drugs under clinically relevant conditions.

Evaluation of 4 quantification methods for monitoring 16 antibiotics and 1 beta-lactamase inhibitor in human serum by high-performance liquid chromatography with tandem mass spectrometry detection

Antibiotic (ATB) prescription in an intensive care unit (ICU) requires continuous monitoring of serum dosages due to the patient's pathophysiological condition. Dosing adjustment is necessary to achieve effective targeted concentrations. Since ICUs routinely use a large number of ATBs, global monitoring needs to be developed. In the present study, we developed a global analytical method for extracting, separating and quantifying the most widely used ATBs in ICUs: amoxicillin, piperacillin, cefazolin, cefepime, cefotaxime, ceftazidime, ceftolozane, ceftriaxone, ertapenem, meropenem, ciprofloxacin, moxifloxacin, levofloxacin, daptomycin, dalbavancin, linezolid and a beta-lactamase inhibitor: tazobactam. To guarantee the robustness of the quantification, we differentiated the 16 ATBs and the beta lactamase inhibitor into 4 pools (ATB1 to ATB4), taking into account prescription frequency in the ICU, the physicochemical properties and the calibration ranges of the ATBs selected. The whole ATB was then separated with two LC columns in reversed phase: Kinetex Polar-C18 100 Å and Polar-RP-80 synergy, in less than 6.5 min. Detection was carried out by electrospray in positive ion mode, by tandem mass spectrometry (LC-MS/MS. The four quantification methods were validated according to the European guidelines on bioanalytical method validation (EMEA guide), after determining the extraction yields, matrix effects, recovery, precision, accuracy, within-run precision and between-run precision. For all analyses, bias is < 15% and is comparable to the literature and LOQs vary from 0.05 mg.L^-1 for ciprofloxacin to 1.00 mg.L^-1 for ceftriaxone and dalbavancin. The stability time of cefepime and piperacillin is 3 hrs and for the other ATBs 6 hrs in serum at room temperature. For long-term stability, freezing at - 80 °C guarantees 3 months of stability for ceftriaxone and dalbavancin and more than 6 months for the other ATBs.

Drug Regimens of Novel Antibiotics in Critically Ill Patients with Varying Renal Functions: A Rapid Review

There is currently an increase in the emergence of multidrug-resistant bacteria (MDR) worldwide, requiring the development of novel antibiotics. However, it is not only the choice of antibiotic that is important in treating an infection; the drug regimen also deserves special attention to avoid underdosing and excessive concentrations. Critically ill patients often have marked variation in renal function, ranging from augmented renal clearance (ARC), defined as a measured creatinine clearance (CrCL) ≥ 130 mL/min*1.73 m², to acute kidney injury (AKI), eventually requiring renal replacement therapy (RRT), which can affect antibiotic exposure. All novel beta-lactam (BLs) and/or beta-lactam/beta-lactamases inhibitors (BL/BLIs) antibiotics have specific pharmacokinetic properties, such as hydrophilicity, low plasma–protein binding, small volume of distribution, low molecular weight, and predominant renal clearance, which require adaptation of dosage regimens in the presence of abnormal renal function or RRT. However, there are limited data on the topic. The aim of this review was therefore to summarize available PK studies on these novel antibiotics performed in patients with ARC or AKI, or requiring RRT, in order to provide a practical approach to guide clinicians in the choice of the best dosage regimens in critically ill patients.

OUP accepted manuscript

Background

Dosing regimens guided by therapeutic drug monitoring (TDM) may be able to improve penicillin exposure in patients, which could result in improved patient health outcomes.

Objectives

This systematic review aims to describe the impact penicillin TDM has on health outcomes, including antimicrobial resistance (AMR).

Methods

Studies measuring penicillins in patient samples that adjusted regimens according to the result, and reported health outcomes were selected. Study bias was assessed according to study type. Included study characteristics were tabulated and described by narrative synthesis.

Results

Three randomized controlled trials (RCTs), 16 cohort studies, and 9 case studies were included. No RCTs showed statistically significant improvements in health outcomes. Five cohort studies showed improvement in at least one health outcome associated with target attainment. However, there was a high risk of bias in all studies for health outcomes. One study assessed the impact of penicillin TDM on AMR and found that improved target attainment was associated with suppression of resistance. No studies found a detrimental effect of penicillin TDM.

