Development and validation of an HPLC method for the determination of vancomycin in human plasma and its comparison with an immunoassay (PETINIA)

High throughput analysis of vancomycin in human plasma by UHPLC-MS/MS

An analytical assay based on ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) technique for absolute quantification of vancomycin in complexed biological matrix was developed in this study. Reversed phase column with gradient elution was chosen for chromatographic separation of vancomycin and internal standard (IS) norancomycin. Sample pretreatment was performed by micro-solid phase extraction (μ-SPE) with Oasis® MAX μElution Plate (I.D., 30 μm). Multiple reaction monitoring (MRM) transition was chosen for monitoring of the analytes. For vancomycin, mass-to-charge ratio (m/z) of the MRM transition was 725.3→144.1; For norvancomycin, m/z of the MRM transition was 718.3→144.2. The running time was 3 minutes for each sample. The UHPLC-MS/MS method showed a good linear relationship (R2≥0.995) in the concentration range of 0.5-100 μg/mL. The intra- and inter-day accuracies (relative error, RE) are within the range of -3.44 %-1.50 % and precisions are between 3.48 % and 10.19 %. μ-SPE could enrich the analytes and decrease the endogenous interferences, thereby improving the selectivity and sensitivity of the method. The analytical assay is selective, accurate and reproducible. The assay was successfully applied to therapeutic drug monitoring of vancomycin in clinical application.

The Development and Validation of a Simple HPLC-UV Method for the Determination of Vancomycin Concentration in Human Plasma and Application in Critically Ill Patients

Vancomycin is an antimicrobial agent that exhibits high efficacy against Gram-positive bacteria. The importance of therapeutic drug monitoring (TDM) for vancomycin has been substantiated in specific patient cohorts, underscoring the significance of determining vancomycin plasma levels. This study presents the development and validation of a simple, reproducible, and practical approach for quantifying vancomycin levels in human plasma samples through high-performance liquid chromatography (HPLC). Deproteinization of plasma samples (0.3 mL) was achieved using 10% perchloric acid. The chromatographic separation was achieved using a C18 column. The mobile phase, consisting of phosphate buffer and acetonitrile (90:10, v/v), was run at a flow rate of 1 mL/min. Ultraviolet detection was conducted at a wavelength of 192 nm and the method was linear in the range of 4.5-80 mg/L (r2 > 0.99). Inter- and intra-day assay precision and accuracy were determined to be within the acceptable range. The run time was noted to be 10 min. This method was evaluated using different greenness tools, which indicated that the method is environmentally friendly. Our method was effectively applied to analyze vancomycin concentrations in critically ill patients. Thus, our approach has the potential for practical implementation in routine TDM procedures.

Factors affecting free vancomycin concentration and target attainment of free area under the concentration-time curve

BACKGROUND

It has been reported that the protein binding rate of vancomycin (VCM) varies among individual patients. So, the authors investigated relevant factors that may affect free VCM concentration and target attainment of free area under the concentration-time curve (fAUC).

METHODS

Thirty-nine patients were included. Multiple regression analysis was performed to determine the valuable factors in the free VCM concentration, and the target attainment of area under the concentration-time curve (AUC) 400-600 mg・h/L and fAUC200-300 mg・h/L was calculated.

RESULTS

We found total protein was significant covariate for free VCM. Among 18 patients who were investigated for AUC and fAUC estimation, 9 patients (50.0%) and 12 patients (66.7%) reached AUC > 600 mg・h/L, and fAUC > 300 mg・h/L (p = 0.310), respectively.

CONCLUSIONS

Total protein is a significant predictor for free VCM estimation. And the fAUC-guided TDM for VCM TDM may contribute to more strict dosing than the AUC-guided TDM in hyper- or hypo-proteinemic population.

TRIAL REGISTRATION

Retrospectively registered.

Therapeutic Monitoring of Vancomycin Implemented by Eremomycin ELISA

BACKGROUND/OBJECTIVES

Due to a narrow therapeutic window, side-effects, toxicities, and individual pharmacokinetics (PK) variability, WHO classifies vancomycin (VCM) as a "watch antibiotic" whose use should be monitored to improve clinical effectiveness. Availability and ease of use have made the immunoassay technique the basic tool for the therapeutic drug monitoring (TDM) of VCM concentrations.

