Determination of Cefalothin and Cefazolin in Human Plasma, Urine and Peritoneal Dialysate by UHPLC-MS/MS: application to a pilot pharmacokinetic study in humans

Effect of Inadequate Treatment in Adult Patients with Community-Acquired Acute Pyelonephritis Due to Enterobacterales Under Empirical Management with Cefazolin

Background/Objectives: First-generation cephalosporins are used in some countries, primarily in Latin America and other low-resource regions, as a first-line or alternative empirical treatment for patients with acute pyelonephritis (AP). This study aimed to evaluate the impact of inappropriate empirical therapy with cefazolin on the clinical outcomes of adult patients with community-acquired AP caused by resistant Enterobacterales, requiring hospitalization in two tertiary hospitals in Bogotá. Methods: This retrospective cohort study included hospitalized patients with community-acquired AP caused by Enterobacterales who received initial treatment with cefazolin at two tertiary-level institutions in Colombia (January 2013-2020). Inappropriate treatment was defined as a resistant isolate to cefazolin in the urine culture. Outcomes assessed included hospital stay, hospital mortality, and recurrence. Results: A total of 1031 patients were admitted, among whom 218 (21.1%) received inappropriate treatment. The mean length of stay was 4.8 (5.1) days, 996 (96.6%) survived to discharge, and 113 (11.0%) were admitted for a recurrence of AP. Inappropriate treatment had no impact on hospital stay (RRA 0.98, 95% CI 0.84-1.15) or hospital mortality (OR 1.02, 95% CI 0.47-2.19), although it was associated with a greater risk of admission because of recurrence (OR 3.7, 95% CI 2.4-5.8). Conclusions: We found that inadequate empirical treatment with cefazolin in adult patients with community-acquired acute pyelonephritis does not appear to change the length of hospital stay or in-hospital mortality in patients but is associated with an increased risk of readmission due to recurrence; this might favor the use of empirical narrow-spectrum antibiotics but with strategies that allow monitoring or early detection of microbiological non-eradication to prevent recurrence.

Safety, tolerability and pharmacokinetics of subcutaneous cefazolin as an alternative to intravenous administration

BACKGROUND

Subcutaneous (SC) administration of antibiotics is a practical alternative to IV administration. Cefazolin is widely used for skin and soft tissue infections and other complex infections by IV administration.

METHODS

In this prospective, cross-over self-controlled study, a single dose of SC cefazolin was administered to 15 stable inpatients established on IV cefazolin as part of their management plan. The equivalent dose of cefazolin was diluted in 50 mL of normal saline via gravity feed over 30 min. Venous blood samples were collected at baseline and 0.5, 1, 2, 4 and 8 h following both the SC and IV doses. Antibiotic concentrations were measured using UPLC-MS/MS. Pharmacokinetic data were analysed using a non-linear mixed-effects modelling approach. Pain scores and infusion site reactions (oedema/erythema) were evaluated.

RESULTS

SC cefazolin was well tolerated. The bioavailability of SC administration was 74.8% (95% CI 66.7%-81.7%). Slower absorption from SC tissue was associated with a BMI of ≥30. Lower peak, and higher trough concentrations were observed with SC administration. Although lower bioavailability was observed with SC administration, the PTA for unbound drug concentrations greater than the MIC for more than 90% of the time between doses was higher for SC compared with IV administration at MICs between 0.25 and 4 mg/L. Simulated SC doses of 3 g twice daily had similar PTA to standard IV dosing of 2 g three times daily. A simulated 6 g continuous 24 h infusion of SC cefazolin had a favourable pharmacokinetic profile.

CONCLUSION

SC cefazolin appears to be well tolerated, with an improved pharmacokinetic profile compared with IV administration. Either 3 g twice daily, or 6 g as a 24 h SC infusion could be considered for future evaluation.

Recent Advances in Bioanalysis of Cephalosporins Toward Green Sample Preparation

This review highlights recent advances in the bioanalysis of cephalosporins using liquid chromatographic methods, focusing on green sample preparation (GSP) techniques. Cephalosporins, a class of β-lactam antibiotics, are critical in combating bacterial infections but present challenges related to drug resistance and toxicity. This article evaluates various sample preparation methods, including solid-phase extraction, solid-phase microextraction, and protein precipitation, which have been employed in the extraction and quantification of cephalosporins from biological matrices. Special attention is given to the optimization of critical parameters, such as pH, extraction solvents, and purification techniques to maximize analytes' recovery and sensitivity. Emerging trends in GSP, such as the use of molecularly imprinted polymers and miniaturized processing devices, are also discussed. The review underscores the growing importance of integrating environmentally friendly approaches in cephalosporin bioanalysis, paving the way for future innovations in bioanalytical research.