Conclusions

There is little evidence to suggest that TDM improves health outcomes, however neither health outcomes nor impact on AMR were adequately addressed. Variations in TDM implementation meant that a meta-analysis was not suitable. Penicillin TDM needs standardization, however there is currently no clear evidence of optimal conditions. Suitably powered studies are required to resolve the ambiguity surrounding the impact of TDM on clinical outcomes, including AMR. Further, standardized protocols and concentration targets need to be identified for TDM to be implemented successfully.

Estimation of the Difference in Colistin Plasma Levels in Critically Ill Patients with Favorable or Unfavorable Clinical Outcomes

In recent decades, antimicrobial resistance (AMR) has led to an increased use of therapeutic alternatives. Among these options, colistin continues to be an option for the treatment of multi-resistant (MDR) Gram-negative bacterial infections. However, due to its high toxicity (nephrotoxicity and neurotoxicity) and narrow therapeutic window, colistin treatment must be utilized carefully. Colistin-treated patients have been observed to have higher mortality due to inadequate therapeutic levels. The objective of this study was to estimate the difference in colistin plasma levels in critically ill patients, and its relationship to favorable or unfavorable clinical outcomes. This prospective observational study was conducted between September 2017 and June 2020 at the Universidad de La Sabana Clinic, in patients who had been treated with colistimethate sodium (CMS) for at least 72 h until day 7 of drug treatment in the critical care unit of a university hospital. There were no statistically significant differences in colistin levels between groups with favorable or unfavorable clinical outcomes (0.16 SD vs. 0.54 SD p-value = 0.167). There was higher mortality in patients with subtherapeutic levels (18% vs. 0%), and additionally, there was a greater rate of renal failure in the group with higher therapeutic levels (50% vs. 20.7%). Due to the loss of power of the study, we were unable to demonstrate a possible difference between colistin levels related to favorable or unfavorable clinical outcomes at day 7. However, we recommend further studies to evaluate the impact of measuring levels in terms of mortality and security.

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.

Pharmacokinetic/pharmacodynamic target attainment in critically ill renal patients on antimicrobial usage: focus on novel beta-lactams and beta lactams/beta-lactamase inhibitors

INTRODUCTION

Several novel beta-lactams (BLs) and/or beta lactams/beta-lactamase inhibitors (BL/BLIs) have been recently developed for the management of multidrug-resistant bacterial infections. Data concerning dose optimization in critically ill patients with altered renal function are scanty.

AREAS COVERED

This article provides a critical reappraisal of pharmacokinetic and clinical issues emerged with novel BLs and/or BL/BLIs in renal critically ill patients. Clinical and pharmacokinetic studies published in English until December 2020 were searched on the PubMed-MEDLINE database.

EXPERT OPINION

Several issues emerged with the use of novel BLs and/or BL/BLIs in critically ill renal patients. Suboptimal clinical response rate with ceftazidime-avibactam and ceftolozane-tazobactam was reported in phase II-III trials in patients with moderate kidney injury; data on patients undergoing renal replacement therapy are limited to some case reports; dose adjustment in augmented renal clearance is provided only for cefiderocol. Implementation of altered dosing strategies (prolonged infusion and/or higher dosage) coupled with adaptive real-time therapeutic drug monitoring could represent the most effective approach in warranting optimal pharmacokinetic/pharmacodynamic targets with novel BLs and/or BL/BLIs in challenging scenarios, thus minimizing the risk of clinical failure and/or of resistance selection.

Systematic review: the bioavailability of orally administered antibiotics during the initial phase of a systemic infection in non-ICU patients

Background

The systemic response to an infection might influence the pharmacokinetics of antibiotics. To evaluate the desired possibility of an earlier (< 24 h) IV-to-oral switch therapy in febrile non-ICU, hospitalized patients, a systematic review was performed to assess the effect of the initial phase of a systemic infection on the bioavailability of orally administered antibiotics in such patients.

