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

Liquid chromatography with tandem mass spectrometric method for determination of 52 antibiotics in human whole blood and urine and application to forensic cases

PURPOSE

A rapid and reliable method was developed and validated for the simultaneous analysis of 52 antibiotics (cephalosporins, penicillins, carbapenems, lincosamides, quinolones, nitroimidazoles, macrolides, sulfonamides, tetracyclines, glycopeptide) in urine and whole blood by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS).

METHOD

Analytes were extracted by dilution or protein precipitation and analyzed on an Agilent 1260 HPLC system coupled to an Agilent 6470 Triple Quadrupole Mass Spectrometer.

RESULTS

The method attended method validation criteria. The limits of detection were equal or lower than 2.0 ng/mL, whereas the limits of quantification ranged from 0.1 to 10.0 ng/mL, from 0.1 to 5.0 ng/mL, in urine and whole blood, respectively. For all analytes, the bias and intra- and inter-day precision values were less than 14.7%. The ranges of recovery values of all antibiotics were 76.5-124.5% in whole blood and 76.3-121.8% in urine, values of the effects were lower than 25% in two matrices. No evidence of carryover was observed. The study of sample stability showed that almost all analytes were stable at 24 °C for 24 h, all analytes were stable at -20 °C for 14 days and at -80 °C for 30 days. Freeze-thaw cycles stability showed that antibiotics were stable except for imipenem. Autosampler stability study showed that all analytes were stable for 24 h, except for imipenem and amoxicillin. Applicability was proven by analyzing authentic whole blood (n = 86) and urine (n = 79) samples from patients under antibiotics treatment. Therefore, this method was applied to the analysis 3 forensic allergy cases, which were positive for at least one analyte.

CONCLUSIONS

A simple, sensitive and high-throughput method for the simultaneous determination of different classes of antibiotics in urine and whole blood samples was developed and applied. This sensitive method was successfully applied to forensic cases.

Development and Validation of a Capillary Zone Electrophoresis-Tandem Mass Spectrometry Method for Simultaneous Quantification of Eight β-Lactam Antibiotics and Two β-Lactamase Inhibitors in Plasma Samples

Monitoring plasma concentrations of β-lactam antibiotics is crucial, particularly in critically ill patients, where variations in concentrations can lead to treatment failure or adverse events. Standardized antimicrobial regimens may not be effective for all patients, especially in special groups with altered physiological parameters. Pharmacokinetic/pharmacodynamic (PK/PD) studies highlight the time-dependent antibacterial activity of these antibiotics, emphasizing the need for personalized dosing. Therapeutic drug monitoring (TDM) is essential, requiring rapid and accurate analytical methods for precise determination of drugs in biological material (typically plasma or serum). This study presents a novel capillary zone electrophoresis-tandem mass spectrometry (CZE-MS/MS) method designed for the simultaneous quantification of five penicillin antibiotics, two cephalosporins, one carbapenem, and two β-lactamase inhibitors in a single run. The method involves a simple sample pretreatment-precipitation with organic solvent-and has a run time of 20 min. Optimization of CZE separation conditions revealed that 20 mM ammonium hydrogen carbonate (NH4HCO3) serves as the optimal background electrolyte (BGE). Positive electrospray ionization (ESI) mode, with isopropyl alcohol (IP)/10 mM ammonium formate water solution (50/50, v/v) as the sheath liquid, was identified as the optimal condition for MS detection. Method validation according to the Food and Drug Administration (FDA) guideline for development of bioanalytical methods demonstrated satisfactory selectivity, linearity, recovery, robustness, and stability. The method's practicality was evaluated using the Blue Applicability Grade Index (BAGI), yielding a score of 77.5. Moreover, the greenness of the proposed method was evaluated by two commonly used metric tools-Analytical GREEnness (AGREE) and Green Analytical Procedure Index (GAPI). The developed CZE-MS/MS method offers a practical and reliable approach for quantifying a broad spectrum of β-lactam antibiotics in plasma. Its ability to simultaneously quantify multiple analytes in a single run, coupled with a straightforward sample pretreatment, positions it as a valuable and prospective tool for TDM in critically ill patients.

Liquid chromatography-tandem mass spectrometry methods for quantification of total and free antibiotic concentrations in serum and exudate from patients with post-sternotomy deep sternal wound infection receiving negative pressure wound therapy

BACKGROUND

Systemically administered antibiotics are thought to penetrate the wounds more effectively during negative pressure wound therapy (NPWT).To test this hypothesis total and free antibiotic concentrations were quantified in serum and wound exudate.

METHODS

UHPLC-MS/MS methods were developed and validated for the determination of ceftazidime, cefepime, cefotaxime, cefuroxime, cefazolin, meropenem, oxacillin, piperacillin with tazobactam, clindamycin, ciprofloxacin, sulfamethoxazole/trimethoprim (cotrimoxazole), gentamicin, vancomycin, and linezolid. The unbound antibiotic fraction was obtained by ultrafiltration using a Millipore Microcon-30kda Centrifugal Filter Unit. Analysis was performed on a 1.7-µm Acquity UPLC BEH C18 2.1 × 100-mm column with a gradient elution.

RESULTS

The validation was performed for serum, exudates and free fractions. For all matrices, requirements were met regarding linearity, precision, accuracy, limit of quantitation, and matrix effect. The coefficient of variation was in the range of 1.2-13.6%.and the recovery 87.6-115.6%, respectively. Among the 29 applications of antibiotics thus far, including vancomycin, clindamycin, ciprofloxacin, oxacillin, cefepime, cefotaxime, cotrimoxazole, and gentamicin, total and free antibiotic concentrations in serum and exudate were correlated.