Safety, tolerability and pharmacokinetics of subcutaneous meropenem as an alternative to intravenous administration

BACKGROUND

Subcutaneous delivery of antibiotics is a practical alternative to IV administration. Meropenem is commonly used to treat infections caused by resistant Gram-negative organisms.

METHODS

This was a prospective, crossover self-controlled study in 11 stable inpatients established on meropenem. Participants received a single dose of subcutaneous meropenem, in 50 mL normal saline via gravity feed. Venous blood sampling was performed at baseline, 0.5, 1, 2, 4 and 8 h following the subcutaneous and IV doses. Antibiotic concentrations were measured using UPLC-MS/MS. Pharmacokinetic data were analysed using a non-linear mixed-effects modelling approach. Pain scores and infusion site reactions (oedema/erythema) were assessed.

RESULTS

Subcutaneous meropenem was well tolerated. The bioavailability of subcutaneous administration was 81.5% (95% CI 71.6%-93.2%). Increasing BMI was associated with slower absorption from subcutaneous tissue. Compared with IV, subcutaneous administration resulted in lower peak and higher trough concentrations. Despite the lower bioavailability observed, the PTA for free drug concentrations greater than the MIC for more than 40% of the time between doses was higher for subcutaneous than IV administration at MIC values between 0.03 and 8 mg/L. Simulated subcutaneous doses of 1.5 g twice daily, or 3 g continuous 24 h infusion had improved PTA relative to standard IV dosing of 1 g three times daily.

CONCLUSIONS

Subcutaneous meropenem appears to be well tolerated and has a favourable pharmacokinetic profile. Either 1.5 g twice daily or 3 g as a 24 h subcutaneous infusion could be considered for future evaluation.

Can capillary microsampling facilitate a clinical pharmacokinetics study of cefazolin in critically ill children?

Aim: Pharmacokinetic studies in children are limited, in part due to challenges in blood sampling. We compare the use of capillary microsampling and conventional sampling techniques in pediatric patients to show results that can be used in the pharmacokinetic analysis of Cefazolin.Patients & Methods: Paired blood samples (n = 48) were collected from 12 patients (median age/weight 49 months/18 kg).Results: The United States Federal Drug Administration incurred sample reanalysis acceptance criteria was used and identified 79% of paired samples achieved a difference of less than 20% in magnitude with a capillary microsampling bias of -10% (SD 20%). With exclusion of PK outliers, this rose to 88%.Conclusion: Capillary microsampling is reliable, meets acceptance criteria and can be used in pharmacokinetic studies.ACTRN: 12618001469202.

Peri-operative pharmacokinetics of cefazolin prophylaxis during valve replacement surgery

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Quantification of sixteen cephalosporins in the aquatic environment by liquid chromatography-tandem mass spectrometry

Antimicrobial agents are essential to protect human and animal health. During the COVID-19 pandemic, antimicrobials such as cephalosporins were widely used as prophylactics and to prevent bacterial co-infection. Undoubtedly, the prevalence of antibiotics in the aquatic environment will ultimately affect the degree of resistance against these bacteria in animals and the environmental systems. In order to monitor sixteen cephalosporins in the aquatic environment, we developed a new LC-MS/MS method that functioned simultaneously under positive and negative ESI switching modes. The chromatographic separation has been implemented using a pentafluorophenyl propyl column kept at 40°C. The limits of detection and quantitation for the studied cephalosporins ranged from (8 × 10^-4 ) to (7.11 × 10^-2 ) ng/mL and from (2.61 × 10^-3 ) to (2.37 × 10^-1 ) ng/mL, respectively. The percent extraction efficiency (apparent recovery) and relative standard deviations for the analyzed cephalosporins ranged from 61.69 to 167.67% and 2.45 to 13.48%, respectively. The overall findings showed that the effluent from the wastewater treatment plants that receive wastewater from pharmaceutical factories had a higher detected amount of cephalosporins than that of domestic sewage. Moreover, seven cephalosporins, including cefuroxime, ceftazidime, cefradine, cefprozil, cefixime, cefalexin, and cefadroxil (0.68-105.45 ng/L) were determined in the aquatic environment. This article is protected by copyright. All rights reserved.

