Simultaneous determination of cefepime, vancomycin and imipenem in human plasma of burn patients by high-performance liquid chromatography

Quantification of meropenem in serum and cerebrospinal fluid in children with bacterial meningitis with augmented renal clearance by UPLC-MS/MS

Meropenem is an ultrabroad-spectrum antimicrobial agent that is often recommended for the treatment of bacterial meningitis (BM) in children. However, a subtherapeutic phenomenon occurred in BM children complicated with augmented renal clearance (ARC) at the recommended dose of meropenem. To support its pharmacokinetics, a sensitive, fast and robust ultra-liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed to measure meropenem concentrations in serum and cerebrospinal fluid (CSF). The method involved protein precipitation, and samples were diluted with a large proportion of water to eliminate solvent effects. The separation of samples was performed on a Waters Acquity™ BEH C18 column (2.1 × 50 mm i.d., 1.7 μm) with a gradient profile. The mobile phases were formic acid-water (1:1000, v/v) and acetonitrile. The linear range was good, with a concentration range of 0.100-100 μg/mL for serum and 0.0400-20.0 μg/mL for CSF. The intra-day and inter-day precisions were less than 8.0%, and the intra-day and inter-day accuracies varied -6.6% from 6.5% for the both serum and CSF. The selectivity, carry-over, dilution integrity, matrix effect, recovery and stability were validated according to international guidelines. The developed UPLC-MS/MS method successfully determined the meropenem concentrations in the serum and CSF of children with BM complicated with ARC. The results indicated that under the recommended dosing regimen (40 mg/kg every 8 h), the time to reach the effective treatment target of 50%T > MIC was only approximately 3 h and lower CSF concentrations of meropenem were observed in children with BM with ARC.

Population pharmacokinetics and dosing optimisation of imipenem in critically ill patients

OBJECTIVE

The objective of this study was to explore factors that affect the clearance of imipenem in critically ill patients and to provide a dosing regimen for such patients.

METHODS

A prospective open-label study enrolled 51 critically ill patients with sepsis. Patients were between the ages of 18 and 96. Blood samples were collected in duplicate before (0 hour) and at 0.5, 1, 1.5, 2, 3, 4, 6, and 8 hours after imipenem administration. The plasma imipenem concentration was determined by the high-performance liquid chromatography-ultraviolet detection (HPLC-UV) method. A population pharmacokinetic (PPK) model was developed using nonlinear mixed-effects modelling methods to identify covariates. Monte Carlo simulations were performed using the final PPK model to explore the effect of different dosing regimens on the probability of target attainment (PTA).

RESULTS

The imipenem concentration data were best described by a two-compartment model. Creatinine clearance (CrCl, mL/min) was a covariate that affected central clearance (CLc). Patients were divided into four subgroups based on different CrCl rates. Monte Carlo simulations were performed to assess the PTA differences between empirical dosing regimens (0.5 g every 6 hours (q6h), 0.5 g every 8 hours (q8h), 0.5 g every 12 hours (q12h), 1 g every 6 hours (q6h), 1 g every 8 hours (q8h), and 1 g every 12 hours (q12h)) and to determine the target achievement rate covariate.

CONCLUSION

This study identified covariates for CLc, and the proposed final model can be used to guide clinicians administering imipenem in this particular patient population.

An Ultra-High-Performance Liquid Chromatography-Tandem Mass Spectrometry Method for Simultaneous Determination of 4 β-Lactam Antibiotics, Tazobactam, and Linezolid in Human Plasma Samples

BACKGROUND

Optimization of antimicrobial therapy is a challenge in critically ill patients who develop extreme interindividual and intraindividual pharmacokinetic variability. Therapeutic drug monitoring is a valuable tool for maximizing the effect of a drug and minimizing its adverse and unwanted effects. The aim of the current work was to develop and validate an ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method to determine multiple antibiotics in clinical plasma samples from critically ill patients; low sample volume and rapid processing of samples were considered the main criteria.

METHODS

A separation method based on an online combination of UHPLC-MS/MS was developed for the simultaneous determination of 4 β-lactam antibiotics (cefepime, meropenem, cefotaxime, and piperacillin), tazobactam, and linezolid in human plasma samples. The volume of plasma sample used for analysis was 20 µL. The developed method was validated according to Food and Drug Administration guidelines.

RESULTS

The chromatographic run time was 8 minutes. Calibration curves were linear for concentration ranges of 0.1-100 mcg/mL (r 2 > 0.99) for tazobactam, meropenem, cefotaxime, linezolid, and piperacillin and 1-100 mcg/mL (r 2 > 0.99) for cefepime. The intraday and interday accuracy of the method ranged from 92.4% to 110.7% and 93.6% to 113.3%, respectively. The intraday and interday precision values were ≤17.3% and ≤17.4%, respectively. No interfering and carryover analytes were observed.

CONCLUSIONS

The developed UHPLC-MS/MS method is an appropriate and practical tool for therapeutic drug monitoring of the selected antibiotics. Owing to its rapidity, requirement of low sample volume, and high selectivity, sensitivity, and reliability, it can be effectively implemented in routine clinical laboratory tests for critically ill patients.

