Rapid quantification of six β-lactams to optimize dosage regimens in severely septic patients

Halloysite nanotubes-based hybrid silica monolithic spin tip for hydrophilic solid-phase extraction of sulbactam, cefoperazone, and cefuroxime in whole blood

In this study, we proposed a novel method utilizing polyethyleneimine (PEI)-modified halloysite nanotubes (HNTs)-based hybrid silica monolithic spin tip to analyze hydrophilic β-lactam antibiotics and β-lactamases inhibitors in whole blood samples for the first time. HNTs were incorporated directly into the hybrid silica monolith via a sol-gel method, which improved the hydrophilicity of the matrix. The as-prepared monolith was further modified with PEI by glutaraldehyde coupling reaction. It was found that the PEI-modified HNTs-based hybrid silica monolith enabled a large adsorption capacity of cefoperazone at 35.7 mg g-1. The monolithic spin tip-based purification method greatly reduced the matrix effect of whole blood samples and had a detection limit as low as 0.1 - 0.2 ng mL-1. In addition, the spiked recoveries of sulbactam, cefuroxime, and cefoperazone in blank whole blood were in the range of 89.3-105.4 % for intra-day and 90.6-103.5 % for inter-day, with low relative standard deviations of 1.3-7.2 % and 4.9-10.5 %, respectively. This study introduces a new strategy for preparing nanoparticles incorporated in a hybrid silica monolith with a high adsorption capacity. Moreover, it offers a valuable tool to monitor sulbactam, cefoperazone, and cefuroxime in whole blood from pregnant women with the final aim of guiding their administration.

Developing a Method for Quantifying Meropenem in Children-Volumetric Adsorptive Microsampling Versus Plasma Sampling

BACKGROUND

Meropenem is a carbapenem antibiotic often used in pediatric intensive care units due to its broad spectrum of activity. Therapeutic drug monitoring (TDM) is a useful tool to increase the effectiveness of meropenem by adjusting the dose based on plasma levels; however, the relatively large sample volume required for TDM can limit its use in children. Therefore, this study aimed to determine meropenem concentrations and consequently perform TDM effectively using the smallest possible sample volume. Volumetric absorptive microsampling (VAMS) is a sampling technology developed to collect a small, precise volume of blood. For the applicability of VAMS in TDM, plasma concentrations must be reliably calculated from whole blood (WB) collected by VAMS.

METHODS

VAMS technology using 10 µL of WB was evaluated and compared with EDTA-plasma sampling. High-performance liquid chromatography with UV detection was applied to quantify meropenem in VAMS and plasma samples after the removal of proteins by precipitation. Ertapenem was used as the internal standard. Samples were collected simultaneously from critically ill children receiving meropenem using VAMS and traditional sampling.

RESULTS

It was found that no consistent factor could be determined to calculate meropenem plasma concentrations from the WB, indicating that VAMS was not reliable in the TDM of meropenem. Therefore, to reduce the required sample amount in pediatric patients, a method for quantifying meropenem from 50 µL of plasma with a lower limit of quantification of 1 mg/L was developed and successfully validated.

CONCLUSIONS

A simple, reliable, and low-cost method was established using high-performance liquid chromatography-UV to determine the concentration of meropenem in 50 µL of plasma. VAMS using WB does not seem to be suitable for TDM of meropenem.

Therapeutic drug monitoring of carbapenem antibiotics in critically ill patients: an overview of principles, recommended dosing regimens, and clinical outcomes

INTRODUCTION

The importance of antibiotic treatment for sepsis in critically ill septic patients is well established. Consistently achieving the dose of antibiotics required to optimally kill bacteria, minimize the development of resistance, and avoid toxicity is challenging. The increasing understanding of the pharmacokinetic and pharmacodynamic (PK/PD) characteristics of antibiotics, and the effects of critical illness on key PK/PD parameters, is gradually re-shaping how antibiotics are dosed in critically ill patients.

AREAS COVERED

The PK/PD characteristics of commonly used carbapenem antibiotics, the principles of the application of therapeutic drug monitoring (TDM), and current as well as future methods of utilizing TDM to optimally devise dosing regimens will be reviewed. The limitations and evidence-base supporting the use of carbapenem TDM to improve outcomes in critically ill patients will be examined.

EXPERT OPINION

It is important to understand the principles of TDM in order to correctly inform dosing regimens. Although the concept of TDM is attractive, and the ability to utilize PK software to optimize dosing in the near future is expected to rapidly increase clinicians' ability to meet pre-defined PK/PD targets more accurately, current evidence provides only limited support for the use of TDM to guide carbapenem dosing in critically ill patients.

Fast and Sensitive Method for Simultaneous Quantification of Meropenem and Vaborbactam in Human Plasma Microsamples by Liquid Chromatography-Tandem Mass Spectrometry for Therapeutic Drug Monitoring

Meropenem (MRP)-Vaborbactam (VBR) is a novel beta-lactam/beta-lactamase inhibitor used for the management of difficult-to-treat Gram-negative infections. Among critically ill patients, MRP-VBR shows remarkable inter-individual variability in pharmacokinetic behavior, thus justifying the implementation of therapeutic drug monitoring (TDM) for improving real-time management in different challenging scenarios. In this study, we developed and validated a fast and sensitive Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) method for the simultaneous quantification of MRP and VBR in human plasma microsamples of 3 microliters. The analysis required only a single-step sample preparation and was performed by means of a fast chromatographic run of 4 min, followed by positive electrospray ionization and detection on a high-sensitivity triple quadrupole tandem mass spectrometer operated in multiple reaction monitoring modes. The straightforward analytical procedure was successfully validated, based on the EMA guidelines, in terms of specificity, sensitivity, linearity, precision, accuracy, matrix effect, extraction recovery, the limit of quantification, and stability. The novel method was successfully applied for simultaneously measuring MRP and VBR concentrations in more than 42 plasma samples collected from critically ill patients affected by carbapenem-resistant Gram-negative bacteria infections.

Simple HPLC-UV Method for Piperacillin/Tazobactam Assay in Human Plasma

BACKGROUND

Piperacillin (Pip)/tazobactam (Taz) is a broad-spectrum antimicrobial agent that has been commonly used in the intensive care unit for severe and life-threatening infections. Recent evidence suggests that therapeutic drug monitoring (TDM) for Pip could be beneficial in clinical practice to facilitate dose optimization and increase the odds of treatment success. The aim was to develop and validate a sensitive and simple high-performance liquid chromatography (HPLC) method for the simultaneous quantification of Pip and Taz in human plasma.

METHODS

Samples (0.3 mL) were deproteinized with acetonitrile. The supernatant was evaporated and then reconstituted and injected into the HPLC. The chromatographic analysis was carried out by using the C18 column and gradient elution with the acetonitrile:water mobile phase mixture with 0.1% trifluoracetic acid at a flow rate of 0.8 mL/min using a UV detector at 218 nm.

RESULTS

The method had acceptable linearity (r² > 0.99) over the concentration ranges of 0.5-400 μg/mL and 1-100 μg/mL for Pip and Taz, respectively. The method demonstrated acceptable inter- and intra-day precision and accuracy within ±20% with adequate stability results.