CONCLUSION

This method can accurately quantify the total and free concentrations of 16 antibiotics. Comparison of concentration ratios between serum and exudates allows for monitoring individual antibiotics' penetration capacity in patients receiving NPWT.

Simultaneous determination of oxacillin and cloxacillin in plasma and CSF using turbulent flow liquid chromatography coupled to high-resolution mass spectrometry: Application in therapeutic drug monitoring

Cloxacillin and oxacillin are group M penicillins. The therapeutic monitoring of plasma concentrations of these antibiotics and those of their hydroxymethylated metabolites is of great clinical interest, especially in the choice of an adequate dosage allowing an effective treatment while limiting the occurrence of undesirable effects and the development of bacterial resistance. In this context, we conducted this work aiming at developing and validating a method allowing the determination of cloxacillin and oxacillin as well as the identification of their active metabolites in different biological matrices (CSF and plasma) using turbulent flow liquid chromatography coupled to high-resolution mass spectrometry. To do this, we carried out several optimisation tests. Subsequently, we validated our method according to the latest bioanalytical validation recommendations of the European Medicines Agency. The validation results showed that our method is specific and sensitive. We obtained good linearity in the range 0.5 to 100 µg/mL with correlation coefficients above 0.995. The lower limit of quantification was 0.5 µg/mL for each analyte. The method was found to be accurate with repeatability and reproducibility coefficients of variation below 15 %. Our method is also accurate with bias values below 15 %. Recovery values ranged from 87 % to 95 %. Finally, we were able to apply our method to the therapeutic monitoring of the analysed molecules and to identify their active metabolites. Our results suggest that LC-MS shows superiority in the therapeutic monitoring of these antibiotics due to the superiority of specificity shown by this method. This assay method can be routinely used for the daily plasma assays of patients treated with these antibiotics in the context of therapeutic monitoring.

Evaluating the heart valve tissue diffusion of amoxicillin in infective endocarditis: a pilot prospective observational non-comparative study

OBJECTIVES

Treating patients with infective endocarditis (IE) due to streptococci and enterococci currently involves high-dosage antibiotics. Recent literature suggests a 30%-70% diffusion rate could be extrapolated to human heart valve tissue. The objective of this study was to evaluate the diffusion coefficient of amoxicillin in heart valve tissue of patients operated for IE.

METHODS

Adult patients were prospectively included that underwent surgery at the European Hospital Georges Pompidou for IE due to streptococci and enterococci and had previous IV amoxicillin treatment. Plasma (taken 48 h preoperatively) and heart valve tissue amoxicillin concentrations were measured with a validated LC-MS/MS method. The MIC values of amoxicillin were measured for all available isolates.

RESULTS

Seventeen patients were included. Eleven (64.7%) patients had native valve IE and six (35.3%) had prosthetic valve IE. Fourteen IE cases (82.4%) were due to streptococci, one (5.9%) was due to enterococci and two (11.8%) were Haemophilus spp, Aggregatibacter actinomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens, Kingella kingae group infections. Median (IQR) amoxicillin dose administered was 10.5 (8.0-12.0) g/day corresponding to 138.2 (112.5-160.0) mg/kg/day. The median amoxicillin plasma concentrations pre-surgery and intra-tissular weighted concentrations were 31.9 (25.9-51.9) mg/L and 19.0 (7.9-31.4) µg/g, respectively. Median tissue/plasma concentration ratio was 0.47 (0.24-0.67), with a median amoxicillin plasma/MIC ratio of 487 (179-745), and median amoxicillin tissue/MIC ratio of 42 (14-116).

CONCLUSIONS

With a significant diffusion coefficient, amoxicillin dosage in heart valve tissues showed a concentration/MIC ratio well above current recommendations for bactericidal activity. Our study suggests that lower doses can be considered for susceptible bacteria.

Facile synthesis and eco-friendly analytical methods for concurrent estimation of selected pharmaceutical drugs in their solutions: application to quality by design, lean six sigma, and stability studies

Economical, highly robust, selective, precise, and eco-friendly RP-UPLC and spectrophotometric methods were developed and validated for the concurrent estimation of selected pharmaceutical drugs represented in ceftazidime (CFZ) and pyridine (PYD) in their solutions using Agilent Zorbax SB-C18 RRHD (50 × 2.1 mm, 1.8 μm) column at flow rate 0.3 mL/min with wavelength 254 nm. Box-Behnken design (BBD) established Response surface methodology (RSM) to achieve the optimum chromatographic condition with minimal trials conducted. Three independent variables specifically acetonitrile ratio 60-70%, pH 3-7, and temperature 25-35 °C were implemented to evaluate the influences of these variables on the responses as resolution and retention time. Desirability and overlay plots were carried out to adjust the optimal condition that achieved the shortest retention time of less than 2 min and desired resolution of more than 1.5 using a mobile phase consisting of acetonitrile: purified water (70:30, v/v) at pH 5.0 adjusted by 0.1% orthophosphoric acid with the column oven temperature 30 °C and column void volume 0.46 mL. Mean centering of ratio spectra (MCR) and ratio subtraction (RS) methods were effectively applied to resolve drugs' spectral superposition at 220 nm, 255.4 nm, 260.3 nm, and 254.6 nm for CFZ and PYD, respectively. Linearity range was accomplished for UPLC, MCR, and RS methods over the concentration range of 2-100, 1-50,3-30 and 5-30 µg/mL for CFZ and PYD, respectively with correlation coefficient > 0.999 and good recovery results within 98-102%. Six Sigma methodology was achieved using the process capability index (Cpk) to compare the suggested and USP methods showing that both are highly capable with Cpk > 1.33. The proposed method was successfully validated depending on ICH guidelines and ANOVA results and applied for the accelerated stability study.