An Overview of Analytical Methodologies for Determination of Vancomycin in Human Plasma

Vancomycin is regarded as the last resort of defense for a wide range of infections due to drug resistance and toxicity. The detection of vancomycin in plasma has always aroused particular concern because the performance of the assay affects the clinical treatment outcome. This article reviews various methods for vancomycin detection in human plasma and analyzes the advantages and disadvantages of each technique. Immunoassay has been the first choice for vancomycin concentration monitoring due to its simplicity and practicality, occasionally interfered with by other substances. Chromatographic methods have mainly been used for scientific research due to operational complexity and the particular requirement of the instrument. However, the advantages of a small amount of sample needed, high sensitivity, and specificity makes chromatography irreplaceable. Other methods are less commonly used in clinical applications because of the operational feasibility, clinical application, contamination, etc. Simplicity, good performance, economy, and environmental friendliness have been points of laboratory methodological concern. Unfortunately, no one method has met all of the elements so far.

Review on Characterization, Properties, and Analytical Methods of Cefepime

Infection is one of the most important reasons for the increase in the number of deaths worldwide; it can be a bacterial or viral infection. As a result, there are many effective drugs against this infection, especially bacterial ones. Cefepime (CP) is one of the fourth generations of cephalosporins and is distinguished from others in that it can kill both positive and negative bacteria. Therefore, this study focused on the chemical properties of the drug, its uses, and its stability against bacteria. All analysis methods for this drug in pharmaceutical preparations, blood, or plasma were also presented. One of the important problems in these methods is using toxic solvents, which poses a danger to society and the environment. The presentation of these solvents will allow companies to manufacture and use more effective and less toxic solvents.

Utility of Silver-nanoparticles for Nano-fluorimetric Determination of Vancomycin Hydrochloride in Pharmaceutical Formulation and Biological Fluids: Greenness Assessment

Vancomycin hydrochloride (VANH) is a glycopeptide antibiotic commonly employed in the prophylaxis and therapy of various gram-positive bacterial life-threatening infections. Due to the narrow therapeutic window of VANH, its serum levels should be well-monitored to avoid its toxicity and to optimize its therapy. Herein, an innovative silver-nanoparticles enhanced fluorescence technique was designed for VANH rapid analysis in its pharmaceutical formulation and biological fluids. This technique is based on reinforcement of VANH fluorescence intensity with silver-nanoparticles that were synthesized by a redox reaction between VANH and silver nitrate in NaOH alkaline medium using polyvinylpyrrolidone as a stabilizer. The produced silver-nanoparticles were characterized by using UV-visible spectroscopy where they have an intense absorption maximum at 415 nm and transmission electron microscope (TEM) micrograph where they are spherical in shape with smooth surface morphology and size of 10.74 ± 2.44 nm. The fluorescence intensity was measured at 394 nm after excitation at 259 nm. Under optimum conditions, a good linear relationship was accomplished between the VANH concentration and the fluorescence intensity in a range of (1-36) ng/mL with a limit of detection of 0.29 ng/mL. Greenness assessment was performed using two assessment tools namely; eco-scale scoring and green analytical procedure index revealing excellent greenness of the proposed technique. The proposed technique was validated according to the International Conference on Harmonisation (ICH) recommendations and statistically compared with the reported HPLC method revealing no significant difference concerning accuracy and precision at p = 0.05. The proposed technique depended primarily on water as a cheap and eco-friendly solvent.

Simultaneous determination of meropenem and imipenem in rat plasma by LC-MS/MS and its application to a pharmacokinetic study

An efficient and reliable method using LC-MS/MS was established and validated for the simultaneous quantification of meropenem and imipenem in rat plasma. An electronic spray ion source in the positive multiple reaction monitoring mode was used for the detection and the transitions were m/z 384.6 → m/z 141.2 for meropenem, m/z 300.1 → m/z 141.8 for imipenem and m/z 423.4 → m/z 207.1 for matrine (IS). The calibration curves of meropenem and imipenem were linear in the range of 0.50-200 μg/mL. Satisfactory separation was achieved with a total run time of 3.0 min, the injection volume was 3 μl. The retention times of meropenem, imipenem and IS were 1.19, 1.14 and 1.13 min, respectively. Meropenem and imipenem are easily hydrolyzed in plasma. HEPES was used as a stabilizer and added to the plasma samples immediately after centrifugation. Extractions of meropenem, imipenem and IS were carried out by protein precipitation with acetonitrile. The specificity, precision and accuracy, stability, recovery and matrix effects were within acceptance limits. This method was successfully applied to investigate the pharmacokinetics of intravenous injection of meropenem and imipenem single administration or combined with sulbactam in rats. We found that sulbactam has no influence on the pharmacokinetics behavior of meropenem or imipenem.

A systematic review on chromatography-based method validation for quantification of vancomycin in biological matrices

A fully validated bioanalytical methods are prerequisite for pharmacokinetic and bioequivalence studies as well as for therapeutic drug monitoring. Due to high pharmacokinetic variability and narrow therapeutic index, vancomycin requires reliable quantification methods for therapeutic drug monitoring. To identify published chromatographic based bioanalytical methods for vancomycin in current systematic review, PubMed and ScienceDirect databases were searched. The selected records were evaluated against the method validation criteria derived from international guidelines for critical assessment. The major deficiencies were identified in method validation parameters specifically for accuracy, precision and number of calibration and validation standards, which compromised the reliability of the validated bioanalytical methods. The systematic review enacts to adapt the recommended international guidelines for suggested validation parameters to make bioanalysis reliable.