CONCLUSION

The developed method is sensitive and simple and utilizes simple sample preparation and elution steps, making it suitable and practical for Pip/Taz TDM.

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.

Methods for Determination of Meropenem Concentration in Biological Samples

Measuring the concentration of antibiotics in biological samples allow implementation of therapeutic monitoring of these drugs and contribute to the adjustment of the dosing regimen in patients. This increases the effectiveness of antimicrobial therapy, reduces the toxicity of these drugs and prevents the development of bacterial resistance. This review article summarizes current knowledge on methods for determining concentration of meropenem, an antibiotic drug from the group of carbapenems, in different biological samples. It provides a brief discussion of the chemical structure, physicochemical and pharmacokinetic properties of meropenem, different sample preparation techniques, use of apparatus and equipment, knowledge of the advantages and limitations of available methods, as well as directions in which new methods should be developed. This review should facilitate clinical laboratories to select and apply one of the established methods for measuring of meropenem, as well as to provide them with the necessary knowledge to develop new methods for quantification of meropenem in biological samples according to their needs.

Quantitative Determination of Unbound Piperacillin and Imipenem in Biological Material from Critically Ill Using Thin-Film Microextraction-Liquid Chromatography-Mass Spectrometry

β-Lactam antibiotics are most commonly used in the critically ill, but their effective dosing is challenging and may result in sub-therapeutic concentrations that can lead to therapy failure and even promote antimicrobial resistance. In this study, we present the analytical tool enabling specific and sensitive determination of the sole biologically active fraction of piperacillin and imipenem in biological material from the critically ill. Thin-film microextraction sampling technique, followed by rapid liquid chromatography–tandem mass spectrometry (LC-MS/MS) analysis, was optimized and validated for the quantitative determination of antibiotics in blood and bronchoalveolar lavage (BAL) specimens collected from intensive care unit (ICU) patients suffering from ventilation-associated pneumonia (n = 18 and n = 9, respectively). The method was optimized and proved to meet the criteria of US Food and Drug Administration (FDA) guidelines for bioanalytical method validation. Highly selective, sensitive, accurate and precise analysis by means of thin-film microextraction–LC-MS/MS, which is not affected by matrix-related factors, was successfully applied in clinical settings, revealing poor penetration of piperacillin and imipenem from blood into BAL fluid (reflecting the site of bacterial infection), nonlinearity in antibiotic binding to plasma-proteins and drug-specific dependence on creatinine clearance. This work demonstrates that only a small fraction of biologically active antibiotics reach the site of infection, providing clinicians with a high-throughput analytical tool for future studies on personalized therapeutic drug monitoring when tailoring the dosing strategy to an individual patient.

Rapid Detection of Multiple Classes of β-Lactam Antibiotics in Blood Using an NDM-1 Biosensing Assay

Currently, assays for rapid therapeutic drug monitoring (TDM) of β-lactam antibiotics in blood, which might be of benefit in optimizing doses for treatment of critically ill patients, remain challenging. Previously, we developed an assay for determining the penicillin-class antibiotics in blood using a thermometric penicillinase biosensor. The assay eliminates sample pretreatment, which makes it possible to perform semicontinuous penicillin determinations in blood. However, penicillinase has a narrow substrate specificity, which makes it unsuitable for detecting other classes of β-lactam antibiotics, such as cephalosporins and carbapenems. In order to assay these classes of clinically useful antibiotics, a novel biosensor was developed using New Delhi metallo-β-lactamase-1 (NDM-1) as the biological recognition layer. NDM-1 has a broad specificity range and is capable of hydrolyzing all classes of β-lactam antibiotics in high efficacy with the exception of monobactams. In this study, we demonstrated that the NDM-1 biosensor was able to quantify multiple classes of β-lactam antibiotics in blood plasma at concentrations ranging from 6.25 mg/L or 12.5 mg/L to 200 mg/L, which covered the therapeutic concentration windows of the tested antibiotics used to treat critically ill patients. The detection of ceftazidime and meropenem was not affected by the presence of the β-lactamase inhibitors avibactam and vaborbactam, respectively. Furthermore, both free and protein-bound β-lactams present in the antibiotic-spiked plasma samples were detected by the NDM-1 biosensor. These results indicated that the NDM-1 biosensor is a promising technique for rapid TDM of total β-lactam antibiotics present in the blood of critically ill patients.

Population Pharmacokinetics of Vancomycin and Meropenem in Pediatric Extracorporeal Membrane Oxygenation Support

Objective: Describe primary pharmacokinetic/pharmacodynamic (PK/PD) parameters of vancomycin and meropenem in pediatric patients undergoing ECMO and analyze utilized dosing to reach PK/PD target.

Design: Prospective, multicentric, population PK analysis.

Setting: Two hospitals with pediatric intensive care unit.

Patients: Pediatric patients (1 month - 15 years old) receiving vancomycin and meropenem for empiric or definitive infection treatment while ECMO support.

Measurements and Main Results: Four serum concentration were obtained for patients receiving vancomycin (n = 9) and three for meropenem (n = 9). The PK/PD target for vancomycin was a ratio of the area under the curve to the minimal inhibitory concentration (AUC/MIC) of >400, and for meropenem was 4 times above MIC for 50% of the dosing interval (fT_50% > 4xMIC). Pharmacokinetic modeling was performed using PMetrics 1.5.0. We included nine patients, with 11 PK profiles for each antimicrobial. The median age of patients was 4 years old (2 months - 13 years) and 45% were male. Creatinine clearance (CL) was 183 (30–550) ml/min/1.73 m². The median dose was 13.6 (range 10–15) mg/kg every 6–12 h and 40 mg/kg every 8–12 h for vancomycin and meropenem, respectively. Two compartment models were fitted. Weight was included as a covariate on volume of the central compartment (Vc) for meropenem. Weight was included as a covariate on both Vc and clearance (CL) and serum creatinine was also included as a covariate on CL for vancomycin. The pharmacokinetic parameters CL and Vc were 0.139 ± 0.102 L/h/kg and 0.289 ± 0.295 L/kg for meropenem and 0.060 ± 0.055 L/h/kg and 0.419 ± 0.280 L/kg for vancomycin, respectively. Across each dosing interval 91% of patients achieved the PK/PD targets for adequate exposure for meropenem and 63.6% for vancomycin.

Conclusion: Pharmacokinetic/pharmacodynamic objectives for vancomycin were achieved partially with conventional doses and higher dosing with extended infusion were needed in the case of meropenem.