Methods

An electronic search was conducted in MEDLINE and Embase up to July 2020. Studies were selected when outcome data were collected during the initial stage of a febrile disease. Outcome data were (maximum) serum concentrations, time of achieving maximum serum concentration, and the area-under-the-plasma-concentration-time curve or bioavailability of orally administered antibiotics. Risk of bias was assessed.

Results

We identified 9 studies on 6 antibiotics. Ciprofloxacin was the most frequently studied drug. Outcomes of the studies were heterogeneous and generally had a high risk of bias. Three small studies, two on ciprofloxacin and one on clarithromycin, compared the pharmacokinetics of febrile patients with those of clinically recovered patients and suggested that bioavailability was not altered in these patients. Other studies either compared the pharmacokinetics in febrile patients with reported pharmacokinetic values from earlier studies in healthy volunteers (n = 2), or provided no comparison at all and were non-conclusive (n = 4).

Conclusion

There is a clear knowledge gap regarding the bioavailability of orally administered antibiotics in non-ICU patients during the initial phase of a systemic infection. Well-designed studies on this topic are necessary to elucidate whether patients can benefit from the advantages of an earlier IV-to-oral switch.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-021-05919-w.

LC-MS/MS method for nine different antibiotics

BACKGROUND AND AIMS

TDM of antibiotics can bring benefits to patients and healthcare systems by providing better treatment and saving healthcare resources. We aimed to develop a multi-analyte method for several diverse antibiotics using LC-MS/MS.

MATERIALS AND METHODS

Sample preparation consisted of protein precipitation with methanol, dilution and online extraction using a Turboflow Cyclone column. Separation was performed on a Synergi 4 µm Max RP column and deuterated forms of three antibiotics were used as internal standards.

RESULTS

We present a LC-MS/MS method for the quantitative determination of nine antibiotics, including five cephalosporins, the carbapenem ertapenem, the fluoroquinolone ciprofloxacin as well as the combination drug trimethoprim-sulfamethoxazole from plasma. Additionally, unbound ertapenem and cefazolin were analyzed in plasma water after ultrafiltration using plasma calibrators. Results from routine TDM show the applicability of the method.

CONCLUSION

The presented method is precise and accurate and was introduced in a university hospital, permitting fast TDM of all nine analytes. It was also used in a clinical study for measuring cefazolin free and total concentrations.

Antibiotic treatment in patients with sepsis: a narrative review

Sepsis is a medical emergency and life-threatening condition due to a dysregulated host response to infection, with unacceptably high morbidity and mortality. Similar to acute myocardial infarction or cerebral vascular accident, sepsis is a severe and continuous time-dependent condition. Thus, in the case of sepsis, early and adequate administration of antimicrobials must be a priority, ideally within the first hour of diagnosis, simultaneously with organ support.As a consequence of the emergence of multidrug-resistant pathogens, the choice of antimicrobials should be performed according to the local pathogen patterns of resistance. Individual antimicrobial optimization is essential to achieve adequate concentrations of antimicrobials, to reduce adverse effects, and to ensure successful outcomes, as well as preventing the emergence of multidrug-resistant pathogens. The loading dose is the administration of an initial higher dose of antimicrobials, regardless of the presence of organ dysfunction. Further doses should be implemented according to pharmacokinetics/pharmacodynamics of antimicrobials and should be adjusted according to the presence of renal or liver dysfunction. Extended or continuous infusion of beta-lactams and therapeutic drug monitoring can help to achieve therapeutic levels of antimicrobials. Duration and adequacy of treatment must be reviewed at regular intervals to allow effective de-escalation and administration of short courses of antimicrobials for most patients. Antimicrobial stewardship frameworks, leadership, focus on the optimal duration of treatments, de-escalation, and novel diagnostic stewardship approaches will help us to improve patients the process of care and overall quality of care.