Vancomycin for Dialytic Therapy in Critically Ill Patients: Analysis of Its Reduction and the Factors Associated with Subtherapeutic Concentrations

This study aimed to evaluate the reduction in vancomycin through intermittent haemodialysis (IHD) and prolonged haemodialysis (PHD) in acute kidney injury (AKI) patients with sepsis and to identify the variables associated with subtherapeutic concentrations. A prospective study was performed in patients admitted at an intensive care unit (ICU) of a Brazilian hospital. Blood samples were collected at the start of dialytic therapy, after 2 and 4 h of treatment and at the end of therapy to determine the serum concentration of vancomycin and thus perform pharmacokinetic evaluation and PK/PD modelling. Twenty-seven patients treated with IHD, 17 treated with PHD for 6 h and 11 treated with PHD for 10 h were included. The reduction in serum concentrations of vancomycin after 2 h of therapy was 26.65 ± 12.64% and at the end of dialysis was 45.78 ± 12.79%, higher in the 10-h PHD group, 57.70% (40, 48–64, 30%) (p = 0.037). The ratio of the area under the curve to minimal inhibitory concentration (AUC/MIC) at 24 h in the PHD group was significantly smaller than at 10 h (p = 0.047). In the logistic regression, PHD was a risk factor for an AUC/MIC ratio less than 400 (OR = 11.59, p = 0.033), while a higher serum concentration of vancomycin at T0 was a protective factor (OR = 0.791, p = 0.009). In conclusion, subtherapeutic concentrations of vancomycin in acute kidney injury (AKI) patients in dialysis were elevated and may be related to a higher risk of bacterial resistance and mortality, besides pointing out the necessity of additional doses of vancomycin during dialytic therapy, mainly in PHD.

Pharmacokinetic and Pharmacodynamic Analysis of Critically Ill Patients Undergoing Continuous Renal Replacement Therapy With Imipenem

PURPOSE

This study explores factors that affect behavior in critically ill patients receiving continuous renal replacement therapy (CRRT) with imipenem and provides dosing regimens for these patients.

METHODS

A prospective, open-label study was conducted in a clinical setting. Both blood and effluent samples were collected pairwise at the scheduled time points. Plasma and effluent imipenem concentrations were determined by HPLC-UV. A population pharmacokinetic model was developed using a nonlinear mixed-effects modeling method. The final model was evaluated by a bootstrap and visual predictive check. A population pharmacokinetic and pharmacodynamic analysis using Monte Carlo simulations was performed to explore the effects of empirically used dosing regimens (0.5 g q6h, 0.5 g q8h, 0.5 g q12h, 1 g q6h, 1 g q8h, and 1 g q12h) on the probability of target attainment.

FINDINGS

Thirty patients were included in the population model analysis. Imipenem concentration data were best described by a 3-compartment model (central, peripheral, and dialysis compartments). The clearance of the dialysis compartment (CL_d) was used to characterize drug elimination from the dialyzer. Creatinine clearance (CrCl) was the covariate that influenced the central clearance (CLc), and the effects of dialysate flow (Qd) was significant for CLd. Model validation revealed that the final model had qualified stability and acceptable predictive properties. A pharmacokinetic and pharmacodynamic analysis was conducted by Monte Carlo simulation, and patients were categorized into 12 subgroups based on different CrCl values (<30, 31-60, 61-90, and >90 mL/min) and Qd values (300, 500, and 1000 mL/h). Under the same MIC value and administration regimen, probability of target attainment values decreased with an increase of CrCl and Qd.

IMPLICATIONS

CrCl and Qd had significant effects on CL_c and CL_d, respectively. The proposed final model may be used to guide practitioners in imipenem dosing in this specific patient population.

Pharmacokinetic and Pharmacodynamic Characteristics of Vancomycin and Meropenem in Critically Ill Patients Receiving Sustained Low-efficiency Dialysis

PURPOSE

Antibiotic dosing is challenge in critically ill patients undergoing renal replacement therapy. Our aim was to evaluate the pharmacokinetic and pharmacodynamic (PK/PD) characteristics of meropenem and vancomycin in patients undergoing SLED.

METHODS

Consecutive ICU patients undergoing SLED and receiving meropenem and/or vancomycin were prospectively evaluated. Serial blood samples were collected before, during, and at the end of SLED sessions. Antimicrobial concentrations were determined using a validated HPLC method. Noncompartmental PK analysis was performed. AUC was determined for vancomycin. For meropenem, time above MIC was calculated.

FINDINGS

A total of 24 patients receiving vancomycin and 21 receiving meropenem were included; 170 plasma samples were obtained. Median serum vancomycin and meropenem concentrations before SLED were 24.5 and 28.0 μg/mL, respectively; after SLED, 14 and 6 μg/mL. Mean removal was 42% with vancomycin and 78% with meropenem. With vancomycin, 19 (83%), 16 (70%), and 15 (65%) patients would have achieved the target (AUC_0-24 >400) considering MICs of 1, 2, and 4 mg/L, respectively. With meropenem, 17 (85%), 14 (70%), and 10 (50%) patients would have achieved the target (100% of time above MIC) if infected with isolates with MICs of 1, 4, and 8 mg/L, respectively.

IMPLICATIONS

SLED clearances of meropenem and vancomycin were 3-fold higher than the clearance described by continuous methods. Despite this finding, overall high PK/PD target attainments were obtained, except for at higher MICs. We suggest a maintenance dose of 1 g TID or BID of meropenem. With vancomycin, a more individualized approach using therapeutic drug monitoring should be used, as commercial assays are available.