A fast, cost-saving and sensitive method for determination of cefuroxime in plasma by HPLC with ultraviolet detection

Cefuroxime (CFX) is a broad-spectrum second-generation cephalosporin and one of the best choices for antibiotic prophylaxis. However, when used in critically ill patients, it may present changes in its pharmacokinetic properties. Therefore, therapeutic drug monitoring of CFX is necessary for effective dosing strategies. A simple, rapid and sensitive liquid chromatographic method with UV detection was developed and validated for the quantification of CFX in plasma. The method involved a single-step precipitation of proteins with methanol and trifluoroacetic acid. Cefuroxime was analyzed on a Brisa LC² C₁₈ column in isocratic mode consisting of 0.1% trifluoroacetic acid in water and acetonitrile (75:25) with UV detection at a wavelength of 280 nm. The retention times of CFX and cephazolin (internal standard) were 9.8 and 7.4 min, respectively. The calibration curve was linear over a concentration range of 0.25-50 μg/ml. The limits of detection and quantification were 0.1 μg/ml and 0.25 μg/ml, respectively. The accuracy and precision were always <10%. The mean recovery was 93.52%. This fast and simple method could be applied in routine analysis and pharmacokinetic studies.

β-Lactam pharmacodynamics in Gram-negative bloodstream infections in the critically ill

OBJECTIVES

To determine the β-lactam exposure associated with positive clinical outcomes for Gram-negative blood stream infection (BSI) in critically ill patients.

PATIENTS AND METHODS

Pooled data of critically ill patients with mono-microbial Gram-negative BSI treated with β-lactams were collected from two databases. Free minimum concentrations (fCmin) of aztreonam, cefepime, ceftazidime, ceftriaxone, piperacillin (co-administered with tazobactam) and meropenem were interpreted in relation to the measured MIC for targeted bacteria (fCmin/MIC). A positive clinical outcome was defined as completion of the treatment course or de-escalation, without other change of antibiotic therapy, and with no additional antibiotics commenced within 48 h of cessation. Drug exposure breakpoints associated with positive clinical outcome were determined by classification and regression tree (CART) analysis.

RESULTS

Data from 98 patients were included. Meropenem (46.9%) and piperacillin/tazobactam (36.7%) were the most commonly prescribed antibiotics. The most common pathogens were Escherichia coli (28.6%), Pseudomonas aeruginosa (19.4%) and Klebsiella pneumoniae (13.3%). In all patients, 87.8% and 71.4% achieved fCmin/MIC ≥1 and fCmin/MIC >5, respectively. Seventy-eight patients (79.6%) achieved positive clinical outcome. Two drug exposure breakpoints were identified: fCmin/MIC >1.3 for all β-lactams (predicted difference in positive outcome 84.5% versus 15.5%, P < 0.05) and fCmin/MIC >4.95 for meropenem, aztreonam or ceftriaxone (predicted difference in positive outcome 97.7% versus 2.3%, P < 0.05).

CONCLUSIONS

A β-lactam fCmin/MIC >1.3 was a significant predictor of a positive clinical outcome in critically ill patients with Gram-negative BSI and could be considered an antibiotic dosing target.

Microsampling Assays for Pharmacokinetic Analysis and Therapeutic Drug Monitoring of Antimicrobial Drugs in Children: A Critical Review

BACKGROUND

With the increasing prevalence of multidrug resistant organisms, therapeutic drug monitoring (TDM) has become a common tool for assuring the safety and efficacy of antimicrobial drugs at higher doses. Microsampling techniques, including dried blood spotting (DBS) and volumetric absorptive microsampling (VAMS), are attractive tools for TDM and pediatric clinical research. For microsampling techniques to be a useful tool for TDM, it is necessary to establish the blood-plasma correlation and the therapeutic window of antimicrobial drugs in the blood.

METHODS

DBS involves the collection of small volumes of blood (30-50 µL per spot) on a filter paper, whereas VAMS allows the accurate and precise collection of a fixed volume of blood (10-30 µL) with microsampling devices. One of the major advantages of VAMS is that it reduces or eliminates the volumetric blood hematocrit (HCT) bias associated with DBS. Liquid chromatography with tandem mass spectrometry is a powerful tool for the accurate quantification of antimicrobial drugs from small volumes of blood specimens.

RESULTS

This review summarizes the recent liquid chromatography with tandem mass spectrometry assays that have used DBS and VAMS approaches for quantifying antimicrobial drugs. Sample collection, extraction, validation outcomes, including the interassay and intra-assay accuracy and precision, recovery, stability, and matrix effect, as well as the clinical application of these assays and their potential as tools of TDM are discussed herein.

CONCLUSIONS

Microsampling techniques, such as VAMS, provide an alternative approach to traditional plasma sample collection for TDM.

A sensitive and high-throughput quantitative liquid chromatography high-resolution mass spectrometry method for therapeutic drug monitoring of 10 β-lactam antibiotics, linezolid and two β-lactamase inhibitors in human plasma

An ultra-high pressure liquid chromatography high-resolution mass spectrometric (UHPLC-HRMS) method was developed for the simultaneous and sensitive quantification of 10 β-lactam antibiotics (cefepime, meropenem, amoxicillin, cefazolin, benzylpenicillin, ceftazidime, piperacillin, flucloxacillin, cefuroxime and aztreonam), linezolid and β-lactamase inhibitors tazobactam and clavulanic acid in human plasma. Validation according to the EMA guidelines showed excellent within- and between-run accuracy and precision (i.e. between 1.1 and 8.5%) and high sensitivity (i.e. lower limit of quantification between 0.25 and 1 mg/L). The UHPLC-HRMS method enables a short turnaround time and high sensitivity and needs only a small amount of plasma, allowing appropriate routine therapeutic drug monitoring. The short turnaround time is obtained by speeding up the protocol on multiple levels, i.e. fast and workload-efficient sample preparation (i.e. protein precipitation and dilution), short (4 min) instrument run time, simultaneous measurement of all relevant β-lactam antibiotics used in the intensive care unit and the use of the same instrument, column and mobile phases as for the other routine methods in our laboratory.

Personalized antibiotic therapy – a rapid high performance liquid chromatography–tandem mass spectrometry method for the quantitation of eight antibiotics and voriconazole for patients in the intensive care unit

Objectives

For a long time, the therapeutic drug monitoring of anti-infectives (ATDM) was recommended only to avoid the toxic side effects of overdosing. During the last decade, however, this attitude has undergone a significant change. Insufficient antibiotic therapy may promote the occurrence of drug resistance; therefore, the “one-dose-fits-all” principle can no longer be classified as up to date. Patients in intensive care units (ICU), in particular, can benefit from individualized antibiotic therapies.

Methods

Presented here is a rapid and sufficient LC-MS/MS based assay for the analysis of eight antibiotics (ampicillin, cefepime, cefotaxime, ceftazidime, cefuroxime, linezolid, meropenem, and piperacillin) applicated by continuous infusion and voriconazole. In addition a dose adjustment procedure for individualized antibiotic therapy has been established.

Results

The suggested dose adjustments following the initial dosing of 121 patient samples from ICUs, were evaluated over a period of three months. Only a minor percentage of the serum levels were found to be within the target range while overdosing was often observed for β-lactam antibiotics, and linezolid tended to be often underused. The results demonstrate an appreciable potential for β-lactam savings while enabling optimal therapy.

Conclusions

The presented monitoring method provides high specificity and is very robust against various interferences. A fast and straightforward method, the developed routine ensures rapid turnaround time. Its application has been well received by participating ICUs and has led to an expanding number of hospital wards participating in ATDM.