Simple determination of urine cefazolin concentration in pediatric patients with urinary tract infections using high-performance liquid chromatography

Recently, global health concerns regarding increasing multidrug resistance have arisen. This study aimed to develop a simple, inexpensive, and rapid high-performance liquid chromatography-ultraviolet (HPLC-UV) method for determining urinary concentrations of a 1st generation cephem antibiotic in pediatric patients with urinary tract infections (UTIs). HPLC-UV was used to analyze urinary cefazolin concentrations at a detection wavelength of 254 nm. The assay used contained 10-fold diluted urine with an internal standard (cephapirin). The standard calibration curve for cefazolin was linear in the concentration range of 31.25-500 μg/mL (r² >0.999). The retention times of cefazolin and the internal standard were 4.2 and 4.9 min, respectively. The within-day and between-day coefficients of variation were at these concentrations ranged 1.2-15.2 and 5.5-19.2 %, respectively. The urinary cefazolin concentration of a pediatric patient with a UTI was 1,476.6 μg/mL, which was over 700-fold higher than the minimum inhibitory concentration (MIC) of cefazolin (≤ 2 μg/mL). The developed method is applicable to the confirmation of appropriate use for UTIs treatment as a therapeutic drug monitoring of cefazolin. Therefore, the findings of this study may contribute to the appropriate use of antibiotics to prevent antimicrobial resistance (AMR) in pediatric patients with UTIs.

Plasma and Interstitial Fluid Pharmacokinetics of Prophylactic Cefazolin in Elective Bariatric Surgery Patients

Guidelines for surgical prophylactic dosing of cefazolin in bariatric surgery vary in terms of recommended dose. This study aimed to describe the plasma and interstitial fluid (ISF) cefazolin pharmacokinetics in patients undergoing bariatric surgery and to determine an optimum dosing regimen. Abdominal subcutaneous ISF concentrations (measured using microdialysis) and plasma samples were collected at regular time points after administration of cefazolin 2 g intravenously. Total and unbound cefazolin concentrations were assayed and then modeled using Pmetrics. Monte Carlo dosing simulations (n = 5,000) were used to define cefazolin dosing regimens able to achieve a fractional target attainment (FTA) of >95% in the ISF suitable for the MIC for Staphylococcus aureus in isolates of ≤2 mg · L-1 and for a surgical duration of 4 h. Fourteen patients were included, with a mean (standard deviation [SD]) bodyweight of 148 (35) kg and body mass index (BMI) of 48 kg · m-2. Cefazolin protein binding ranged from 14 to 36% with variable penetration into ISF of 58% ± 56%. Cefazolin was best described as a four-compartment model including nonlinear protein binding. The mean central volume of distribution in the final model was 18.2 (SD 3.31) L, and the mean clearance was 32.4 (SD 20.2) L · h-1. A standard 2-g dose achieved an FTA of >95% for all patients with BMIs ranging from 36 to 69 kg · m-2. A 2-g prophylactic cefazolin dose achieves appropriate unbound plasma and ISF concentrations in obese and morbidly obese bariatric surgery patients.

An Overview of the Protein Binding of Cephalosporins in Human Body Fluids: A Systematic Review