Monitoring of cefepime in urine by micellar electrokinetic capillary chromatography with ultraviolet detection and liquid chromatography coupled to mass spectrometry

Cefepime monitoring in urine by micellar electrokinetic capillary chromatography with UV detection and liquid chromatography coupled to mass spectrometry via electrospray ionization is described. For micellar electrokinetic capillary chromatography, sample preparation comprised urine dilution and dodecyl-sulfate protein precipitation at pH 4.5, whereas diluted urines were analyzed in the other assay. Both approaches provided suitable conditions for cefepime analysis in urines of healthy volunteers that were spiked with cefepime. Cefepime monitoring by micellar electrokinetic capillary chromatography in samples from patients taking multiple drugs were prone to interferences, whereas liquid chromatography coupled to mass spectrometry provided clean chromatograms and thus selective detection of cefepime in all samples. The latter assay was used to measure urinary cefepime in a prospective pilot study and to assess cefepime stability in urines at 25, 4, -20 and -70°C. The data suggest that urinary cefepime is stable for at least 72 h at all tested temperatures.

Quantification of Cefepime, Meropenem, Piperacillin, and Tazobactam in Human Plasma Using a Sensitive and Robust Liquid Chromatography-Tandem Mass Spectrometry Method, Part 1: Assay Development and Validation

The highly variable pharmacokinetics of β-lactam antibiotics and β-lactamase inhibitors poses a significant challenge to clinicians in ensuring appropriate antibiotic doses in critically ill patients. Therefore, routine monitoring of plasma concentrations is important for individualization of antimicrobial therapy. Accordingly, a simple and robust analytical method for the simultaneous measurement of multiple β-lactam antibiotics and β-lactamase inhibitors is highly desirable to ensure quick decisions on dose adjustments. In this study, a sensitive, simple, and robust method for the simultaneous quantification of cefepime, meropenem, piperacillin, and tazobactam in human plasma was developed and rigorously validated according to FDA guidance. Sample extraction was accomplished by simple protein precipitation. Chromatographic separation of analytes was achieved using stepwise gradient elution. Analytes were monitored using tandem mass spectrometry (MS/MS) with a turbo ion spray source in positive multiple-reaction-monitoring mode. The calibration curve ranged from 0.5 to 150 μg/ml for cefepime, 0.1 to 150 μg/ml for meropenem and piperacillin, and 0.25 to 150 μg/ml for tazobactam. Inter- and intraday precision and accuracy, sensitivity, selectivity, dilution integrity, matrix effect, extraction recovery, and hemolysis effect were investigated for all four analytes, and the results met the acceptance criteria. Compared to other reported methods, our method is more robust because of the combination of the following features: (i) a simple sample extraction procedure, (ii) a short sample run time, (iii) a wide dynamic range, and (iv) the small plasma sample volume needed. Since our method already covers β-lactams and a β-lactamase inhibitor with highly heterogeneous physicochemical properties, further antibiotic candidates may easily be incorporated into this multianalyte method.

Vancomycin Determination by Disrupting Electron-Transfer in a Fluorescence Turn-On Squaraine-Anthraquinone Triad

A highly sensitive and selective probe for Vancomycin (Van) in aqueous and serum samples is developed in this study. The probe is based on a triad consisting of a near-infrared squaraine dye (Seta-640) conjugated to two anthraquinone molecules via Lys-d-Ala-d-Ala peptides. In the absence of Van, the close proximity and efficient electron-transfer from the excited Seta-640 dye to anthraquinone result in significant fluorescence quenching of the dye ("off"-state). When Van is added, the antibiotic molecules bind with high affinity to the -d-Ala-d-Ala ligands in a 2:1 stoichiometry (Van:triad), resulting in fluorescence recovery that is as high as 30 times ("on"-state). Even though bound Van enhances the fluorescence by reducing the rate of (intrinsic) polarity-induced nonradiative decay process, this effect plays only a minor role. Instead, the main reason behind the observed fluorescence recovery after drug binding is the effective inhibition of electron-transfer; plausibly arising from a steric-induced lengthening of the spatial separation between electron donor and acceptor. The probe has detection limits of 7.0 and 96.9 nM in buffer and human serum, respectively, operates in the clinically relevant range, is insensitive to Van crystalline degradation product (CDP-1), and is easy to operate by using a commonly available fluorescence spectrometer.

Simultaneous determination of zidebactam and cefepime in dog plasma by LC-MS/MS and its application to pre-clinical pharmacokinetic study

A precise and accurate liquid chromatography-tandem mass spectrometric (LC-MS/MS) bioanalytical method has been developed and validated for the simultaneous quantification of zidebactam (ZID) and cefepime (FEP) in dog plasma. Ceftazidime was used as an internal standard. Protein precipitation method was used as sample preparation approach. The calibration curve obtained was linear (r ≥ 0.99) over the concentration range 0.156-80 μg/mL for ZID and 0.312-160 μg/mL for FEP. The method was validated as per US Food and Drug Administration guidelines and the results met the acceptance criteria. A run time of 3.5 min for each sample made it possible to analyze the maximum number of samples per day. The proposed method was successfully applied for pharmacokinetic study in beagle dogs.