Simultaneous determination of 8 beta-lactams and linezolid by an ultra-performance liquid chromatography method with UV detection and cross-validation with a commercial immunoassay for the quantification of linezolid

Linezolid and beta-lactams are anti-infective drugs frequently used in intensive care unit patients. Critical illness could induce alterations of pharmacokinetic parameters due to changes in the distribution, the metabolism and the elimination process. Therapeutic drug monitoring (TDM) is therefore recommended to prevent mainly under-dosing of beta-lactams or hematological and neurological toxicities of linezolid. In Multi-or Extensively-Drugs Resistant-Tuberculosis Bacteria, the regimen could include linezolid with meropenem and amoxicillin/clavulanate justifying the development of a method allowing their simultaneous quantification. The aim of this work was to develop an in-house ultra-performance liquid chromatography method with UV detection (UHPLC-PDA) allowing the simultaneous determination of 8 beta-lactams (amoxicillin, aztreonam, cefepime, ceftazidime, ceftriaxone, cefuroxime, meropenem and piperacillin) and linezolid and to cross-validate the linezolid quantification with a new commercial immunoassay (ARK kit) tested on a Cobas analyzer. The main advantages of the immunoassay are a 24/24 h random access assay which is fully automated and results provided within 2 h. The interference due to potential co-administrated drugs was evaluated on both methods. The preanalytical factors (type of matrix, stability) for linezolid were also investigated. The influence of hemolysis, icteria or lipemia on the spectroscopic detection of the immunoassay was assessed. The analytical performances were evaluated using the accuracy profiles approach with acceptance limits fixed at ±30%. Seventy patient samples were measured using both methods. No cross-reaction with the tested anti-infective drugs as well as no influence of hemolysis, lipemia, icteria were observed. The linezolid concentration could be measured on heparinized plasma or serum without a significant difference and remained stable for at least 72h at 4°C.The UHPLC-PDA method performed well in the analytical range investigated (0.25-50 mg/L for meropenem, 0.75-50 mg/L for linezolid and 1-200 mg/L for other beta-lactams) with an intermediate precision and a relative bias below 7.6 and 7.7%, respectively. The analytical range of the immunoassay was narrower, from 0.85 to 18.5 mg/L. The precision and relative bias were lower than 8.1% and 4.2%, respectively. Results obtained on clinical samples showed an acceptable difference between methods with a mean bias of -1.8% [95% confidence interval: -5.2% - 1.6%]. To conclude, both methods showed acceptable performance to perform TDM of linezolid considering the therapeutic through target of 2-8 mg/L. The choice of the method should be made according to the degree of emergency of the response required and the field of application justifying or not the simultaneous quantification of beta-lactams and linezolid.

A new HPLC-DAD method for contemporary quantification of 10 antibiotics for therapeutic drug monitoring of critically ill pediatric patients

The common practice of therapeutic drug monitoring (TDM) involves the quantification of drug plasma concentrations at a specific time in a dosing window. Although TDM for antibiotics is not considered mandatory, it may represent a valid tool for clinicians in order to limit antibiotic resistance and avoid therapeutic failures. The aim of our study was to develop and validate a high-performance liquid chromatography-diode array detection method for simultaneous quantification of 10 antibiotics in plasma. This method has a fast analytical procedure that uses the same chromatographic conditions to quantify ceftazidime, ceftriaxone, meropenem, ertapenem, ciprofloxacin, tigecycline, ampicillin, levofloxacin and piperacillin, plus the β-lactamase inhibitor tazobactam. Method validation was ensured by testing selectivity, accuracy, precision, limits of detection and quantification, recovery and stability. The calibration ranges, established accordingly to the expected plasma concentration in patients, showed a coefficient of determination >0.996 for all compounds. Within- and between-days precisions reported a coefficient of variation >15%. Similarly, the accuracy evaluation reported a relative standard deviation of <10% for each antibiotic. The recovery ranged between 97 and 103% for all compounds. This method could represent a useful tool for TDM of antibiotics.

Benefits of prolonged infusion of beta-lactam antibiotics in patients with sepsis: personal perspectives

INTRODUCTION

In the current era of relatively scarce antibiotic production and significant levels of antimicrobial resistance, optimization of pharmacokinetics and pharmacodynamics of antibiotic therapy is mandatory. Prolonged infusion of beta-lactam antibiotics in comparison to the intermittent infusion has the theoretical advantage of better patient outcomes. Apparently, conflicting data in the literature possibly underestimate the benefits of prolonged infusion of antibiotic treatment.

AREAS COVERED

We provide our perspective on the subject based on our experience and by critically evaluating literature data.

EXPERT OPINION COMMENTARY

In our opinion, the available data are suggestive of the beneficial role of prolonged infusion of beta-lactams in regard to piperacillin/tazobactam and carbapenems after administering a loading dose. While more data from randomized controlled trials are necessary to solidify or negate the evident benefits of prolonged infusion of the aforementioned antibiotics, clinicians should strongly consider this mode of administration of relevant antibiotics, especially in patients with severe infections.

Validation of a simple and economic HPLC-UV method for the simultaneous determination of vancomycin, meropenem, piperacillin and tazobactam in plasma samples

Critically ill patients are often affected by several pathophysiological conditions requiring antibiotic administration and, frequently, extracorporeal therapy that significantly alter the normal pharmacokinetics of drugs. Therapeutic drug monitoring (TDM) may assist to establish the correct antibiotic dosage, but a TDM service is usually available only for some aminoglycosides and glycopeptides. The aim of this study is the validation of an HPLC-UV method for the simultaneous quantification of meropenem, vancomycin, piperacillin and tazobactam in human plasma samples. The analytes were extracted from 250 μL of human plasma by the addition of acetonitrile for protein precipitation. After evaporation to dryness of the solvent, samples were reconstituted with 250 μL of mobile phase, and 100 μL were injected in HPLC. Chromatographic analysis was performed using a Kinetex C18 column and an UV/Vis detector set at 220 and 298 nm. The mobile phase was a mixture of phosphate buffer 0.1 M pH 3.15 and methanol in gradient, delivered at 1 mL/min. The method was validated over clinical concentration ranges. For all the analytes, the lower limit of quantification was 1 μg/mL, and the calibration curves were linear between 1 and 100 μg/mL, with coefficients of determination ≥ 0.999. Intra-day precision was < 4%, while inter-day precision was < 7% for each analyte. The applicability of the method has been evaluated by analysing plasma samples collected from 4 critically ill patients undergoing continuous renal replacement therapy. Moreover, the analysis of vancomycin with VANC Flex® confirmed a good correlation between the results of HPLC-UV and commercially available kits usually used by TDM service. The method we developed only requires a small volume of plasma and uses the same sample preparation protocol, stationary phase and elution conditions for all analytes. This method offers the additional advantages of simple and rather inexpensive sample preparation and instrumentation, features that make this method an easy implementation for a general TDM laboratory.