Preanalytical Stability of Piperacillin, Tazobactam, Meropenem, and Ceftazidime in Plasma and Whole Blood Using Liquid Chromatography-Tandem Mass Spectrometry

BACKGROUND

Therapeutic drug monitoring (TDM) is increasingly used to optimize the dosing of beta-lactam antibiotics in critically ill patients. However, beta-lactams are inherently unstable and degrade over time. Hence, patient samples need to be appropriately handled and stored before analysis to generate valid results for TDM. The appropriate handling and storage conditions are not established, with few and conflicting studies on the stability of beta-lactam antibiotics in clinical samples. The aim of this study was to assess the preanalytical stability of piperacillin, tazobactam, meropenem, and ceftazidime in human plasma and whole blood using a liquid chromatography-tandem mass spectrometry method for simultaneous quantification.

METHODS

A reverse phase liquid chromatography-tandem mass spectrometry method for the quantification of piperacillin, tazobactam, meropenem, and ceftazidime in plasma after protein precipitation was developed and validated. The preanalytical stability of these beta-lactams was assessed in EDTA- and citrate-anticoagulated plasma at 24, 4, and -20°C. The whole blood stability of the analytes in EDTA-anticoagulated tubes was assessed at 24°C. Stability was determined by nonlinear regression analysis defined by the lower limit of the 95th confidence interval of the time to 15% of degradation.

RESULTS

Based on the lower limit of the 95th confidence interval of the time to 15% of degradation, piperacillin, tazobactam, meropenem, and ceftazidime were stable in EDTA-anticoagulated plasma for at least 6 hours at 24°C, 3 days at 4°C, and 4 days at -20°C. Stability in EDTA- and citrate-anticoagulated plasma was similar. Stability in whole blood was similar to plasma at 24°C.

CONCLUSIONS

Plasma samples for the TDM of piperacillin, tazobactam, meropenem, and ceftazidime should be processed within 6 hours if kept at room temperature and within 3 days if kept at 4°C. All long-term storage of samples should be at -80°C.

Early target attainment of continuous infusion piperacillin/tazobactam and meropenem in critically ill patients: A prospective observational study

PURPOSE

To evaluate target attainment of empirically dosed continuous infusion piperacillin/tazobactam (TZP) and meropenem (MER) in critically ill patients.

PATIENTS AND METHODS

Patients were sampled on a daily basis. TZP or MER concentrations were evaluated during the first two days antibiotic therapy. The lower limit of the target range was defined as unbound concentrations equaling 4 times the epidemiological cutoff value of P. aeruginosa. The upper limit of the target range was based on the risk of toxicity, i.e. unbound concentrations >160 mg/L for TZP and > 45 mg/L for MER. Multivariable logistic regression was used to evaluate factors associated with target attainment.

RESULTS

Data from 253 patients were analyzed. Overall, 76/205 (37.1%) and 36/48 (75%) of the patients receiving TZP or MER respectively, attained target concentrations. In multivariable analysis, estimated creatinine clearance was identified as a risk factor for target non-attainment (OR 0.988, 95%CI [0.982;0.994]). Patients receiving MER were more likely to attain target concentrations compared with patients receiving TZP (OR 6.02, 95%CI [2.12;18.4]).

CONCLUSION

Target attainment of empiric antibiotic therapy in critically ill patients was low (37%) for TZP and moderate (75%) for MER, despite the use of a loading dose and despite optimization of the mode of infusion.

Ceftazidime-Avibactam Susceptibility Breakpoints against Enterobacteriaceae and Pseudomonas aeruginosa

Clinical susceptibility breakpoints against Enterobacteriaceae and Pseudomonas aeruginosa for the ceftazidime-avibactam dosage regimen of 2,000/500 mg every 8 h (q8h) by 2-h intravenous infusion (adjusted for renal function) have been established by the FDA, CLSI, and EUCAST as susceptible (MIC, ≤8 mg/liter) and resistant (MIC, >8 mg/liter). The key supportive data from pharmacokinetic/pharmacodynamic analyses, in vitro surveillance, including molecular understanding of relevant resistance mechanisms, and efficacy in regulatory clinical trials are collated and analyzed here.