Introduction: Protein binding can diminish the pharmacological effect of beta-lactam antibiotics. Only the free fraction has an antibacterial effect. The aim of this systematic literature review was to give an overview of the current knowledge of protein binding of cephalosporins in human body fluids as well as to describe patient characteristics influencing the level of protein binding. Method: A systematic literature search was performed in Embase, Medline ALL, Web of Science Core Collection and the Cochrane Central Register of Controlled Trials with the following search terms: "protein binding," "beta-lactam antibiotic," and "body fluid." Only studies were included where protein binding was measured in humans in vivo. Results: The majority of studies reporting protein binding were performed in serum or plasma. Other fluids included pericardial fluid, blister fluid, bronchial secretion, pleural exudate, wound exudate, cerebrospinal fluid, dialysate, and peritoneal fluid. Protein binding differs between diverse cephalosporins and between different patient categories. For cefazolin, ceftriaxone, cefpiramide, and cefonicid a non-linear pattern in protein binding in serum or plasma was described. Several patient characteristics were associated with low serum albumin concentrations and were found to have lower protein binding compared to healthy volunteers. This was for critically ill patients, dialysis patients, and patients undergoing cardiopulmonary bypass during surgery. While mean/median percentages of protein binding are lower in these patient groups, individual values may vary considerably. Age is not likely to influence protein binding by itself, however limited data suggest that lower protein binding in newborns. Obesity was not correlated with altered protein binding. Discussion/Conclusion: Conclusions on protein binding in other body fluids than blood cannot be drawn due to the scarcity of data. In serum and plasma, there is a large variability in protein binding per cephalosporin and between different categories of patients. Several characteristics were identified which lead to a lower protein binding. The finding that some of the cephalosporins display a non-linear pattern of protein binding makes it even more difficult to predict the unbound concentrations in individual patients. Taken all these factors, it is recommended to measure unbound concentrations to optimize antibiotic exposure in individual patients. Systematic Review Registration: PROSPERO, identifier (CRD42021252776).

A validated LC-MS/MS method for the quantitation of cefazolin in human adipose tissue: Application of EMR-Lipid sorbent as an efficient sample clean-up before mass spectrometric analyses

A novel, simple, rapid, and sensitive high-performance liquid chromatography-tandem mass spectrometry method was developed to determine cefazolin concentrations in human adipose tissue. Sample preparation was performed by protein precipitation followed by using Captiva EMR-Lipid plates. The mobile phase consisted of 5 mM ammonium formate and 0.1% formic acid in water and 0.1% formic acid in ACN, and was pumped through a Synergi Fusion-RP column with a gradient elution program at a flow rate of 0.3 mL/min. The mass spectrometer was operated in a positive ion mode. Cloxacillin was used as an internal standard due to the observed cross-signal contribution between cefazolin and ¹³C₂,¹⁵N-cefazolin. The method was validated according to the FDA and EMA guidelines and passed all the acceptance criteria. The calibration range was 0.05-50 µg/mL in adipose tissue homogenate (0.15-150 µg/g in adipose tissue), precision CV < 4.5%, accuracy within 93.1-100.4%. The carry-over was negligible, recovery of the method was high, and no significant matrix effect was present. Rat subcutaneous adipose tissue was demonstrated to be a suitable surrogate matrix for human adipose tissue. The validated method was successfully applied in a pilot pharmacokinetic study and will further be used in a large cohort of non-obese and obese patients dosed prophylactically with cefazolin before surgeries.

In vitro effect of synovial fluid from patients undergoing arthroplasty surgery on MRSA biofilm formation

BACKGROUND

Bacterial biofilm is a key component in the pathogenesis of prosthetic joint infection (PJI). Synovial fluid has been shown to have inhibitory activity against planktonic bacteria. However, the contribution of synovial fluid in prevention of Staphylococcus aureus (including MRSA) planktonic and biofilm forms is unknown.

OBJECTIVES

To test the antibacterial and antibiofilm activities of synovial fluid, including that containing cefazolin, against MSSA and MRSA.

MATERIALS AND METHODS

We determined the antiplanktonic and antibiofilm activities of synovial fluid collected from patients given preoperative cefazolin while undergoing elective arthroplasty surgery. MICs of cefazolin were determined for planktonic and biofilm cultures of biofilm-forming strains of MSSA and MRSA.

RESULTS

Synovial fluid inhibited planktonic and biofilm cultures of MSSA and MRSA. Cefazolin-containing synovial fluid had greater antibacterial and antibiofilm activities than the same cefazolin concentration in glucose LB (GLB) broth. MSSA and MRSA MICs of cefazolin suspended in synovial fluid were 0.7 mg/L. The MICs of cefazolin diluted in GLB broth were higher, measuring 1.4 mg/L for MSSA and 23 mg/L for MRSA.

CONCLUSIONS

Synovial fluid containing cefazolin inhibited biofilm- and planktonic-state MRSA cultures. This may explain the apparent effect of cefazolin in the prevention of MRSA PJI.