Determination of Vancomycin in Human Serum by Cyclodextrin-Micellar Electrokinetic Capillary Chromatography (CD-MEKC) and Application for PDAP Patients

A simple and sensitive cyclodextrin-micellar electrokinetic capillary chromatography (CD-MEKC) method with UV detection was developed and validated for the determination of vancomycin (VCM) in serum. The separation was achieved in 14 min at 25 °C with a fused-silica capillary column of 40.2 cm × 50 mm i.d. (effective length 30.2 cm) and a run buffer containing 25 mM borate buffer with 50 mM sodium dodecylsulfonate (SDS) (pH 9.5) and 2% sulfobutyl-β-cyclodextrin (sulfobutyl-β-CD). Under optimal conditions for biological samples, good separations with high efficiency and short analysis time were achieved. Several parameters affecting the drug separation from biological matrices were studied, including buffer types, concentrations, and pHs. The methods were validated over the range of 0.9998-99.98 µg/mL. Calibration curves of VCM also showed good linearity (r² > 0.999). Intra- and interday precisions (relative standard deviation, RSD) were less than 5.80% and 7.38%, and lower limit of quantification (LLOQ) were lower than 1.0 μg/mL. The mean recoveries ranged between 84.03% and 91.69%. The method was successfully applied for monitoring VCM concentrations in serum of patients with peritoneal dialysis-associated peritonitis (PDAP). The assay should be applicable to pharmacokinetic studies and routine therapeutic drug monitoring of this drug in serum.

Monitoring of cefepime in human serum and plasma by micellar electrokinetic capillary chromatography: Improvement of sample preparation and validation by liquid chromatography coupled to mass spectrometry

Cefepime monitoring in deproteinized human serum and plasma by micellar electrokinetic capillary chromatography and liquid chromatography coupled to mass spectrometry in presence of other drugs is reported. For micellar electrokinetic capillary chromatography, sample preparation comprised dodecylsulfate protein precipitation at pH 4.5 using an increased buffer concentration compared to that of a previous assay and removal of hydrophobic compounds with dichloromethane. This provided robust conditions for cefepime analysis in the presence of sulfamethoxazole and thus enabled its determination in samples of patients that receive cotrimoxazole. The liquid chromatography assay is based upon use of a column with a pentafluorophenyl-propyl modified and multiendcapped stationary phase and the coupling to electrospray ionization with a single quadrupole detector. The performances of both assays with multilevel internal calibration were assessed with calibration and control samples and both assays were determined to be robust. Cefepime levels monitored by micellar electrokinetic capillary chromatography in samples from patients that were treated with cefepime only and with cefepime and cotrimoxazole were found to compare well with those obtained by liquid chromatography coupled to mass spectrometry. Cefepime drug levels determined by micellar electrokinetic capillary chromatography could thereby be validated.

High-throughput determination of vancomycin in human plasma by a cost-effective system of two-dimensional liquid chromatography

Therapeutic drug monitoring (TDM) is one of the most important services of clinical laboratories. Two main techniques are commonly used: the immunoassay and chromatography method. We have developed a cost-effective system of two-dimensional liquid chromatography with ultraviolet detection (2D-LC-UV) for high-throughput determination of vancomycin in human plasma that combines the automation and low start-up costs of the immunoassay with the high selectivity and sensitivity of the liquid chromatography coupled with mass spectrometric detection without incurring their disadvantages, achieving high cost-effectiveness. This 2D-LC system offers a large volume injection to provide sufficient sensitivity and uses simulated gradient peak compression technology to control peak broadening and to improve peak shape. A middle column was added to reduce the analysis cycle time and make it suitable for high-throughput routine clinical assays. The analysis cycle time was 4min and the peak width was 0.8min. Compared with other chromatographic methods that have been developed, the analysis cycle time and peak width for vancomycin was reduced significantly. The lower limit of quantification was 0.20μg/mL for vancomycin, which is the same as certain LC-MS/MS methods that have been recently developed and validated. The method is rapid, automated, and low-cost and has high selectivity and sensitivity for the quantification of vancomycin in human plasma, thus making it well-suited for use in hospital clinical laboratories.

Pharmacokinetics of Cefepime in Patients with Cancer and Febrile Neutropenia in the Setting of Hematologic Malignancies or Hematopoeitic Cell Transplantation

STUDY OBJECTIVE

To evaluate the steady-state pharmacokinetic parameters of standard cefepime dosing regimens in a hematologic malignancy and hematopoietic cell transplant patient population with febrile neutropenia.

DESIGN

Open-label, single-center, prospective pharmacokinetic study.

SETTING

National Cancer Institute-designated cancer center.

PATIENTS

Nine adults with hematologic malignancies or hematopoietic cell transplants who had febrile neutropenia and were admitted to a hematology-oncology service between January and July 2014.

INTERVENTION

Patients received empirical cefepime 2 g every 8 hours, administered as a 30-minute intravenous infusion, for febrile neutropenia.

MEASUREMENTS AND MAIN RESULTS

Steady-state cefepime serum concentrations were measured after at least 2 days of continuous therapy. Venous blood samples were intensively sampled between 0 and 8 hours after the start of the 30-minute infusion at steady state. Seven of the nine patients had a hematologic malignancy diagnosis of acute leukemia, lymphoma, or myeloma, and two patients had a germ cell tumor diagnosis. Noncompartmental analysis revealed mean ± SD parameters as follows at steady state: area under the plasma concentration-time curve from 0-8 hours 222.9 ± 72.9 mg hour/L, maximum concentration 120.9 ± 21.8 mg/L, clearance 9.7 ± 3.7 L/hour, apparent volume of distribution 19.2 ± 4.65 L, and elimination half-life 1.4 ± 0.3 hours. A one-compartment pharmacokinetic model identified a mean ± SD volume of distribution of 20.9 ± 1.3 L and an elimination rate constant of 0.39 ± 0.03 hour(-1) . The mean estimated percentage of time that drug concentration remains above the pathogen minimum inhibitory concentration (fT>MIC) in serum was 55%, 77%, and 99% at MICs of 16, 8, and 4 mg/L, respectively.