Green Multiplex Chromatographic Determination of Nine Penicillin Antibiotics Residues in Industrial Air Dust and Wastewater Environmental Samples

Determination of penicillin residues in different industrial effluents including wastewater and air samples is important to prevent exposure to residual amounts of penicillin and the development of antibiotic resistance. A green high performance liquid chromatography (HPLC) method coupled with diode array detection has been developed and validated for multiplex determination of nine penicillin antibiotics in the industrial air dust and wastewater environmental samples of penicillin facility in addition to the monitoring of facility surface cleaning. Separation was performed on C18 column with gradient elution of methanol and phosphate buffer (pH 4) at a flow rate of 1.5 mL min-1 and ultra violet (UV) detection at 220 nm. Low limits of detection were achieved (0.1-0.3 μg mL-1) indicating good sensitivity of the proposed. The method was applied for ensuring the efficiency of cleaning validation after worst-case selection. Recovery studies of the studied penicillins from fortified stainless steel and polycarbonate surfaces and swabs were between 91.91 and 100.22% with relative standard deviation 0.11-1.79%. The presence of any of the studied penicillins in wastewater samples from penicillin plant drainage was checked. Also, total air dust concentration (mg m-3) and % of penicillin active material residues in air dust were calculated from the area of the exposed group in suspension, tablet and vial production lines. The proposed method can be recommended for routine analysis of air and wastewater environmental samples for the detection of penicillin antibiotics at low levels as well as monitoring of facility surface cleaning with high accuracy and precision.

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.

A liquid chromatography-tandem mass spectrometry method for the quantification of ampicillin/sulbactam and clindamycin in jawbone, plasma, and platelet-rich fibrin: Application to patients with osteonecrosis of the jaw

Ampicillin in combination with sulbactam is a widely used drug choice for infection prophylaxis, especially in oral and maxillofacial surgery. Clindamycin serves as an alternative in patients with known allergy to β-lactam antibiotics. To ensure effective prophylaxis, it is important to achieve sufficiently high concentrations of active antibiotic substances in the tissues affected by the surgery. To this end, a LC-MS/MS method was developed and validated that allows the quantification of ampicillin, sulbactam and clindamycin in jawbone, plasma, and so-called platelet-rich fibrin (PRF). Validation was performed in accordance with the European Medicines Agency guidelines for bioanalytical method validation. For all matrices, sample processing was carried out by protein precipitation with acetonitrile or methanol 80%, containing the isotope labelled internal standards (IS) of the three drugs. Analytes were separated on a pentaflourophenyl column at 20 °C using gradient elution. Furthermore, detection was accomplished by electrospray ionisation in positive-ion mode (ampicillin, clindamycin and corresponding IS) and negative-ion mode (sulbactam and corresponding IS) in combination with multiple reaction monitoring. Depending on the analyte and the matrix under investigation, calibration curves ranged from 0.14 to 59.8 µg/g (jawbone - ampicillin), 2.0-1000 µg/mL (plasma - ampicillin), and 1.0-495 µg/mL (PRF - ampicillin). All analytes fulfilled the requirements of the guideline regarding sensitivity, linearity, selectivity, carryover, within-run and between run accuracy and precision, matrix effect and extraction recovery in all matrices. The method was successfully applied to measure concentrations of ampicillin, sulbactam and clindamycin in real-life samples obtained in routine clinical 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.

Development and validation of an LC-ESI-QTOF-MS method to measure cefepime in the plasma and peritoneal fluid of rats using microdialysis: application in a pilot pharmacokinetic study

Cefepime (CEF) is a cephalosporin and can be administered in secondary peritonitis together with metronidazole to treat sepsis. This study aimed to develop and validate a method of LC-ESI-QTOF-MS for the quantification of cefepime in the plasma and peritoneal microdialysate of healthy Wistar rats. Chromatographic separation was performed using a CLC-ODS C₁₈ column (250 mm x 4.6 mm), a C₁₈ pre-column (4 mm, 5 μm) and isocratic elution. Gallic acid was used as the internal standard (IS). The mobile phase consisted of (A) ultrapure water (pH adjusted to 3.5) and (B) acetonitrile (80:20, v/v) at 0.8 mL/min. Quantification was performed using a mass spectrometer with electrospray ionization in positive mode to monitor ions with m/z 481.1322 (CEF) and m/z 171.0288 (IS). The method was validated for selectivity, precision, accuracy, linearity, stability, lower limit of quantification, carryover, recovery, and matrix effect. Calibration was done in the range of 1-40 μg/mL and 1-100 μg/mL for the peritoneal microdialysate and plasma, respectively. Plasma extraction recovery ranged from 93.9% to 99.9%. The technique was validated and successfully applied in a pilot pharmacokinetic study for estimating the free concentration of CEF in the peritoneal microdialysate of rats for the first time.