Development and validation of a simple and sensitive LC-MS/MS method for the quantification of cefazolin in human plasma and its application to a clinical pharmacokinetic study

Cefazolin is widely used during surgery to prevent surgical site infections (SSIs). Although cefazolin redosing is often needed due to its short half-life, the appropriate redosing schedule remains controversial and there is limited information on cefazolin disposition following repeated doses during surgery. In parallel with an ongoing cefazolin redosing clinical study, we have developed and fully validated a simple and robust liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the quantification of cefazolin in human plasma. A simple protein precipitation was used for sample preparation. MS/MS analysis was performed using multiple reaction monitoring (MRM) under a positive ionization mode. The lower limit of quantification (LLOQ) for cefazolin was evaluated at 0.25 µg/mL and a linearity ranging from 0.25 to 300 µg/mL. Accuracy was ≤ 114.3% for quality controls and ≤ 118.2% for LLOQ; intra-day and inter-day precision ranging from 1.9% to 14.2% for all quality controls and LLOQ. Matrix effect, extraction recovery, stability testing, dilution integrity, hemolysis effects and whole blood stability have all been investigated. A total of 17 parameters were validated and passed their validation criteria. The method was applied in the quantification of cefazolin in clinical plasma samples and was able to successfully determine the concentrations in patients undergoing various surgeries. In comparison with other prior published methods, our method has a simple sample preparation combined with a short analysis run time, a wide dynamic range and low limit of quantification, and is a fully validated assay that abides by FDA guidance.

CE-DAD-MS/MS in the simultaneous determination and identification of selected antibiotic drugs and their metabolites in human urine samples

In this study, a new analytical method was developed and validated for the simultaneous analysis of antibiotic drugs (amoxicillin, cefotaxime, ciprofloxacin, clindamycin, linezolid, metronidazole) and their metabolites (amoxycilloic acid, amoxicillin diketopiperazine, 3-desacetyl cefotaxime lactone, clindamycin sulfoxide, ciprofloxacin piperazinyl-N4-sulfate, linezolid N-oxide, metronidazole-OH) in human urine. Capillary electrophoresis (CE) along with the tandem mass spectrometry (MS/MS) was used to determine and identify all analytes. Appropriate conditions for MS/MS measurements along with the use of the central composite design were optimized. The effects of different analytical conditions (the composition, the concentration, and the pH value of the background electrolyte, the time and pressure of the injection, the capillary temperature and influence of the organic modifier) on the migration and separation of antibiotic drugs and metabolites were examined using the CE-DAD. The analytical procedure was linear for concentrations ranging from 20 to 1000 ng/mL, with determination coefficients higher than 0.99 for all the analytes. The validated analytical procedure was then applied to the measurement of antibiotic drugs and their metabolites in human urine samples.

Plasma concentrations of cefazolin in pediatric patients undergoing cardiac surgery

Background

The guideline for antibiotic prophylaxis in pediatric cardiac surgery is currently unavailable, and the effects of cardiopulmonary bypass (CPB) may result in low plasma cefazolin concentrations and subsequent postoperative surgical site infections (SSIs).

Aims

To demonstrate the calculated-unbound plasma concentrations of cefazolin during uncomplicated pediatric cardiac surgery.

Settings and Design

A prospective observational study that included 18 patients <seven years of age, undergoing elective cardiac surgery with CPB.

Materials and Methods

An intravenous infusion of cefazolin (25 mg.kg^-1) was administered to patients over 30 minutes within 1 hour before skin incision (first dose). Another 25 mg.kg^-1 infusion was administered to the CPB prime volume (second dose). Blood samples were obtained at eight time points: 15 minutes after the first dose (T1); before aortic cannulation (T2); immediately after CPB initiation (T3); 30 (T4), 60 (T5), and 120 (T6) minutes after CPB; 15 minutes after CPB discontinuation (T7), and at skin closure (T8). The total plasma cefazolin concentrations were measured using liquid chromatography tandem mass spectrometry.

Results

The unbound cefazolin concentrations were calculated assuming 80%-protein binding. The median cefazolin levels were 18.1 (range 4.3-27.0), 11.9 (2.8-24.1), 31.4 (18.3-66.1), 23.4 (13.7-35.9), 20.2 (15.4-24.9), 17.7 (14.8-18.0), 15.6 (9.8-26.2), and 13.3 (8.3-24.6) μg.mL^-1 from T1-T8, respectively. The cefazolin levels remained four times above the minimum inhibitory concentrations (MICs) for Methicillin-sensitive S. aureus (MSSA) and S. epidermidis in most patients, but they were inadequate for Enterobacter and E. coli.