CONCLUSION

Patients with hematologic malignancies or hematopoietic cell transplants who had febrile neutropenia demonstrated homogeneous calculated cefepime volumes and clearances. The population parameters presented in this study may aid in the calculation of patient-specific fT>MIC for similar patients.

Therapeutic drug monitoring of cefepime with micellar electrokinetic capillary chromatography: Assay improvement, quality assurance, and impact on patient drug levels

The improvement and performance of a micellar electrokinetic capillary chromatography assay for cefepime in human serum and plasma with a 50 μm id fused-silica capillary elongated from 40 to 60 cm is reported. Sample preparation with dodecylsulfate protein precipitation at pH 4.5, the pH 9.1 separation medium, and the applied voltage were as reported previously [16]. The change resulted in a significant lower current, higher resolution, and increased detection time intervals. The performance of the assay with multilevel internal calibration was assessed with calibration and control samples. Quality assurance data of a 2-year period assessed under the new conditions demonstrated the robustness of the assay. In serum samples of patients who received both cefepime and sulfamethoxazole, cefepime could not be detected due to the inseparability of the two compounds. The presence of an interference can be recognized by an increased peak width (width > 0.2 min), the appearance of a shoulder or an unresolved double peak. The patient data gathered during a 3-year period reveal that introduction of therapeutic drug monitoring led to a 50% reduction of the median drug level. The data suggest that therapeutic drug monitoring can help to minimize the risk of major adverse reactions and to increase drug safety on an individual basis.

Clinical Validation of Therapeutic Drug Monitoring of Imipenem in Spent Effluent in Critically Ill Patients Receiving Continuous Renal Replacement Therapy: A Pilot Study

Objectives

The primary objective of this pilot study was to investigate whether the therapeutic drug monitoring of imipenem could be performed with spent effluent instead of blood sampling collected from critically ill patients under continuous renal replacement therapy.

Methods

A prospective open-label study was conducted in a real clinical setting. Both blood and effluent samples were collected pairwise before imipenem administration and 0.5, 1, 1.5, 2, 3, 4, 6, and 8 h after imipenem administration. Plasma and effluent imipenem concentrations were determined by reversed-phase high-performance liquid chromatography with ultraviolet detection. Pharmacokinetic and pharmacodynamic parameters of blood and effluent samples were calculated.

Results

Eighty-three paired plasma and effluent samples were obtained from 10 patients. The Pearson correlation coefficient of the imipenem concentrations in plasma and effluent was 0.950 (P<0.0001). The average plasma-to-effluent imipenem concentration ratio was 1.044 (95% confidence interval, 0.975 to 1.114) with Bland-Altman analysis. No statistically significant difference was found in the pharmacokinetic and pharmacodynamic parameters tested in paired plasma and effluent samples with Wilcoxon test.

Conclusion

Spent effluent of continuous renal replacement therapy could be used for therapeutic drug monitoring of imipenem instead of blood sampling in critically ill patients.

Impact of the introduction of real-time therapeutic drug monitoring on empirical doses of carbapenems in critically ill burn patients

PURPOSE

Adequate empirical antibiotic dose selection for critically ill burn patients is difficult due to extreme variability in drug pharmacokinetics. Therapeutic drug monitoring (TDM) may aid antibiotic prescription and implementation of initial empirical antimicrobial dosage recommendations. This study evaluated how gradual TDM introduction altered empirical dosages of meropenem and imipenem/cilastatin in our burn ICU.

METHODS

Imipenem/cilastatin and meropenem use and daily empirical dosage at a five-bed burn ICU were analyzed retrospectively. Data for all burn admissions between 2001 and 2011 were extracted from the hospital's computerized information system. For each patient receiving a carbapenem, episodes of infection were reviewed and scored according to predefined criteria. Carbapenem trough serum levels were characterized. Prior to May 2007, TDM was available only by special request. Real-time carbapenem TDM was introduced in June 2007; it was initially available weekly and has been available 4 days a week since 2010.

RESULTS

Of 365 patients, 229 (63%) received antibiotics (109 received carbapenems). Of 23 TDM determinations for imipenem/cilastatin, none exceeded the predefined upper limit and 11 (47.8%) were insufficient; the number of TDM requests was correlated with daily dose (r=0.7). Similar numbers of inappropriate meropenem trough levels (30.4%) were below and above the upper limit. Real-time TDM introduction increased the empirical dose of imipenem/cilastatin, but not meropenem.

CONCLUSIONS

Real-time carbapenem TDM availability significantly altered the empirical daily dosage of imipenem/cilastatin at our burn ICU. Further studies are needed to evaluate the individual impact of TDM-based antibiotic adjustment on infection outcomes in these patients.

Development and validation of a new ultra-performance liquid chromatographic method for vancomycin assay in serum and its application to therapeutic drug monitoring

OBJECTIVE

The aim of this study was to develop and validate an ultra-performance liquid chromatographic (UPLC) method with photodiode array detector for the measurement of vancomycin in human serum samples for therapeutic drug monitoring or other applications.