Investigation of early antibiotic use in pediatric patients with acute respiratory infections by high-performance liquid chromatography

In this study, we developed and validated two reliable high-performance liquid chromatography (HPLC) methods for the qualitative detection of six oral β-lactams, which are commonly used in pediatric patients with acute respiratory infections (ARIs). Two distinct reverse-phase chromatographic separations of six β-lactams were obtained. Four β-lactams (cefadroxil, cephalexin, cefaclor and cefixime) in urine were separated using a gradient program with a mobile phase consisting of K₂ HPO₄ buffer (20 mm, pH 2.8) and acetonitrile on a LichroCART 250 × 4.6 mm, Purospher STAR C₁₈ end-capped (5 μm) column. Two remained β-lactams (amoxicillin and cefuroxime) were analyzed using a gradient elution with the mobile phase containing K₂ HPO₄ buffer (20 mm, pH 3.0) and acetonitrile on a LichroCart^® Purospher Star C₈ end-capped column (5 μm, 125 × 4.6 mm). Good linearity within the range of 0.3-30 μg/ml for cefadroxil, cephalexin, cefaclor and cefixime, and 0.2-20 μg/ml for amoxicillin and cefuroxime, was attained. The precisions were <14%. The accuracies ranged from 85.87 to 102.8%. The two validated methods were then applied to determine these six antibiotics in 553 urine samples of pediatric patients with ARIs. As a result, 32.2% were positive with one or more of six tested β-lactams. Cefixime was the most commonly detected agent, accounting for 9.8% of enrolled patients.

Simultaneous determination of eight β-lactam antibiotics in human plasma and cerebrospinal fluid by liquid chromatography coupled to tandem mass spectrometry

Therapeutic drug monitoring of β-lactam antibiotics is increasingly used for dose optimization in the individual patient to increase efficacy and reduce the risk of toxicity. The objective of this work is to develop and validate a fast and reliable method using liquid chromatography coupled to tandem mass spectrometric detection to quantify simultaneously amoxicillin, cloxacillin, cefazolin, cefotaxime, ceftazidime, cefepime, meropenem and piperacillin in plasma and cerebrospinal fluid (CSF). Sample clean-up included protein precipitation with acetonitrile followed by evaporation of the supernatant and reconstitution of the residue with mobile phase solvents. Eight deuterated β-lactam antibiotics were used as internal standards. Chromatographic separation was performed on a C18 column (50 mm x 2.1 mm) using a binary gradient elution of water and acetonitrile both containing 0.1% (v/v) formic acid. The total run time was 8 min. The method was then used to perform therapeutic drug monitoring on 2221 patient plasma samples. 32 CSF samples were also analyzed. This method, with its simple sample preparation provides sensitive, accurate and precise quantification of the plasma and cerebrospinal fluid concentration of β-lactam antibiotics and can be used for therapeutic drug monitoring.

β-Lactam Dosage Regimens in Septic Patients with Augmented Renal Clearance

Augmented renal clearance is commonly observed in septic patients and may result in insufficient β-lactam serum concentrations. The aims of this study were to evaluate potential correlations between drug concentrations or total body clearance of β-lactam antibiotics and measured creatinine clearance and to quantify the need for drug dosage adjustments in septic patients with different levels of augmented renal clearance.

Augmented renal clearance is commonly observed in septic patients and may result in insufficient β-lactam serum concentrations. The aims of this study were to evaluate potential correlations between drug concentrations or total body clearance of β-lactam antibiotics and measured creatinine clearance and to quantify the need for drug dosage adjustments in septic patients with different levels of augmented renal clearance. We reviewed 256 antibiotic measurements (512 drug concentrations) from a cohort of 215 critically ill patients who had a measured creatinine clearance of ≥120 ml/min and who received therapeutic drug monitoring of meropenem, cefepime, ceftazidime, or piperacillin from October 2009 until December 2014 at Erasme Hospital. Population pharmacokinetic (PK) analysis of the data was performed using the Pmetrics software package for R. Fifty-five percent of drug concentrations showed insufficient β-lactam serum concentrations to treat infections due to Pseudomonas aeruginosa. There were significant, yet weak, correlations between measured creatinine clearance and trough concentrations of meropenem (r = −0.21, P = 0.01), trough concentrations of piperacillin (r = −0.28, P = 0.0071), concentrations at 50% of the dosage interval (r = −0.41, P < 0.0001), and total body clearance of piperacillin (r = 0.39, P = 0.0002). Measured creatinine clearance adequately explained changes in drug concentrations in population pharmacokinetic models for cefepime, ceftazidime, and meropenem but not for piperacillin. Therefore, specific PK modeling can predict certain β-lactam concentrations based on renal function but not on absolute values of measured creatinine clearance, easily available for clinicians. Currently, routine therapeutic drug monitoring is required to adjust daily regimens in critically ill patients receiving standard dosing regimens.

Delivering precision antimicrobial therapy through closed-loop control systems

Sub-optimal exposure to antimicrobial therapy is associated with poor patient outcomes and the development of antimicrobial resistance. Mechanisms for optimizing the concentration of a drug within the individual patient are under development. However, several barriers remain in realizing true individualization of therapy. These include problems with plasma drug sampling, availability of appropriate assays, and current mechanisms for dose adjustment. Biosensor technology offers a means of providing real-time monitoring of antimicrobials in a minimally invasive fashion. We report the potential for using microneedle biosensor technology as part of closed-loop control systems for the optimization of antimicrobial therapy in individual patients.

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.

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.

Therapeutic drug monitoring of beta-lactam antibiotics - Influence of sample stability on the analysis of piperacillin, meropenem, ceftazidime and flucloxacillin by HPLC-UV

INTRODUCTION

Therapeutic drug monitoring (TDM) is a useful tool to optimize antibiotic therapy. Increasing interest in alternative dosing strategies of beta-lactam antibiotics, e.g. continuous or prolonged infusion, require a feasible analytical method for quantification of these antimicrobial agents. However, pre-analytical issues including sample handling and stability are to be considered to provide valuable analytical results.

METHODS

For the simultaneous determination of piperacillin, meropenem, ceftazidime and flucloxacillin, a high performance liquid chromatography (HPLC) method including protein precipitation was established utilizing ertapenem as internal standard. Long-term stability of stock solutions and plasma samples were monitored. Furthermore, whole blood stability of the analytes in heparinized blood tubes was investigated comparing storage under ambient conditions and 2-8°C.

RESULTS

A calibration range of 5-200μg/ml (piperacillin, ceftazidime, flucloxacillin) and 2-200μg/ml (meropenem) was linear with r²>0.999, precision and inaccuracy were <9% and <11%, respectively. The successfully validated HPLC assay was applied to clinical samples and stability investigations. At -80°C, plasma samples were stable for 9 months (piperacillin, meropenem) or 13 months (ceftazidime, flucloxacillin). Concentrations of the four beta-lactam antibiotics in whole blood tubes were found to remain within specifications for 8h when stored at 2-8°C but not at room temperature.

CONCLUSIONS

The presented method is a rapid and simple option for routine TDM of piperacillin, meropenem, ceftazidime and flucloxacillin. Whereas long-term storage of beta-lactam samples at -80°C is possible for at least 9 months, whole blood tubes are recommended to be kept refrigerated until analysis.