Detection of Oxytetracycline Using an Electrochemical Label-Free Aptamer-Based Biosensor

One of the most effective ways to detect and measure antibiotics is to detect their biomarkers. The best biomarker for the control and detection of oxytetracycline (OTC) is the OTC-specific aptamer. In this study, a novel, rapid, and label-free aptamer-based electrochemical biosensor (electrochemical aptasensor) was designed for OTC determination based on a newly synthesized nanocomposite including multi-walled carbon nanotubes (MWCNTs), gold nanoparticles (AuNPs), reduced graphene oxide (rGO), and chitosan (CS), as well as nanosheets to modify a glassy carbon electrode, which extremely enhanced electrical conductivity and increased the electrode surface to bind well with the amine-terminated OTC-specific aptamer through self-assembly. The (MWCNTs-AuNPs/CS-AuNPs/rGO-AuNPs) nanocomposite modified electrode was synthesized using a layer- by-layer modification method which had the highest efficiency for better aptamer stabilization. Differential pulse voltammetry (DPV), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM) techniques were used to investigate and evaluate the electrochemical properties and importance of the synthesized nanocomposite in different steps. The designed aptasensor was very sensitive for measuring the OTC content of milk samples, and the results were compared with those of our previously published paper. Based on the calibration curve, the detection limit was 30.0 pM, and the linear range was 1.00-540 nM for OTC. The repeatability and reproducibility of the aptasensor were obtained for 10.0 nM of OTC with a relative standard deviation (RSD%) of 2.39% and 4.01%, respectively, which were not affected by the coexistence of similar derivatives. The measurement in real samples with the recovery range of 93.5% to 98.76% shows that this aptasensor with a low detection limit and wide linear range can be a good tool for detecting OTC.

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

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

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.

Determination of ceftriaxone in human plasma using liquid chromatography-tandem mass spectrometry

Ceftriaxone is a cephalosporin antibiotic drug used as first-line treatment for a number of bacterial diseases. Ceftriaxone belongs to the third generation of cephalosporin and is available as an intramuscular or intravenous injection. Previously published pharmacokinetic studies have used high-performance liquid chromatography coupled with ultraviolet detection (HPLC-UV) for the quantification of ceftriaxone. This study aimed to develop and validate a bioanalytical method for the quantification of ceftriaxone in human plasma using liquid chromatography followed by tandem mass spectrometry (LC-MS/MS). Sample preparation was performed by protein precipitation of 100 µl plasma sample in combination with phospholipid-removal techniques to minimize matrix interferences. The chromatographic separation was performed on an Agilent Zorbax Eclipse Plus C18 column with 10 mM ammonium formate containing 2% formic acid: acetonitrile as mobile phase at a flow rate of 0.4 ml/min with a total run time of 10 minutes. Both the analyte and cefotaxime (internal standard) were detected using the positive electrospray ionization (ESI) mode and selected reaction monitoring (SRM) for the precursor-product ion transitions m/z 555.0→396.1 for ceftriaxone and 456.0→324.0 for cefotaxime. The method was validated over the concentration range of 1.01-200 μg/ml. Calibration response showed good linearity (correlation coefficient > 0.99) and matrix effects were within the ±15% limit in 6 different lots of sodium heparin plasma tested. However, citrate phosphate dextrose plasma resulted in a clear matrix enhancement of 24% at the low concentration level, which was not compensated for by the internal standard. Different anticoagulants (EDTA, heparin and citrate phosphate dextrose) also showed differences in recovery. Thus, it is important to use the same anticoagulant in calibration curves and clinical samples for analysis. The intra-assay and inter-assay precision were less than 5% and 10%, respectively, and therefore well within standard regulatory acceptance criterion of ±15%.

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.

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

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

Therapeutic Drug Monitoring of Antibiotic Drugs: The Role of the Clinical Laboratory

BACKGROUND

Therapeutic drug monitoring (TDM) of anti-infective drugs is an increasingly complex field, given that in addition to the patient and drug as 2 usual determinants, its success is driven by the pathogen. Pharmacodynamics is related both to the patient (toxicity) and bacterium (efficacy or antibiotic susceptibility). The specifics of TDM of antimicrobial drugs stress the need for multidisciplinary knowledge and expertise, as in any other field. The role and the responsibility of the laboratory in this interplay are both central and multifaceted. This narrative review highlights the role of the clinical laboratory in the TDM process.

METHODS

A literature search was conducted in PubMed and Google Scholar, focusing on the past 5 years (studies published since 2016) to limit redundancy with previously published review articles. Furthermore, the references cited in identified publications of interest were screened for additional relevant studies and articles.

RESULTS

The authors addressed microbiological methods to determine antibiotic susceptibility, immunochemical and chromatographic methods to measure drug concentrations (primarily in blood samples), and endogenous clinical laboratory biomarkers to monitor treatment efficacy and toxicity. The advantages and disadvantages of these methods are critically discussed, along with existing gaps and future perspectives on strategies to provide clinicians with as reliable and useful results as possible.

CONCLUSIONS

Although interest in the field has been the driver for certain progress in analytical technology and quality in recent years, laboratory professionals and commercial providers persistently encounter numerous unresolved challenges. The main tasks that need tackling include broadly and continuously available, easily operated, and cost-effective tests that offer short turnaround times, combined with reliable and easy-to-interpret results. Various fields of research are currently addressing these features.