METHODS

The method included the extraction of vancomycin in serum by deproteinization with acetonitrile. The analyses were carried out using an ACQUITY UPLC BEH C(18) column (2.1 × 50 mm, 1.7 μm) using acetonitrile and 0.005 M KH(2)PO(4) buffer (pH 2.5) as the mobile phase at a flow rate of 0.3 mL/min, with photodiode array detection at 230 nm. The method was validated for extraction recovery, inter- and intraday precision (relative standard deviation, RSD%), and accuracy and stability of vancomycin in serum. Both the established UPLC method and fluorescence polarization immunoassay (FPIA) were used to measure the prepared quality control (QC) samples (1.0, 7.0, 35.0, 75.0 mg/L) to validate the accuracy of UPLC. Furthermore, both methods were subsequently used to assay the vancomycin concentration in 172 clinical serum samples collected from patients receiving vancomycin in the hospitals localized in Shanghai (China) and 32 control samples from United Kingdom National External Quality Assessment Service (UK NEQAS).

RESULTS

The retention time of vancomycin was 2.6 minutes. The calibration curve for UPLC was linear over the range 1.0-100.0 mg/L (R(2) > 0.999). The method was fully validated in terms of recovery, selectivity, accuracy, precision, and various conditions. The absolute difference% and RSD% of the prepared QC samples assayed by UPLC were all better than the results by FPIA. A paired t test of the results of the prepared QC samples indicated that the results of all the QC samples had significant difference (P < 0.05), except for the 7.0 mg/L QC samples, which suggested that UPLC was more accurate for the samples containing low or high concentration of vancomycin. A correlation with the Deming model provided a good linear relation between the results of the 2 methods applied to 172 samples, with equation of UPLC = 0.99 × FPIA - 0.19 (R(2)= 0.923), and the agreement of the 2 methods was illustrated using Bland-Altman plot with a mean difference (UPLC - FPIA) of -0.428 mg/L and 95% confidence interval of -8.33 to 7.47 mg/L, respectively. A Student t test comparing results obtained by the UPLC method and group mean results of control samples from UK NEQAS were not significant (P = 0.057).

CONCLUSIONS

A short analysis time, small amount of serum needed, high specificity, and accuracy make the UPLC method developed in this study appropriate and practical for vancomycin therapeutic drug monitoring and could be applied to other nonserum applications or where requiring superior validation parameters such as for pharmacokinetic/pharmacodynamic studies.

A novel permanganate–morin–CdS quantum dots flow injection chemiluminescence system for sensitive determination of vancomycin

The intensity of emitted light from KMnO₄−morin−CdS QDs system is described as a novel chemiluminescence (CL) reaction. The CL intensity of this CL system was remarkably enhanced in the presence of vancomycin.

Electron transfer and fluorescence “turn-off” based CdTe quantum dots for vancomycin detection at nanogram level in aqueous serum media

Mode of interaction of GSH-CdTe QDs with vancomycin and the mechanism of the fluorescence “turn-off” process.

Ultrafast quantification of β-lactam antibiotics in human plasma using UPLC-MS/MS

There is an increasing interest in monitoring plasma concentrations of β-lactam antibiotics. The objective of this work was to develop and validate a fast ultra-performance liquid chromatographic method with tandem mass spectrometric detection (UPLC-MS/MS) for simultaneous quantification of amoxicillin, cefuroxime, ceftazidime, meropenem and piperacillin with minimal turn around time. Sample clean-up included protein precipitation with acetonitrile containing 5 deuterated internal standards, and subsequent dilution of the supernatant with water after centrifugation. Runtime was only 2.5 min. Chromatographic separation was performed on a Waters Acquity UPLC system using a BEH C18 column (1.7 μm, 100 mm × 2.1 mm) applying a binary gradient elution of water and methanol both containing 0.1% formic acid and 2 mmol/L ammonium acetate on a Water TQD instrument in MRM mode. All compounds were detected in electrospray positive ion mode and could be quantified between 1 and 100 mg/L for amoxicillin and cefuroxime, between 0.5 and 80 mg/L for meropenem and ceftazidime, and between 1 and 150 mg/L for piperacillin. The method was validated in terms of precision, accuracy, linearity, matrix effect and recovery and has been compared to a previously published UPLC-MS/MS method.

A degradation study of cefepime hydrochloride in solutions under various stress conditions by TLC-densitometry

A rapid, accurate and sensitive thin-layer chromatography (TLC) method with densitometric detection has been developed and validated for the determination of cefepime in pharmaceuticals. Chromatographic separation was achieved on a silica gel TLC F254 plates with a mobile phase consisting of ethanol-2-propanol-glacial acetic acid 99.5%-water (4:4:1:3, v/v). Densitometric detection was carried out at wavelength of 266 nm in reflectance/absorbance mode. The validation of the method was found to be satisfactory with high accuracy (from 99.24 to 101.37%) and precision (RSD from 0.06 to 0.36%). Additionally, the stability of cefepime in solution was investigated, including the effect of pH, temperature and incubation time. Favorable retention parameters (Rf , Rs, α) were obtained under the developed conditions, which guaranteed good separation of the studied components. The degradation process of cefepime hydrochloride was described by kinetic and thermodynamic parameters (k, t0.1 , t0.5 and Ea ). Moreover, the chemical properties of degradation products were characterized by the Rf values, absorption spectra, HPLC-MS/MS and TLC-densitometry analysis. As the method could effectively separate the active substance from its main degradation product (1-methylpyrrolidine), it can be employed as a method to indicate the stability of this drug.