Development and validation of a measurement procedure based on ultra-high performance liquid chromatography-tandem mass spectrometry for simultaneous measurement of β-lactam antibiotic concentration in human plasma

BACKGROUND

The administration of β-lactam antibiotics in continuous infusion could let optimize the pharmacokinetic/pharmacodynamic parameters, especially in the treatment of serious bacterial infections. In this context, and also due to variability in their plasmatic concentrations, therapeutic drug monitoring (TDM) may be useful to optimize dosing and, therefore, be useful for the clinicians.

MATERIAL AND METHODS

We developed and validated a measurement procedure based on ultra-high performance liquid chromatography-tandem mass spectrometry for simultaneous measurement of amoxicillin, ampicillin, cloxacillin, piperacillin, cefepime, ceftazidime, cefuroxime, aztreonam and meropenem concentrations in plasma. The chromatographic separation was achieved using an Acquity®-UPLC® BEH™ (2.1×100mm id, 1.7μm) reverse-phase C₁₈ column, with a water/acetonitrile linear gradient containing 0.1% formic acid at a 0.4mL/min flow rate. β-Lactam antibiotics and their internal standards were detected by electrospray ionization mass spectrometry in multiple reaction monitoring mode.

RESULTS

Chromatography run time was 7.0min and β-lactam antibiotics eluted at retention times ranging between 1.08 and 1.91min. The lower limits of quantification were between 0.50 and 1.00mg/L. Coefficients of variation and relative bias absolute values were <13.3% and 14.7%, respectively. Recovery values ranged from 55.7% to 84.8%. Evaluation of the matrix effect showed ion enhancement for all antibiotics. No interferences or carry-over were observed.

CONCLUSIONS

Our measurement procedure could be applied to daily clinical laboratory practice to measure the concentration of β-lactam antibiotics in plasma, for instance in patients with bone and joint infections and critically ill patients.

Simultaneous determination of chlortetracycline, ampicillin and sarafloxacin in milk using capillary electrophoresis with electrochemiluminescence detection

A fast, inexpensive and sensitive approach for the simultaneous determination of chlortetracycline, ampicilline and sarafloxacin in milk was developed using capillary electrophoresis coupled with an electrochemiluminescence detector. Under the optimal detection conditions, the linear ranges for chlortetracyline, ampicilline and sarafloxacin were 0.030-5.0, 0.050-5.0 and 0.0040-2.0 μg ml^-1, respectively. The correlation coefficients of chlortetracycline, ampicilline and sarafloxacin were determined as 0.9997, 0.9952 and 0.9978, respectively. Detection limits (S/N = 3) of chlortetracycline, ampicilline and sarafloxacin were found as 0.017, 0.018 and 0.0013 μg ml^-1, respectively. This method was successfully applied for the determination of chlortetracycline, ampicilline and sarafloxacin in milk. The recoveries were between 95.3% and 100%. The relative standard deviations of the detection limit and recovery were less than 2.6% and 3.2%, respectively.

Evaluation of total body weight and body mass index cut-offs for increased cefazolin dose for surgical prophylaxis

French and American guidelines recommend increased dosage regimens of cefazolin (CFZ) for surgical prophylaxis in patients with a body mass index (BMI) ≥ 35 kg/m² or with a total body weight (TBW) ≥ 120 kg. The objective of this study was to evaluate the accuracy of these cut-offs in identifying patients who require CFZ dose adjustment. A pharmacokinetic study was conducted in patients of varying TBW and BMI who received 2 g of CFZ intravenously for prophylaxis prior to digestive surgery. Adequacy of therapy, defined as a serum concentration of unbound CFZ (fCFZ) ≥ 4 mg/L, was evaluated 180 min (T₁₈₀) and 240 min (T₂₄₀) after the start of CFZ infusion. Possible factors associated with insufficient fCFZ levels were also assessed. A P-value of <0.05 was considered statistically significant. A total of 63 patients were included in the study, categorised according to BMI (<35 kg/m², 20 patients; and ≥35 kg/m², 43 patients) and TBW (<120 kg, 41 patients; and ≥120 kg, 22 patients). All patients had adequate drug levels at T₁₈₀ but only 40/63 patients (63%) had adequate levels at T₂₄₀. At T₂₄₀, therapy was adequate in 15/20 patients (75%) and 25/43 patients (58%) with BMI <35 kg/m² and ≥35 kg/m², respectively (P = 0.20), and in 28/41 patients (68%) and 12/22 patients (55%) with TBW <120 kg and ≥120 kg, respectively (P = 0.28). No factor associated with insufficient fCFZ was identified. In conclusion, current BMI and TBW cut-offs are poor indicators of which patients could benefit from increased CFZ dosage regimens.

Simultaneous Determination of Eight β-Lactam Antibiotics, Amoxicillin, Cefazolin, Cefepime, Cefotaxime, Ceftazidime, Cloxacillin, Oxacillin, and Piperacillin, in Human Plasma by Using Ultra-High-Performance Liquid Chromatography with Ultraviolet Detection

A simple and rapid ultra-high-performance liquid chromatography (UHPLC) method using UV detection was developed for the simultaneous determination of eight β-lactam antibiotics in human plasma, including four penicillins, amoxicillin (AMX), cloxacillin (CLX), oxacillin (OXA), and piperacillin (PIP), and four cephalosporins, cefazolin (CFZ), cefepime (FEP), cefotaxime (CTX), and ceftazidime (CAZ). One hundred-microliter samples were spiked with thiopental as an internal standard, and proteins were precipitated by acetonitrile containing 0.1% formic acid. Separation was achieved on a pentafluorophenyl (PFP) column with a mobile phase composed of phosphoric acid (10 mM) and acetonitrile in gradient elution mode at a flow rate of 500 μl/min. Detection was performed at 230 nm for AMX, CLX, OXA, and PIP and 260 nm for CFZ, FEP, CTX, and CAZ. The total analysis time did not exceed 13 min. The method was found to be linear at concentrations ranging from 2 to 100 mg/liter for each compound, and all validation parameters fulfilled international requirements. Between- and within-run accuracy errors ranged from -5.2% to 11.4%, and precision was lower than 14.2%. This simple method requires small-volume samples and can easily be implemented in most clinical laboratories to promote the therapeutic drug monitoring of β-lactam antibiotics. The simultaneous determination of several antibiotics considerably reduces the time to results for clinicians, which may improve treatment efficiency, especially in critically ill patients.

Serum β-lactam concentrations in critically ill patients with cirrhosis: a matched case-control study

BACKGROUND & AIMS

The pharmacokinetics of β-lactam antibiotics have not been well defined in critically ill patients with cirrhosis.

METHODS

We reviewed data from critically ill patients with cirrhosis and matched controls in whom routine therapeutic drug monitoring of two broad-spectrum β-lactam antibiotics (piperacillin/tazobactam and meropenem) had been performed. Serum drug concentrations were measured twice by high-performance liquid chromatography. Antibiotic pharmacokinetics were calculated using a one-compartment model. We considered that therapy was adequate when serum drug concentrations were between 4 and 8 times the minimal inhibitory concentration of Pseudomonas aeruginosa during optimal periods of time for each drug (≥ 50% for piperacillin/tazobactam; ≥ 40% for meropenem).