Optimisation of antimicrobial dosing based on pharmacokinetic and pharmacodynamic principles

While suboptimal dosing of antimicrobials has been attributed to poorer clinical outcomes, clinical cure and mortality advantages have been demonstrated when target pharmacokinetic (PK) and pharmacodynamic (PD) indices for various classes of antimicrobials were achieved to maximise antibiotic activity. Dosing optimisation requires a good knowledge of PK/PD principles. This review serves to provide a foundation in PK/PD principles for the commonly prescribed antibiotics (β-lactams, vancomycin, fluoroquinolones and aminoglycosides), as well as dosing considerations in special populations (critically ill and obese patients). PK principles determine whether an appropriate dose of antimicrobial reaches the intended pathogen(s). It involves the fundamental processes of absorption, distribution, metabolism and elimination, and is affected by the antimicrobial's physicochemical properties. Antimicrobial pharmacodynamics define the relationship between the drug concentration and its observed effect on the pathogen. The major indicator of the effect of the antibiotics is the minimum inhibitory concentration. The quantitative relationship between a PK and microbiological parameter is known as a PK/PD index, which describes the relationship between dose administered and the rate and extent of bacterial killing. Improvements in clinical outcomes have been observed when antimicrobial agents are dosed optimally to achieve their respective PK/PD targets. With the rising rates of antimicrobial resistance and a limited drug development pipeline, PK/PD concepts can foster more rational and individualised dosing regimens, improving outcomes while simultaneously limiting the toxicity of antimicrobials.

Clinical application of microsampling versus conventional sampling techniques in the quantitative bioanalysis of antibiotics: a systematic review

Conventional sampling techniques for clinical pharmacokinetic studies often require the removal of large blood volumes from patients. This can result in a physiological or emotional burden, particularly for neonates or pediatric patients. Antibiotic pharmacokinetic studies are typically performed on healthy adults or general ward patients. These may not account for alterations to a patient’s pathophysiology and can lead to suboptimal treatment. Microsampling offers an important opportunity for clinical pharmacokinetic studies in vulnerable patient populations, where smaller sample volumes can be collected. This systematic review provides a description of currently available microsampling techniques and an overview of studies reporting the quantitation and validation of antibiotics using microsampling. A comparison of microsampling to conventional sampling in clinical studies is included.

Simultaneous quantification of cefepime, meropenem, ciprofloxacin, moxifloxacin, linezolid and piperacillin in human serum using an isotope-dilution HPLC-MS/MS method

The aim of the current study was to develop and validate a robust multi-analyte high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) method for simultaneous quantification of cefepime, meropenem, ciprofloxacin, moxifloxacin, linezolid and piperacillin, which are the most commonly used antibiotics in intensive care units. Sample clean-up included a protein precipitation protocol, followed by chromatographic separation on a C₈ reverse phase HPLC column within 4 min, using a formic acid-ammonium formiate methanol step-elution gradient. All compounds were detected with electrospray ionization (ESI+) mass spectrometry in multiple reaction time monitoring. The method was validated according to the protocol from the European Medicines Agency and was thoroughly evaluated for interferences and quantification linearity. Linear relationships between peak area responses and drug concentrations were obtained in the range of 0.25-200 mg/l for cefepime, 0.25-120 mg/l for meropenem, 0.05-10 mg/l for ciprofloxacin, 0.125-10 mg/l for moxifloxacin, 0.125-50 mg/l for linezolid and 0.5-400 mg/l for piperacillin with an R² > 0.997. Imprecision and inaccuracy values (both intra- and inter-assay) were ≤ 6.8% and ≤10.9% for all analytes in quality control samples, respectively. The assay proved to be selective for the study antibiotics, and the internal standards consistently compensated for matrix effects. The described simple and reliable HPLC-MS/MS assay is a powerful tool for routine TDM of cefepime, meropenem, ciprofloxacin, moxifloxacin, linezolid and piperacillin in human serum in clinical laboratories. With a total process time of approximately 30 min, it allows for accurate and selective quantification up to the expected pharmacokinetic peak concentrations.

Feasibility and applicability of antimicrobial stewardship in immunocompromised patients

PURPOSE OF REVIEW

Antimicrobial stewardship is the primary intervention in the battle against antimicrobial resistance, but clinicians do not always apply many key antimicrobial stewardship principles to patients with significant immune defects due to lack of data and fear of bad outcomes. We review evidence regarding the application of stewardship principles to immunocompromised patients, with a focus on solid organ and hematopoietic stem cell transplant recipients.