METHODS

The present study describes the development of a TDM tool for VCM based on anti-eremomycin (ERM) antibody enzyme-linked immunosorbent assay (ELISA).

RESULTS

The optimized assay format based on coating a BSA-VCM conjugate allowed for the equal recognition of both VCM and ERM (100 and 104%) and was not influenced by concomitant antibiotics. Among the sample pretreatments studied, acetonitrile deproteinization was preferred to effectively remove the most likely matrix interferences and to provide 75-96% VCM recovery in the range of 3-30 mg/L, ensuring reliable determination of the key PK parameter, Ctrough. Higher peak concentrations were measured in more diluted samples. Several inflammatory indices, biochemical markers, and key proteins significantly different from normal in critically ill patients were investigated as assay interferers and were found not to interfere with VCM analysis. Serum samples (n = 108) from patients (n = 4) with extensive burn injuries treated with combined antibiotic therapy were analyzed for VCM using the developed assay and confirmed by LC-MS/MS, demonstrating good agreement.

CONCLUSIONS

The approach used shows that the same analytical instrument is suitable for measuring structurally related analytes and is fully adequate for their therapeutic monitoring. Suboptimal exposure based on Ctrough values obtained with standard dosing regimens supports the use of TDM in these patients.

Recent Trends in Therapeutic Drug Monitoring of Peptide Antibiotics

Antimicrobial peptides take a specific position in the field of antibiotics (ATBs), however, from a large number of available molecules only a few of them were approved and are used in clinics. These therapeutic modalities play a crucial role in the management of diseases caused by multidrug-resistant bacterial pathogens and represent the last-line therapy for bacterial infections. Therefore, there is a demand for a rationale use of such ATBs based on optimization of the dosing strategy to minimize the risk of resistance and ensure the sustainable efficacy of the drug in real clinical practice. Therapeutic drug monitoring, as a measurement of drug concentration in the body fluids or tissues, results in the optimization of the patient´s medication and therapy outcome. This strategy is beneficial and could result in tailored therapy for different types of infection and the prolongation of the use and efficacy of ATBs in hospitals. This review paper provides an actual overview of approved antimicrobial peptides used in clinical practice and covers current trends in their analysis by convenient and advanced methodologies used for their identification and/or quantitation in biological matrices for therapeutic drug monitoring purposes. Special emphasis is given to the methods with perspective clinical outcomes.

Comparison of vancomycin assays in patients undergoing hemodialysis

Vancomycin is a glycopeptide antibiotic mainly excreted by glomerular filtration. Therefore, patients undergoing hemodialysis tend to accumulate its crystalline degradation product, which has been associated with cross-reaction in commercial immunoassays. The aim of this study was to assess the performance of two commercial immunoassays for measuring vancomycin levels in patients undergoing hemodialysis. This method-comparison study enrolled patients undergoing hemodialysis at two hospitals in Porto Alegre, Brazil. Vancomycin serum concentrations measured by Chemiluminescent Microparticle Assay (CMIA) and measured by Kinetic Interaction of Microparticles in Solution (KIMS) were compared with Liquid Chromatography coupled with Tandem Mass Spectrometry (LC-MS/MS). A total of 64 samples from 42 patients and 54 samples from 23 patients were included in CMIA and KIMS groups. Both measurements were highly correlated with LC-MS/MS, with Spearman rank correlation coefficient r = 0.840 (p < 0.001) and r = 0.926 (p < 0.001), respectively. No deviation of linearity was observed (p = 0.81 and p = 0.49, respectively). The mean difference between CMIA and LC-MS/MS was -1.19 μg/mL and between KIMS and LC-MS/MS was -2.28 μg/mL. LC-MS/MS measured levels were, on average, 2.64 % higher than CMIA and 8.81 % higher than KIMS. CMIA and KIMS revealed accurate commercial methods to measure vancomycin serum concentrations in patients undergoing hemodialysis.