Quantification of 15 Antibiotics Widely Used in the Critical Care Unit with a LC-MS/MS System: An Easy Method to Perform a Daily Therapeutic Drug Monitoring

Potential under- or overdose of antibiotics may occur in intensive care units due to high variability in plasma concentrations. The risk is either treatment failure or toxicity. Thus, therapeutic drug monitoring of antibiotics may guide dosing adjustment, maximising antibacterial efficacy and minimising toxicity. The aim of this study was to develop and validate a method for the analysis of 15 antibiotics including beta-lactams, linezolid, fluoroquinolones, daptomycin, and clindamycin to have a complete panel in the management of infections. We proposed to develop a fast, sensitive, and quantitative method for the analysis of 15 antibiotics using ultra-performance liquid chromatography coupled with triple quadrupole mass spectrometer (UPLC-MS/MS) technology. this method required only 100 µL of plasma and consisted of a rapid liquid-liquid deproteinisation using methanol. Calibration curves ranged from 0.078 to 500 mg/L depending on the molecules, and were defined according to a therapeutic range. Inter- and intra-assay precisions values were less than 15%. This work described the development and the full validation of a precise, sensitive and accurate assay using UPLC-MS/MS technology. After validation, this new assay was successfully applied to routine therapeutic drug monitoring.

Determination of ceftriaxone in human plasma using liquid chromatography–tandem mass spectrometry

Ceftriaxone is a cephalosporin antibiotic drug used as first-line treatment for a number of bacterial diseases. Ceftriaxone belongs to the third generation of antibiotics and is available as an intramuscular or intravenous injection. Previously published pharmacokinetic studies have used high-performance liquid chromatography coupled with ultraviolet detection (HPLC-UV) for the quantification of ceftriaxone. This study aimed to develop and validate a bioanalytical method for the quantification of ceftriaxone in human plasma using liquid chromatography followed by tandem mass spectrometry (LC-MS/MS). Sample preparation was performed by protein precipitation of 100 µl plasma sample in combination with phospholipid-removal techniques to minimize matrix interferences. The chromatographic separation was performed on an Agilent Zorbax Eclipse Plus C18 column with 10 mM ammonium formate containing 2% formic acid: acetonitrile as mobile phase at a flow rate of 0.4 ml/min with a total run time of 10 minutes. Both the analyte and cefotaxime (internal standard) were quantified using the positive electrospray ionization (ESI) mode and selected reaction monitoring (SRM) for the precursor-product ion transitions m/z 555.0→396.1 for ceftriaxone and 456.0→324.0 for cefotaxime. The method was validated over the concentration range of 1.01-200 μg/ml. Calibration response showed good linearity (correlation coefficient > 0.99) and matrix effects were within the ±15% limit in 6 different lots of sodium heparin plasma tested. However, citrate phosphate dextrose plasma resulted in a clear matrix enhancement of 24% at the low concentration level, which was not compensated for by the internal standard. Different anticoagulants (EDTA, heparin and citrate phosphate dextrose) also showed differences in recovery. Thus, it is important to use the same anticoagulant in calibration curves and clinical samples for analysis. The intra-assay and inter-assay precision were less than 5% and 10%, respectively, and therefore well within standard regulatory acceptance criterion of ±15%.

Meropenem Stability in Human Plasma at -20 °C: Detailed Assessment of Degradation

There are concerns about the stability of meropenem in plasma samples, even when frozen at −20 °C. Previous smaller studies suggested significant degradation of meropenem at −20 °C after 3–20 days. However, in several recent clinical studies, meropenem plasma samples were still stored at −20 °C, or the storage temperature and/or time were not mentioned in the paper. The aim of this study was to describe and model meropenem degradation in human plasma at −20 °C over 1 year. Stability of meropenem in human plasma at −20 °C was investigated at seven concentrations (0.44, 4.38, 17.5, 35.1, 52.6, 70.1, and 87.6 mg/L) representative for the range of relevant concentrations encountered in clinical practice. For each concentration, samples were stored for 0, 7, 14, 21, 28, 42, 56, 70, 84, 112, 140, 168, 196, 224, 252, 280, 308, 336, and 364 days at −20 °C before being transferred to −80 °C until analysis. Degradation was modeled using polynomial regression analysis and artificial neural network (ANN). Meropenem showed significant degradation over time in human plasma when stored at −20 °C. Degradation was present over the whole concentration range and increased with higher concentrations until a concentration of 35.1 mg/L. Both models showed accurate prediction of meropenem degradation. In conclusion, this study provides detailed insights into the concentration-dependent degradation of meropenem in human plasma stored at −20 °C over 1 year. Meropenem in human plasma is shown to be stable at least up to approximately 80 days when stored at −20 °C. The polynomial model allows calculating original meropenem concentrations in samples stored for a known period of time at −20 °C.

Quantitation using HRMS: A new tool for rapid, specific and sensitive determination of catecholamines and deconjugated methanephrines metanephrines in urine