RESULTS

We studied 38 patients with cirrhosis (16 for piperacillin/tazobactam and 22 for meropenem) and 38 matched controls. Drug dosing was similar in the two groups. The pharmacokinetics analysis showed a lower volume of distribution of meropenem (P = 0.05) and a lower antibiotic clearance of piperacillin/tazobactam (P = 0.009) in patients with cirrhosis than in the matched controls. Patients with cirrhosis were more likely than those without cirrhosis to have excessive serum β-lactam concentrations (P = 0.015), in particular for piperacillin/tazobactam.

CONCLUSIONS

Standard β-lactam antibiotics regimens resulted in excessive serum concentrations in two thirds of the patients with cirrhosis. This was particularly true for piperacillin/tazobactam, probably because of reduced drug clearance.

Assays for therapeutic drug monitoring of β-lactam antibiotics: A structured review

In some patient groups, including critically ill patients, the pharmacokinetics of β-lactam antibiotics may be profoundly disturbed due to pathophysiological changes in distribution and elimination. Therapeutic drug monitoring (TDM) is a strategy that may help to optimise dosing. The aim of this review was to identify and analyse the published literature on the methods used for β-lactam quantification in TDM programmes. Sixteen reports described methods for the simultaneous determination of three or more β-lactam antibiotics in plasma/serum. Measurement of these antibiotics, due to low frequency of usage relative to some other tests, is generally limited to in-house chromatographic methods coupled to ultraviolet or mass spectrometric detection. Although many published methods state they are fit for TDM, they are inconvenient because of intensive sample preparation and/or long run times. Ideally, methods used for routine TDM should have a short turnaround time (fast run-time and fast sample preparation), a low limit of quantification and a sufficiently high upper limit of quantification. The published assays included a median of 6 analytes [interquartile range (IQR) 4-10], with meropenem and piperacillin being the most frequently measured β-lactam antibiotics. The median run time was 8 min (IQR 5.9-21.3 min). There is also a growing number of methods measuring free concentrations. An assay that measures antibiotics without any sample preparation would be the next step towards real-time monitoring; no such method is currently available.

β-Lactam pharmacokinetics during extracorporeal membrane oxygenation therapy: A case-control study

Most adult patients receiving extracorporeal membrane oxygenation (ECMO) require antibiotic therapy, however the pharmacokinetics of β-lactams have not been well studied in these conditions. In this study, data from all patients receiving ECMO support and meropenem (MEM) or piperacillin/tazobactam (TZP) were reviewed. Drug concentrations were measured 2h after the start of a 30-min infusion and just before the subsequent dose. Therapeutic drug monitoring (TDM) results in ECMO patients were matched with those in non-ECMO patients for (i) drug regimen, (ii) renal function, (iii) total body weight, (iv) severity of organ dysfunction and (v) age. Drug concentrations were considered adequate if they remained 4-8× the clinical MIC breakpoint for Pseudomonas aeruginosa for 50% (TZP) or 40% (MEM) of the dosing interval. A total of 41 TDM results (27 MEM; 14 TZP) were obtained in 26 ECMO patients, with 41 matched controls. There were no significant differences in serum concentrations or pharmacokinetic parameters between ECMO and non-ECMO patients, including Vd [0.38 (0.27-0.68) vs. 0.46 (0.33-0.79)L/kg; P=0.37], half-life [2.6 (1.8-4.4) vs. 2.9 (1.7-3.7)h; P=0.96] and clearance [132 (66-200) vs. 141 (93-197)mL/min; P=0.52]. The proportion of insufficient (13/41 vs. 12/41), adequate (15/41 vs. 19/41) and excessive (13/41 vs. 10/41) drug concentrations was similar in ECMO and non-ECMO patients. Achievement of target concentrations of these β-lactams was poor in ECMO and non-ECMO patients. The influence of ECMO on MEM and TZP pharmacokinetics does not appear to be significant.

Temocillin (6 g daily) in critically ill patients: continuous infusion versus three times daily administration

OBJECTIVES

The growing incidence of infections caused by Enterobacteriaceae producing ESBLs has led to increased use of carbapenems. Temocillin, which resists most β-lactamases, may be a useful alternative. The aim of this study was to assess the pharmacokinetics and target attainment rates of 6 g of temocillin daily divided into three administrations every 8 h (three times daily) or administered by continuous infusion in critically ill patients.

PATIENTS AND METHODS

This was a prospective, two-centre, randomized, controlled study in patients with intra-abdominal or lower respiratory tract infections caused by Enterobacteriaceae.

RESULTS

Thirty-two patients were included and analysed for clinical efficacy, and pharmacokinetics were measured in 29 of them. Four patients undergoing continuous veno-venous haemofiltration (CVVH) were analysed separately. Mean, median and range of percentages of the dosing interval during which the free drug concentration remained >16 mg/L were 76.4, 98 and 18.7-98.9 in patients treated three times daily and 98.9, 89.7 and 36.4-99.9 in patients with continuous infusion, respectively. Clinical cure rates were 79% and 93% in each of these groups, respectively (not significant). Patients with CVVH received a daily dose of 750 mg given by continuous infusion and had a mean free drug concentration of only 13.8 ± 1.9 mg/L. No adverse event attributable to temocillin was observed.

CONCLUSIONS

Temocillin (6 g daily) given by continuous infusion allows a larger proportion of critically ill patients to have free drug serum concentrations covering infections caused by Enterobacteriaceae with an MIC of 16 mg/L compared with administration three times daily. Clinical efficacy compared with carbapenems in documented severe infections needs to be further studied.

Broad-spectrum β-lactams in obese non-critically ill patients

Objectives:

Obesity may alter the pharmacokinetics of β-lactams. The goal of this study was to evaluate if and why serum concentrations are inadequate when standard β-lactam regimens are administered to obese, non-critically ill patients.

Subjects and methods:

During first year, we consecutively included infected, obese patients (body mass index (BMI) ⩾30 kg m⁻²) who received meropenem (MEM), piperacillin-tazobactam (TZP) or cefepime/ceftazidime (CEF). Patients with severe sepsis or septic shock, or those hospitalized in the intensive care unit were excluded. Serum drug concentrations were measured twice during the elimination phase by high-performance liquid chromatography. We evaluated whether free or total drug concentrations were >1 time (fT>minimal inhibition concentration (MIC)) or >4 times (T>4MIC) the clinical breakpoints for Pseudomonas aeruginosa during optimal periods of time: ⩾40% for MEM, ⩾50% for TZP and ⩾70% for CEF.

Results:

We included 56 patients (median BMI: 36 kg m⁻²): 14 received MEM, 31 TZP and 11 CEF. The percentage of patients who attained target fT>MIC and T>4MIC were 93% and 21% for MEM, 68% and 19% for TZP, and 73% and 18% for CEF, respectively. High creatinine clearance (107 (range: 6–398) ml min⁻¹) was the only risk factor in univariate and multivariate analyses to predict insufficient serum concentrations.