Conclusion

This regimen produced adequate plasma cefazolin concentrations for common organisms that cause SSIs after cardiac surgery.

Cephalothin: Review of Characteristics, Properties and Status of Analytical Methods

BACKGROUND

Cephalothin (CET), a first generation cephalosporin, is the most efficient cephalosporin against resistant microorganisms. Many studies found in literature and pharmacopeias proposes analytical methods and, as most commonly, HPLC and microbiological assays.

OBJECTIVE

This paper shows a brief review of analytical method to quantify CET with a green analytical chemistry approach.

METHODS

The research data were collected from the literature and official compendia.

RESULTS

Most of the analytical methods to determine CET were performed by HPLC and agar diffusion in pharmaceuticals, blood, urine or water. Other analytical methods were found, as UV, Vis, iodometry, fluorimetry, IR/Raman, electrochemical among others, but, in less quantity. One important aspect is that these methods use organic and toxic solvents like methanol and acetonitrile, and only about 4% of the methods found uses water as solvent.

CONCLUSIONS

In this way, researches about analytical methods focused on green analytical chemistry for CET are of great importance and very relevant to optimize its analysis in pharmaceutical industries and to guarantee the quality of the product. More than just the development of new techniques it is possible to enhance of the ones that already exists applying the green analytical chemistry principles. In this way, it will be possible to reduce the environment impacts caused by these analytical procedures.

HIGHLIGHTS

This work shows a brief review of literature and pharmacopeias of analytical methods to quantify CET. Its quality control can be updated to meet the needs of current analytical chemistry and to fit into sustainable and eco-friendly analyzes.

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.

Copper nanoparticles for SERS-based determination of some cephalosporin antibiotics in spiked human urine

Copper nanoparticles (CuNPs) were prepared through a wet chemistry method to be used as substituents for noble-metal-based materials in the determination of cephalosporin antibiotics in urine using surface-enhanced Raman spectroscopy (SERS). The synthesis of the CuNPs was optimized to maximize the analytical signal, and microwave heating was used to increase the reaction rate and improve the homogeneity of the CuNPs. Ceftriaxone (CTR), cefazolin (CZL), and cefoperazone (CPR) were used as the analytes of interest. The determination tests were performed on artificially spiked samples of real human urine with concentrations corresponding to therapeutic drug monitoring (TDM) (50-500 μg mL^-1). Urine samples collected in the morning and during the day were used to account for deviations in the urine composition, and the universality of the proposed protocol was ensured by performing sample dilution as a pretreatment. The use of calibration plots in the form of Freundlich adsorption isotherms yielded linear calibration plots. All limits of detection were lower than the minimal concentrations required for TDM, equaling 7.5 (CTR), 8.8 (CZL), and 36 (CPR) μg mL^-1. Comparison of CuNPs with Ag and Au nanoparticles (AgNPs and AuNPs, respectively) confirmed that CuNPs offered a competitively high Raman enhancement efficiency (for excitation at 638 nm). Further, although the CuNPs demonstrated poorer temporal stability as compared with the AgNPs and AuNPs, the use of freshly prepared CuNPs resulted in satisfactory accuracy (recovery = 93-107%). Given the short analysis time (<20 min, including the time for the synthesis of the CuNPs and the SERS measurements using a portable Raman spectrometer), low sensitivity to the presence of the primary intrinsic urine components and satisfactory figures of merit of the proposed protocol for the determination of cephalosporin antibiotics in urine, it should be suitable for use in TDM.