Urinary catecholamines and their methylated metabolites are biochemical indicators of pheochromocytoma, paraganglioma and neuroblastoma. A rapid and precise analytical method based on solid-phase extraction (SPE) and liquid chromatography separation coupled to high-resolution mass spectrometry (LC-HRMS) was developed and validated to measure urinary catecholamines (epinephrine (E), norepinephrine (NorE), dopamine (D)) and total methylated metabolites (normetanephrine (NorMN), metanephrine(MN) and 3-methoxytyramine (3-MT)) in a clinical setting. Results of 51 urine specimens measured using this LC-HRMS method were compared with a liquid chromatography assay with electrochemical detection (LC-EC). Urine samples (200 μL) were spiked with an internal standard solution followed by SPE purification. In the case of total methylated metabolites, urine was hydrolyzed before SPE purification. Separation was achieved on an Acclaim Mixed Mode WCX column, with an 8.5 min runtime. All compounds were detected in electrospray positive ionization mode with a parallel reaction monitoring acquisition and quantified with a linear regression (r2 > 0.998) between 2 and 200 µg/L (10.9-1090; 11.8-1182 nmol/L) for E and NorE respectively and between 10 and 1000 µg/L for others (65.2-6520; 50.7-5070; 54.5-5450 ; 59.8-5980 nmol/L for D, M, NorMN and 3-MT, respectively). Overall imprecision and bias did not exceed 15%. No significant matrix effect was observed. Correlation between the two assays was good except for epinephrine. Epinephrine concentrations measured by LC-EC method were slightly higher than values obtained with LC-HRMS method but without impact on clinical decision. This LC-HRMS assay provides a new tool for simultaneous quantitative catecholamine determination and was successfully applied in routine for the screening or follow up of pheochromocytoma, paraganglioma and neuroblastoma. LC-HRMS method offers significant advantages compared to LC-EC with good sensitivity, an unambiguous analyte determination and high sample throughput.

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.

An Oral FMT Capsule as Efficient as an Enema for Microbiota Reconstruction Following Disruption by Antibiotics, as Assessed in an In Vitro Human Gut Model

Fecal microbiota transplantation (FMT) is an innovative therapy already used in humans to treat Clostridioides difficile infections associated with massive use of antibiotics. Clinical studies are obviously the gold standard to evaluate FMT efficiency but remain limited by regulatory, ethics, and cost constraints. In the present study, an in vitro model of the human colon reproducing medically relevant perturbation of the colonic ecosystem by antibiotherapy was used to compare the efficiency of traditional FMT enema formulations and a new oral capsule in restoring gut microbiota composition and activity. Loss of microbial diversity, shift in bacterial populations, and sharp decrease in fermentation activities induced in vivo by antibiotherapy were efficiently reproduced in the in vitro model, while capturing inter-individual variability of gut microbiome. Oral capsule was as efficient as enema to decrease the number of disturbed days and bacterial load had no effect on enema performance. This study shows the relevance of human colon models as an alternative approach to in vivo assays during preclinical studies for evaluating FMT efficiency. The potential of this in vitro approach could be extended to FMT testing in the management of many digestive or extra-intestinal pathologies where gut microbial dysbiosis has been evidenced such as inflammatory bowel diseases, obesity or cancers.

Direct infusion nano-electrospray ionization mass spectrometry for therapeutic drug monitoring of ciprofloxacin and its metabolites in human saliva

A rapid and sensitive method based on direct infusion-nano-electrospray ionization mass spectrometry (DI-nESI-MS) has been developed for the detection and quantification of ciprofloxacin and its metabolites in human saliva. Saliva samples were collected after the oral administration of 500 mg ciprofloxacin tablets. Internal standard (IS), tamoxifen, was added to the collected samples, and then diluted with the ionization solvent, centrifuged and filtered. An aliquot of 4 μL of the filtrate was loaded into a nanospray (NS) capillary. The NS capillary was then fitted into an off-line ion source and the instrument was operated to acquire a two-minute run by applying a voltage of 1000 V (positive-ion detection mode). Quantification of ciprofloxacin relied on the ratio of its peak intensity to the IS peak intensity. The DI-nESI-MS method was validated and provided satisfactory precision with relative standard deviation ranging from 0.39 to 7.48 % and accuracy with relative error ranging from -2.12 to 9.72 %. The calibration curve showed good linearity (r²) > 0.999 over the concentration range of 10-4000 ng/mL. These results verify the effectiveness of the DI-nESI-MS method for monitoring of ciprofloxacin and its metabolites in human saliva samples.

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.

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.

Simultaneous determination of six antibiotics in human serum by high-performance liquid chromatography with UV detection

Antibiotics are widely used in intensive care patients to treat severe infections. To avoid bacterial resistance or toxic side effects, the determination of serum concentration of ABs is advisable. Therefore, in this study, we developed and validated a simple and fast high-performance liquid chromatography method with UV detection for the simultaneous determination of four β-lactam ABs (meropenem, imipenem, ceftazidime, and piperacillin) and two coadministered substances (cilastatin and tazobactam) in human serum. Sample preparation required a simple protein precipitation by methanol. The separation of the ABs occurred within a timeframe of 17 min. For this purpose, we used a Kinetex F5 column with a linear gradient of acetonitrile and phosphate buffer (pH 6.9). The UV detector recorded two separate chromatograms at 220 and 295 nm simultaneously. Validation has demonstrated that the method is linear, accurate, and precise within the clinically relevant range for each substance.