Conclusions:

In obese, non-critically ill patients, standard drug regimens of TZP and CEF resulted in insufficient drug concentrations to treat infections due to less susceptible bacteria. Augmented renal clearance was responsible for these low serum concentrations. New dosage regimens need to be explored in this patient population (EUDRA-CT: 2011-004239-29).

β-lactam antibiotic concentrations during continuous renal replacement therapy

Introduction

The use of standard doses of β-lactam antibiotics during continuous renal replacement therapy (CRRT) may result in inadequate serum concentrations. The aim of this study was to evaluate the adequacy of unadjusted drug regimens (i.e., similar to those used in patients with normal renal function) in patients treated with CRRT and the influence of CRRT intensity on drug clearance.

Methods

We reviewed data from 50 consecutive adult patients admitted to our Department of Intensive Care in whom routine therapeutic drug monitoring (TDM) of broad-spectrum β-lactam antibiotics (ceftazidime or cefepime, CEF; piperacillin/tazobactam; TZP; meropenem, MEM) was performed using unadjusted β-lactam antibiotics regimens (CEF = 2 g q8h; TZP = 4 g q6h; MEM = 1 g q8h). Serum drug concentrations were measured twice during the elimination phase by high-performance liquid chromatography (HPLC-UV). We considered therapy was adequate when serum drug concentrations were between 4 and 8 times the minimal inhibitory concentration (MIC) of Pseudomonas aeruginosa during optimal periods of time for each drug (≥70% for CEF; ≥ 50% for TZP; ≥ 40% for MEM). Therapy was considered as early (ET) or late (LT) phase if TDM was performed within 48 hours of antibiotic initiation or later on, respectively.

Results

We collected 73 serum samples from 50 patients (age 58 ± 13 years; Acute Physiology and Chronic Health Evaluation II (APACHE II) score on admission 21 (17–25)), 35 during ET and 38 during LT. Drug concentrations were above 4 times the MIC in 63 (90%), but above 8 times the MIC in 39 (53%) samples. The proportions of patients with adequate drug concentrations during ET and LT were quite similar. We found a weak but significant correlation between β-lactam antibiotics clearance and CRRT intensity.

Conclusions

In septic patients undergoing CRRT, doses of β-lactam antibiotics similar to those given to patients with normal renal function achieved drug levels above the target threshold in 90% of samples. Nevertheless, 53% of samples were associated with very high drug levels and daily drug regimens may need to be adapted accordingly.

Simple and Robust Analysis of Cefuroxime in Human Plasma by LC-MS/MS: Application to a Bioequivalence Study

A simple, robust LC-MS/MS assay for quantifying cefuroxime in human plasma was developed. Cefuroxime and tazobactam, as internal standard (IS), were extracted from human plasma by methanol to precipitate protein. Separation was achieved on a Zorbax SB-Aq (4.6 × 250 mm, 5  μ m) column under isocratic conditions. The calibration curve was linear in the concentration range of 0.0525-21.0  μ g/mL (r = 0.9998). The accuracy was higher than 90.92%, while the intra- and interday precision were less than 6.26%. The extraction procedure provides recovery ranged from 89.44% to 92.32%, for both analyte and IS. Finally, the method was successfully applied to a bioequivalence study of a single 500 mg dose of cefuroxime axetil in 22 healthy Chinese male subjects under fasting condition. Bioequivalence was determined by calculating 90% Cls for the ratios of C max, AUC0-t , and AUC0-∞ values for the test and reference products, using logarithmic transformed data. The 90% Cls for the ratios of C max (91.4%~104.2%), AUC0-t (97.4%~110.9%), and AUC0-∞ (97.6%~111.1%) values were within the predetermined range. It was concluded that the two formulations (test for capsule, reference for tablet) analyzed were bioequivalent in terms of rate and extent of absorption and the method met the principle of quick and easy clinical analysis.

Can changes in renal function predict variations in β-lactam concentrations in septic patients?

This study investigated whether variations in creatinine clearance (CLCr) are correlated with changes in β-lactam concentrations or pharmacokinetics in septic patients. Data for 56 adult patients admitted to the ICU in whom routine therapeutic drug monitoring (TDM) of broad-spectrum β-lactams (ceftazidime, cefepime, piperacillin or meropenem) was performed were reviewed. Patients were included if they had at least two TDM during their ICU stay for the same antibiotic and were not concomitantly treated with any extracorporeal replacement therapy. Serum drug concentrations were measured by HPLC-UV. Antibiotic pharmacokinetics were calculated using a one-compartment model and the percentage of time spent above four times the MIC (%T>4×MIC) for Pseudomonas aeruginosa and the antibiotic clearance (ATB-CL) were obtained. CLCr was measured on the same day as the TDM using 24-h urine collection. The %T>4×MIC and ATB-CL were significantly correlated with CLCr at the first (r=-0.41, P=0.002; r=0.56, P<0.001, respectively) and second (r=-0.61, P<0.001; r=0.63, P<0.001, respectively) TDM. However, changes in ATB-CL were only weakly correlated with changes in CLCr (r=0.34, P=0.01). The proportion of patients with insufficient β-lactam concentrations at the first and second TDM were 39% and 30%, respectively, and increased proportionally to CLCr. Although CLCr was significantly correlated with concentrations and clearance of broad-spectrum β-lactams, changes in CLCr did not reliably predict variations in drug pharmacokinetics/pharmacodynamics. Routine TDM should be considered to adapt β-lactam doses in this setting.

Case-control study of drug monitoring of β-lactams in obese critically ill patients

Severe sepsis and septic shock can alter the pharmacokinetics of broad-spectrum β-lactams (meropenem, ceftazidime/cefepime, and piperacillin-tazobactam), resulting in inappropriate serum concentrations. Obesity may further modify the pharmacokinetics of these agents. We reviewed our data on critically ill obese patients (body mass index of ≥ 30 kg/m(2)) treated with a broad-spectrum β-lactam in whom therapeutic drug monitoring was performed and compared the data to those obtained in critically nonobese patients (body mass index of <25 kg/m(2)) to assess whether there were differences in reaching optimal drug concentrations for the treatment of nosocomial infections. Sixty-eight serum levels were obtained from 49 obese patients. There was considerable variability in β-lactam serum concentrations (coefficient of variation of 50% to 92% for the three drugs). Standard drug regimens of β-lactams resulted in insufficient serum concentrations in 32% of the patients and overdosed concentrations in 25%. Continuous renal replacement therapy was identified by multivariable analysis as a risk factor for overdosage and a protective factor for insufficient β-lactam serum concentrations. The serum drug levels from the obese cohort were well matched for age, gender, renal function, and sequential organ failure assessment (SOFA) score to 68 serum levels measured in 59 nonobese patients. The only difference observed between the two cohorts was in the subgroup of patients treated with meropenem and who were not receiving continuous renal replacement therapy: serum concentrations were lower in the obese cohort. No differences were observed in pharmacokinetic variables between the two groups. Routine therapeutic drug monitoring of β-lactams should be continued in obese critically ill patients.