Determination and Identification of Antibiotic Drugs and Bacterial Strains in Biological Samples

Antibiotics were initially natural substances. However, nowadays, they also include synthetic drugs, which show their activity against bacteria, killing or inhibiting their growth and division. Thanks to these properties, many antibiotics have quickly found practical application in the fight against infectious diseases such as tuberculosis, syphilis, gastrointestinal infections, pneumonia, bronchitis, meningitis and septicemia. Antibiotic resistance is currently a detrimental problem; therefore, in addition to the improvement of antibiotic therapy, attention should also be paid to active metabolites in the body, which may play an important role in exacerbating the existing problem. Taking into account the clinical, cognitive and diagnostic purposes of drug monitoring, it is important to select an appropriate analytical method that meets all the requirements. The detection and identification of the microorganism responsible for the infection is also an essential factor in the implementation of appropriate antibiotic therapy. In recent years, clinical microbiology laboratories have experienced revolutionary changes in the way microorganisms are identified. The MALDI-TOF MS technique may be interesting, especially in some areas where a quick analysis is required, as is the case with clinical microbiology. This method is not targeted, which means that no prior knowledge of the infectious agent is required, since identification is based on a database match.

Pharmacokinetics of Total and Unbound Cefazolin during Veno-Arterial Extracorporeal Membrane Oxygenation: A Case Report

Extra-corporeal membrane oxygenation (ECMO) therapy could affect effective drug concentrations via adsorption onto the oxygenator or associated circuit. We describe a case of a 25-year-old female who required a veno-arterial ECMO therapy for refractory cardiac arrest due to massive pulmonary embolism. She had mild renal dysfunction as a result of the cardiac arrest. A total of 2 g of intravenous cefazolin 8-hourly was administered. Pre- and post-oxygenator blood samples were collected at 0, 1, 4, and 8 h post antibiotic administration. Samples were analyzed for total and unbound cefazolin concentrations. Protein binding was ∼60%. Clearance was reduced due to impaired renal function. The pharmacokinetics of cefazolin appear to not be affected by ECMO therapy and dosing adjustment may not be required.

Comparative total and unbound pharmacokinetics of cefazolin administered by bolus versus continuous infusion in patients undergoing major surgery: a randomized controlled trial

Background.

Perioperative administration of cefazolin reduces the incidence of perioperative infections. Intraoperative re-dosing of cefazolin is commonly given between 2 and 5 h after the initial dose. This study was undertaken to determine whether intraoperative continuous infusions of cefazolin achieve better probability of target attainment (PTA) and fractional target attainment (FTA) than intermittent dosing.

Methods.

Patients undergoing major surgery received cefazolin 2 g before surgical incision. They were subsequently randomized to receive either an intermittent bolus (2 g every 4 h) or continuous infusion (500 mg h -1 ) of cefazolin until skin closure. Blood samples were analysed for total and unbound cefazolin concentrations using a validated chromatographic method. Population pharmacokinetic modelling was performed using Pmetrics ® software. Calculations of PTA and FTA were performed for common pathogens.

Results.

Ten patients were enrolled in each arm. A two-compartment linear model best described the time course of the total plasma cefazolin concentrations. The covariates that improved the model were body weight and creatinine clearance. Protein binding varied with time [mean (range) 69 (44-80)%] with a fixed 21% unbound value of cefazolin used for the simulations (120 min post-initial dosing). Mean ( sd ) central volume of distribution was 5.73 (2.42) litres, and total cefazolin clearance was 4.72 (1.1) litres h -1 . Continuous infusions of cefazolin consistently achieved better drug exposures and FTA for different weight and creatinine clearances, particularly for less susceptible pathogens.

Conclusions.

Our study demonstrates that intraoperative continuous infusions of cefazolin increase the achievement of target plasma concentrations, even with lower infusion doses. Renal function and body weight are important when considering the need for alternative dosing regimens.

Clinical trial registration.

NCT02058979.

Simultaneous quantification of fentanyl, sufentanil, cefazolin, doxapram and keto-doxapram in plasma using liquid chromatography-tandem mass spectrometry

A simple and specific UPLC–MS/MS method was developed and validated for simultaneous quantification of fentanyl, sufentanil, cefazolin, doxapram and its active metabolite keto‐doxapram. The internal standard was fentanyl‐d5 for all analytes. Chromatographic separation was achieved with a reversed‐phase Acquity UPLC HSS T3 column with a run‐time of only 5.0 min per injected sample. Gradient elution was performed with a mobile phase consisting of ammonium acetate or formic acid in Milli‐Q ultrapure water or in methanol with a total flow rate of 0.4 mL min⁻¹. A plasma volume of only 50 μL was required to achieve adequate accuracy and precision. Calibration curves of all five analytes were linear. All analytes were stable for at least 48 h in the autosampler. The method was validated according to US Food and Drug Administration guidelines. This method allows quantification of fentanyl, sufentanil, cefazolin, doxapram and keto‐doxapram, which is useful for research as well as therapeutic drug monitoring, if applicable. The strength of this method is the combination of a small sample volume, a short run‐time, a deuterated internal standard, an easy sample preparation method and the ability to simultaneously quantify all analytes in one run.