Ceftriaxone pharmacokinetics by a sensitive and simple LC-MS/MS method: Development and application

Ceftriaxone is a third-generation cephalosporin, worldwide use as a first-line treatment for several infections, including life-threatening infections as meningitis or endocarditis. Nowadays, ceftriaxone use is changing, embracing high-dose schemes, new populations treated and requirement of dose individualization and optimization. These reasons warranted the development of new sensitive assays. This study aimed to develop and validate a fast and handy bioanalytical method for the quantification of ceftriaxone in human plasma covering a broad range of concentrations. The analysis was performed using high-performance liquid chromatography coupled to tandem mass spectrometry. Sample preparation was based on protein precipitation with acetonitrile followed by centrifugation. Chromatography separation was performed on Phenomenex Luna C18 column (5 μm, 150 × 2.0 mm) and a mobile phase consisting of 70 % of mobile phase A (10 mM of ammonium acetate and 1% formic acid in purified water) and 30 % mobile phase B (0.1 % formic acid in acetonitrile) at a flow rate of 500 μl/min on an isocratic program. Both the analyte and the internal standard were quantified using the positive electrospray ionization (ESI) mode within a single runtime of 5.00 min. The method was validated following the U.S. Food and Drug Administration guidelines over the concentration range of 3-1000 μg/mL. The within-run and between-run precision and accuracy were <15 %, and therefore met the standard regulatory acceptance criterion. In conclusion, a sensitive and robust LC-MS/MS method was developed for a fast quantitation of ceftriaxone concentrations in plasma samples with multiples applications in research and clinical therapeutic drug monitoring.

Europium chelate-labeled lateral flow assay for rapid and multiple detection of β-lactam antibiotics by the penicillin-binding protein

For the multiple and rapid detection of β-lactams, the broadly specific penicillin-binding protein (PBP) that recognizes the β-lactam structure was prepared. A chromatographic strip based on europium chelate-loaded fluorescent microspheres was assembled with a goat anti-mouse antibody (C line) and penicillin coating (T line). The penicillin coating competes with free β-lactam antibiotics to bind PBP-labeled fluorescent microspheres. The strip can theoretically detect all kinds of β-lactams, including amoxicillin, ampicillin, oxacillin, ceftazidime, lenampicillin, cefoperazone, sultamicillin, cefotaxime, ceftriaxone, sulbenicillin, piperacillin, cephalothin, flucloxacillin, and mezlocillin, in samples within 10 min. The europium chelate-labeled lateral flow assay does not cross-react with other antibiotics, including chloramphenicol, tetracycline, sulfamethazine, enrofloxacin, gentamicin or lincomycin. In short, we developed a very useful method for preliminary screening of β-lactams.

Validation and clinical application of a multiplex high performance liquid chromatography - tandem mass spectrometry assay for the monitoring of plasma concentrations of 12 antibiotics in patients with severe bacterial infections

OBJECTIVE

Unpredictable pharmacokinetics of antibiotics in patients with life-threatening bacterial infections is associated with drug under- or overdosing. Therapeutic drug monitoring (TDM) may guide dosing adjustment aimed at maximizing antibacterial efficacy and minimizing toxicity. Rapid and accurate analytical methods are key for real-time TDM. Our objective was to develop a robust high-performance liquid chromatography-tandem mass spectrometry method (HPLC-MS/MS) for multiplex quantification of plasma concentrations of 12 antibiotics: imipenem/cilastatin, meropenem, ertapenem, cefepime, ceftazidime, ceftriaxone, piperacillin/tazobactam, amoxicillin, flucloxacillin, rifampicin, daptomycin.

METHODS

A single extraction procedure consisting in methanol plasma protein precipitation and H₂O dilution was used for all analytes. After chromatographic separation on an Acquity UPLC HSS-T3 2.1 × 50 mm, 1.8 µm (Waters®) column, quantification was performed by electro-spray ionisation-triple quadrupole mass spectrometry with selected reaction monitoring detection. Antibiotics were divided in two pools of calibration according to the frequency of analyses requests in the hospital routine antibiotic TDM program. Stable isotopically-labelled analogues were used as internal standards. A single analytical run lasted less than 9 min.

RESULTS

The method was validated based on FDA recommendations, including assessment of extraction yield (96-113.8%), matrix effects, and analytical recovery (86.3-99.6%). The method was sensitive (lower limits of quantification 0.02-0.5 µg/mL), accurate (intra/inter-assay bias -11.3 to +12.7%) and precise (intra/inter-assay CVs 2.1-11.5%) over the clinically relevant plasma concentration ranges (upper limits of quantification 20-160 µg/mL). The application of the TDM assay was illustrated with clinical cases that highlight the impact on patients' management of an analytical assay providing information with short turn-around time on antibiotic plasma concentration.

CONCLUSION

This simple, robust high-throughput multiplex HPLC-MS/MS assay for simultaneous quantification of plasma concentrations of 12 daily used antibiotics is optimally suited for clinically efficient real-time TDM.

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.

Determination of carbapenems in water samples by UHPLC-MS/MS

A rapid and reliable method for the detection of five carbapenems (biapenem, imipenem, doripenem, meropenem, and faropenem) in water was developed and validated. After acidification of water samples with acetic acid, carbapenems were isolated using a Bond Elut PPL cartridge. The target compounds were separated using ultra high performance liquid chromatography with a chromatographic run time of 5 min and detected on a triple quadrupole mass spectrometer operated in positive electrospray ionization and multiple reaction monitoring mode. Mean recoveries were in the range of 76.6-106.5%, with satisfactory intraday and interday relative standard deviations lower than 10.0 and 10.8%, respectively. The limits of detection and quantification were in the ranges of 0.05-0.2 µg/L and 0.1-0.5 µg/L, respectively, depending on the analyte. The proposed method was applied to the analysis of river samples and wastewater samples from swine farms, and no carbapenems were detected in the collected samples.