RECENT FINDINGS

Antimicrobial stewardship programs (ASPs), targeting immunocompromised patient populations such as oncology and transplant, are gaining traction. Emerging literature suggests that several stewardship interventions can be adapted to immunocompromised hosts and improve antimicrobial utilization, but data supporting improved outcomes is very limited.

SUMMARY

The application of antimicrobial stewardship principles to immunocompromised patients is feasible, necessary, and urgent. As antimicrobial stewardship programs gain momentum across a diverse range of healthcare settings more immunocompromised patients will fall under their purview. It is imperative that centers applying antimicrobial stewardship principles share their experience and establish collaborative research efforts to advance our knowledge base in applying antimicrobial stewardship initiatives to immunocompromised host populations, both in terms of programmatic success and patient outcomes.

A simple ultra-high-performance liquid chromatography-high resolution mass spectrometry assay for the simultaneous quantification of 15 antibiotics in plasma

Antibiotic (ATB) treatment of critically ill patients with pathophysiological injuries remains a challenge due to the constant increase in antimicrobial resistance. Therapeutic drug monitoring (TDM) is advised for ATB dose adjustments to avoid suboptimal concentrations and dose-related adverse effects. Therefore, a single and reliable analytical method for a broad selection of ATBs was developed using a high-resolution mass spectrometry (HRMS) platform for frequent use in intensive care units. An UHPLC assay coupled to high resolution accurate mass acquisition has been developed for the quantification of penicillins (amoxicillin, oxacillin, piperacillin, and ticarcillin), cephalosporines (cefepime, cefotaxime, ceftazidime, and ceftriaxone), carbapenems (ertapenem, imipenem, and meropenem), lincosamide (clindamycin), quinolones (ofloxacin and ciprofloxacin) and tazobactam. Plasma samples (100μL) were spiked with an internal standard solution followed by protein precipitation. Separation was achieved on an Accucore C18 column, which enabled sample analysis every 9min. All compounds were detected in electrospray positive ion mode and quantified with a linear regression between 0.5 and 32mg/L (r2>0.998). Overall precision and accuracy did not exceed 15%. No significant matrix effect was observed for the studied ATBs. Stored stock solutions at -20°C were stable for 6 months, except for amoxicillin and imipenem. Analytes in plasma were stable for 24h under ambient conditions as well as in post-preparation in an autosampler, except for amoxicillin and imipenem. This HRMS assay provides the simultaneous quantification of 15 ATB; it fulfills the usual quality criteria and was successfully applied for routine TDM of ATBs. The method is based on a full scan acquisition, and it would be easy to add other compounds to the present panel in the future, as this assay has already been proven to be efficient for different classes of compounds.

Analysis of an Infectious Diseases Pharmacist on Call Pager Program to Inform Educational Efforts

Background: An on call infectious diseases (ID) pharmacist may be used as a resource for physicians, pharmacists, and other health care providers to help answer questions regarding anti-infective agents. Objective: To assess type, requestor, resources dedicated, and temporal trends of questions received through an ID pharmacist on call pager program. A secondary objective was to gather insight as to how this information was utilized to inform educational initiatives. Methods: This was a retrospective study of questions received by the ID pharmacist on call via pager at a large academic medical center. Question data were documented in a central database and analyzed to assess temporal trends and question type, and qualitatively analyzed to determine areas for targeted educational efforts. Results: The ID pharmacist on call recorded 545 questions during the 1-year study period; questions were composed of various antimicrobial agent-related queries, including antibiotic spectrum and selection (n = 251, 46.1%), dosing of antimicrobials (n = 195, 35.8%), and drug monitoring (n = 26, 4.8%). Targeted educational initiatives secondary to questions received included pharmacist education regarding the use of polymyxin antibiotics and antibiotic dosing protocol updates. Conclusions: An ID pharmacist on call pager program was utilized to inquire about antibiotic spectrum and selection for the majority of questions. Records of questions received may be utilized to direct educational efforts and create or revise targeted resources for pharmacists and other clinicians.