Fast and sensitive HPLC/UV method for cefazolin quantification in plasma and subcutaneous tissue microdialysate of humans and rodents applied to pharmacokinetic studies in obese individuals

Antimicrobial prophylactic dosing of morbidly obese patients may differ from normal weighted individuals owing to alterations in drug tissue distribution. Drug subcutaneous tissue distribution can be investigated by microdialysis patients and animals. The need for cefazolin prophylactic dose adjustment in obese patients remains under discussion. The paper describes the validation of an HPLC-UV method for cefazolin quantification in plasma and microdialysate samples from clinical and pre-clinical studies. A C₁₈ column with an isocratic mobile phase was used for drug separation, with detection at 272 nm. Total and unbound cefazolin lower limit of quantitation was 5 μg/mL in human plasma, 2 μg/mL in rat plasma, and 0.5 and 0.025 μg/mL in human and rat microdialysate samples, respectively. The maximum intra- and inter-day imprecisions were 10.7 and 8.1%, respectively. The inaccuracy was <9.7%. The limit of quantitation imprecision and inaccuracy were < 15%. Cefazolin stability in the experimental conditions was confirmed. Cefazolin plasma concentrations and subcutaneous tissue penetration were determined by microdialysis in morbidly obese patients (2 g i.v. bolus) and diet-induced obese rats (30 mg/kg i.v. bolus) using the method. This method has the main advantages of easy plasma clean-up and practicability and has proven to be useful in cefazolin clinical and pre-clinical pharmacokinetic investigations.

Pharmacokinetics of Intraperitoneal Cefalothin and Cefazolin in Patients Being Treated for Peritoneal Dialysis-Associated Peritonitis

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BACKGROUND

The standard treatment of peritoneal dialysis (PD)-associated peritonitis (PD-peritonitis) is intraperitoneal (IP) administration of antibiotics. Only limited data on the pharmacokinetics and appropriateness of contemporary dose recommendations of IP cefalothin and cefazolin exist. The aim of this study was to describe the pharmacokinetics of IP cefalothin and cefazolin in patients treated for PD-peritonitis. ♦

METHODS

As per international guidelines, IP cefalothin or cefazolin 15 mg/kg once daily was dosed with gentamicin in a 6-hour dwell to patients with PD-peritonitis during routine care. Serial plasma and PD effluent samples were collected over the first 24 hours of therapy. Antibiotic concentrations were quantified using a validated chromatographic method with pharmacokinetic analysis performed using a non-compartmental approach. ♦

RESULTS

Nineteen patients were included (cefalothin n = 8, cefazolin n = 11). The median bioavailability for both antibiotics exceeded 92%, but other pharmacokinetic parameters varied markedly between antibiotics. Both antibiotics achieved high PD effluent concentrations throughout the antibiotic dwell. Cefazolin had a smaller volume of distribution compared with cefalothin (14 vs 40 L, p = 0.003). The median trough total plasma antibiotic concentration for cefazolin and cefalothin during the dwell differed (plasma 56 vs 13 mg/L, p < 0.0001) despite a similar concentration in PD effluent (37 vs 38 mg/L, p = 0.58). Lower antibiotic concentrations were noted during PD dwells not containing antibiotic, particularly cefalothin, which was frequently undetectable in plasma and PD effluent. The median duration that the unbound antibiotic concentration was above the minimum inhibitory concentration (MIC) was approximately 13% (plasma) and 25% (IP) for cefalothin, and 100% (plasma and IP) for cefazolin, of the dosing interval. ♦

CONCLUSIONS

When IP cefalothin or cefazolin is allowed to dwell for 6 hours, sufficient PD effluent concentrations are present for common pathogens during this time. However, with once-daily IP dosing, in contrast to cefazolin, there is a risk of subtherapeutic plasma and PD effluent cefalothin concentrations, so more frequent dosing may be required.