On-Site Therapeutic Drug Monitoring

Recent technological advances have stimulated efforts to bring personalized medicine into practice. Yet, traditional application fields like therapeutic drug monitoring (TDM) have remained rather under-appreciated. Owing to clear dose-response relationships, TDM could improve patient outcomes and reduce healthcare costs. While chromatography-based routine practices are restricted due to high costs and turnaround times, biosensors overcome these limitations by offering on-site analysis. Nevertheless, sensor-based approaches have yet to break through for clinical TDM applications, due to the gap between scientific and clinical communities. We provide a critical overview of current TDM practices, followed by a TDM guideline to establish a common ground across disciplines. Finally, we discuss how the translation of sensor systems for TDM can be facilitated, by highlighting the challenges and opportunities.

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.

Simple and reliable extraction and a validated high performance liquid chromatographic assay for quantification of amoxicillin from plasma

This study presents the development of an efficient extraction protocol for amoxicillin from plasma with improved solubility and stability using pH control. Solubility and stability of amoxicillin in commonly used extraction solvents were determined using a newly developed stability-indicating high-performance liquid chromatography (HPLC) method. Following this, protein precipitation (PP) mediated sample purification protocol was developed and validated along with the HPLC method for the extracted amoxicillin from rabbit plasma. The protocol was applied in a pharmacokinetic study in rabbits. A five-fold increase in solubility and two-fold increase in stability of amoxicillin was found by addition of acetate buffer (0.1 M, pH 5.0) in acetonitrile. PP mediated extraction protocol containing acetate buffer-acetonitrile (1:18 v/v) resulted in an extraction recovery of >80% for all the samples. The HPLC assay following extraction was found linear (R²   >0.9999) over the range of 0.2-20 µg/mL with a lower limit of quantification of 0.2 µg/mL. The accuracy of the quality control samples was found between 97-115% and the relative standard deviation (RSD) was found to be below 6% for all samples. The samples were stable in the mobile phase (pH 5.0) for 72 h post-extraction. Amoxicillin-spiked plasma samples were found stable for up to three freeze-and-thaw cycles but, nearly 50% samples had degraded following storage for two months at -20 °C. Pharmacokinetic analysis indicated a half-life of amoxicillin of nearly 1 h following intravenous injection in rabbits, which is similar to that in humans. Thus, a simple and repeatable, extraction protocol was developed using pH control for quantification of amoxicillin from plasma based on its physicochemical properties.

Liquid chromatography-tandem mass spectrometry for the simultaneous quantitation of enmetazobactam and cefepime in human plasma

A simple ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed and validated for the simultaneous analysis enmetazobactam (also known as AAI101) and cefepime in human plasma. Sample preparation was based on protein precipitation with acetonitrile. Separation was performed on Acquity BEH HILIC column (50 mm × 2.1 mm, 1.7 μm) with a mobile phase containing ammonium formate in water and acetonitrile. The analytes were analyzed with the corresponding isotopically labeled internal standards and were detected in multiple reactions monitoring (MRM) using API 5000 triple-quadrupole mass spectrometer with electrospray (ESI) source operating in positive ion mode. The calibration curves were linear over the selected ranges (r > 0.9970 for both analytes). The intra and inter-assay precision of the Quality Control samples showed CV ≤ 15% and the accuracy was within 85 and 115% in all cases for both compounds. The lower limit of quantification was 0.05 μg/mL for enmetazobactam and 0.5 μg/mL for cefepime.

Determination of ceftriaxone concentration in human cerebrospinal fluid by high-performance liquid chromatography with UV detection

Determination of ceftriaxone (CTRX) concentration in human cerebrospinal fluid (CSF) is required to clarify whether a high concentration of CTRX in CSF is associated with CTRX-induced encephalopathy (CIE). In our study, in order to perform an accurate analysis of CSF sample from CIE patient, we proposed HPLC with UV detection (HPLC-UV) using an octadecylsilica (ODS) column, a methanol and 10 mM phosphoric acid (25:75, v/v) mixture solution as a mobile phase, and a detection wavelength at 280 nm. The linear range was from 0.1 to 100 μg/mL (r = 0.999) in the present HPLC-UV. In the recovery tests using blank samples of human CSF and control serum spiked with CTRX, the recoveries of CTRX were >95.3%, and the RSD (n = 3) was <5.8%. We applied the proposed HPLC-UV system to determine CTRX in the CSF and serum samples obtained from a patient diagnosed as having CIE, and it was revealed that the CTRX concentrations in the CSF sample and the serum were 2.61 and 37.35 μg/mL, respectively. To the best of our knowledge, this is the first report describing the determination of CTRX concentration in a CSF sample obtained from a peritoneal dialysis patient diagnosed as having CIE.

Determination of Quinolone Antibiotic Residues in Human Serum and Urine Using High-Performance Liquid Chromatography/Tandem Mass Spectrometry

Quinolone antibiotic residues may pose potential threat to human health. A rapid and sensitive method was developed for the determination of quinolone residues in human serum and urine. After solid phase extraction (SPE) process, eight quinolone residues were analyzed by high-performance liquid chromatography/tandem mass spectrometry (HPLC-MS/MS) using ciprofloxacin-d8 as the internal standard. The relative standard deviation of intra-day and inter-day precision for the eight quinolones were less than 7.52% and the accuracies ranged from 95.8% to 103% in human serum, and from 94.1% to 104% in human urine. The extraction recoveries for the eight quinolones varied from 80.2% to 113% in human serum and 83.4% to 117% in human urine. The limit of detection for the eight quinolones was 0.50–1.00 ng/mL. Quinolone antibiotic residues in human serum and urine from 12 volunteers were successfully analyzed with the validated method. The SPE-HPLC-MS/MS method was useful for accurate determination of quinolone antibiotic residues in human body.