CuO nanosheets-enhanced flow-injection chemiluminescence system for determination of vancomycin in water, pharmaceutical and human serum

A novel, rapid and sensitive CuO nanosheets (NSs) amplified flow-injection chemiluminescence (CL) system, luminol-H2O2-CuO nanosheets, was developed for determination of the vancomycin hydrochloride for the first time. It was found that vancomycin could efficiently inhibit the CL intensity of luminol-H2O2-CuO nanosheets system in alkaline medium. Under the optimum conditions, the inhibited CL intensity was linearly proportional to the concentration of vancomycin over the ranges of 0.5-18.0 and 18.0-40.0 mg L(-1), with a detection limit (3σ) of 0.1 mg L(-1). The precision was calculated by analyzing samples containing 5.0 mg L(-1) vancomycin (n=11) and the relative standard deviation (RSD) was 2.8%. Also, a high injection throughput of 120 sample h(-1) was obtained. The CuO nanosheets were synthesized by a sonochemical method. Also, X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses were employed to characterize the CuO nanosheets. The method was successfully employed to determine vancomycin hydrochloride in environmental water samples, pharmaceutical formulation and spiked human serum.

Simultaneous analysis of antibiotics in biological samples by ultra high performance liquid chromatography-tandem mass spectrometry

A rapid and reliable multiclass method was developed for the simultaneous analysis of 21 antibiotics (beta-lactams, aminoglycosides, penicillins, cephalosporins, carbapenems or quinolones) in urine, serum, cerebrospinal fluid (CSF) and bronchial aspirations by ultra-high performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS). Prior to chromatographic determination, the analytes were extracted from human biological fluids by simple sample treatments, which imply dilution, liquefaction, or protein precipitation. Several chromatographic conditions were optimized in order to obtain a fast separation (<6min for each chromatographic run). MS/MS conditions were evaluated in order to increase selectivity and sensitivity and all compounds were detected in electrospray (ESI) positive ion mode, except clavulanic acid and sulbactam, which were monitored in negative ion mode. The developed method was validated in terms of linearity, selectivity, limits of detection (LODs) and quantification (LOQs), trueness, repeatability and interday precision. The LOQs ranged from 0.01 to 1.00mg/L for urine, serum and CSF. In case of bronchial aspirations, the LOQs were between 0.02 and 0.67mg/kg. In all matrices the recovery results were in the range 70-120% and interday precision was lower than 25%. Finally, the optimized method was applied to the analysis of biological samples from 10 patients in the intensive care unit (ICU) of a hospital located in Almeria (Spain). Several antibiotics (e.g., amoxicillin, tobramycin, levofloxacin, or linezolid) were found in the studied samples, observing that the highest concentrations were obtained in urine samples.

Simultaneous and Direct Determination of Vancomycin and Cephalexin in Human Plasma by Using HPLC-DAD Coupled with Second-Order Calibration Algorithms

A simple, rapid, and sensitive method for the simultaneous determination of vancomycin and cephalexin in human plasma was developed by using HPLC-DAD with second-order calibration algorithms. Instead of a completely chromatographic separation, mathematical separation was performed by using two trilinear decomposition algorithms, that is, PARAFAC-alternative least squares (PARAFAC-ALSs) and self-weight-alternative-trilinear-decomposition- (SWATLD-) coupled high-performance liquid chromatography with DAD detection. The average recoveries attained from PARAFAC-ALS and SWATLD with the factor number of 4 (N = 4) were 101 ± 5% and 102 ± 4% for vancomycin, and 96 ± 3% and 97 ± 3% for cephalexininde in real human samples, respectively. The statistical comparison between PARAFAC-ALS and SWATLD is demonstrated to be similar. The results indicated that the combination of HPLC-DAD detection with second-order calibration algorithms is a powerful tool to quantify the analytes of interest from overlapped chromatographic profiles for complex analysis of drugs in plasma.

A liquid chromatography assay for a quantification of doripenem, ertapenem, imipenem, meropenem concentrations in human plasma: application to a clinical pharmacokinetic study

A simple chromatographic assay based on ultra high performance liquid chromatography with ultraviolet detection at 295 nm is proposed to determinate simultaneously human plasma concentrations of imipenem, doripenem, meropenem and ertapenem. After deproteinization by acetonitrile, carbapenems are separated on a PentaFluoroPhenyl column with a binary gradient elution. This method is specific, accurate, precise (the intra-day and inter-day imprecision and inaccuracy are lower than 15%), sensitive (the limit of quantitation is equal to 0.50 mg/L for imipenem, doripenem, ertapenem, meropenem) and not time consuming (run time=7 min). An application of this method to measure ertapenem plasma concentrations in burn patients is presented.

Determination of vancomycin in human plasma using high-performance liquid chromatography with fluorescence detection

A high-performance liquid chromatographic (HPLC) method with fluorescence detection for the quantification of vancomycin in human plasma was developed and validated. The method includes an extraction of vancomycin by deproteinization with acetonitrile. The analyses were carried out at 258 nm as the emission wavelength while exciting at 225 nm on a reversed-phase column (30 cm x 4 mm i.d. x 10 microm Waters Associates microBondapak C18) using a mobile phase composed of methanol and phosphate buffer at pH 6.3. Vancomycin was quantitatively recovered from human plasma samples (>96%) with high values of precision. The separation was completed within 27 min. The calibration curve was linear over the range from 5 to 1,000 ng/mL with the detection and quantification limits of 2 ng/mL and 5 ng/mL, respectively. This method is suitable for the routine assay of plasma samples.