Electrochemical and optical (bio)sensors for analysis of antibiotic residuals

Antibiotic residuals in foods may lead to crucial health and safety issues in the human body. Rapid and in-time analysis of antibiotics using simple and sensitive techniques is in high demand. Among the most commonly applicable modalities, chromatography-based techniques like HPLC and LC-MS, along with immunological approaches, particularly ELISA have been exampled in the analysis of antibiotics. Despite being highly sensitive, these methods are considerably time-consuming, thus the presence of skilled personnel and costly equipment is essential. Nanomaterial-based (bio)sensors, however, are de novo analytical equipment with some beneficial characteristics, such as simplicity, low price, on-site, high accuracy, and sensitivity for the detection of analytes. This review aimed to collect the latest developments in NM-based sensors and biosensors for the observation of highly used antibiotics like Vancomycin (Van), Linezolid (Lin), and Clindamycin (Clin). The current challenges and developmental perspectives are also debated in detail for future research directions.

Electrospun Chitosan-Based Nanofibrous Coating for the Local and Sustained Release of Vancomycin

As the population ages, the number of vascular surgery procedures performed increases. Older adults often have multiple comorbidities, such as diabetes and hypertension, that increase the risk of complications from vascular surgery including vascular graft infection (VGI). VGI is a serious complication with significant morbidity, mortality, and healthcare costs. Here, we aimed to develop a nanofibrous chitosan-based coating for vascular grafts loaded with different concentrations of the vancomycin antibiotic vancomycin (VAN). Blending chitosan with poly(vinyl alcohol) or poly(ethylene oxide) copolymers improved solubility and ease of spinning. Thermal gravimetric analysis and Fourier transform infrared spectroscopy confirmed the presence of VAN in the nanofibrous membranes. Kinetics of VAN release from the nanofibrous mats were evaluated using high-performance liquid chromatography, showing a burst followed by sustained release over 24 h. To achieve longer sustained release, a poly(lactic-co-glycolic acid) coating was applied, resulting in extended release of up to 7 days. Biocompatibility assessment using human umbilical vein endothelial cells demonstrated successful attachment and viability of the nanofiber patches. Our study provides insights into the development of a drug delivery system for vascular grafts aimed at preventing infection during implantation, highlighting the potential of electrospinning as a promising technique in the field of vascular surgery.

Poor removal of tedizolid during continuous hemodiafiltration: experiments using an in vitro continuous hemodiafiltration model

BACKGROUND

Tedizolid is an oxazolidinone anti-MRSA drug with included in the National Health Insurance Drug Price List in 2018. The effect of hemodialysis on tedizolid phosphate concentrations has been reported; pre-dialysis concentrations decreased by 10% compared to post- dialysis concentrations. However, the material of the dialysis membrane remains unknown. In addition, there have been no reports on the effects of continuous hemodiafiltration. In this study, we investigated the effects of continuous hemodiafiltration on tedizolid using two types of dialysis membranes made of different materials.

METHODS

The adsorption of tedizolid, linezolid, and vancomycin to two different dialysis membranes was investigated, and the clearance of each drug was calculated by experiments using an in vitro continuous hemodiafiltration model.

RESULTS

The adsorption of tedizolid, linezolid, and vancomycin on the dialysis membranes was examined, and no adsorption was observed. Experimental results from the continuous hemodiafiltration model showed that linezolid and vancomycin concentrations decreased over time: after two hours, the respective decreases were 26.48 ± 7.14% and 28.51 ± 2.32% for polysulfone membranes, respectively. The decrease was 23.57 ± 4.95% and 28.73 ± 5.13% for the polymethylmethacrylate membranes, respectively. These results suggested that linezolid and vancomycin were eliminated by continuous hemodiafiltration. In contrast, tedizolid phosphate and tedizolid concentrations decreased slightly in the polysulfone and polymethylmethacrylate membranes. The decrease in concentrations were 2.10 ± 0.77% and 2.97 ± 0.60% for the polysulfone membranes, respectively. For the polymethylmethacrylate membranes, the decrease in concentration were 2.01 ± 0.88% and 1.73 ± 0.27%, respectively.

CONCLUSION

These results suggested that tedizolid should not be considered for dose control during continuous hemodiafiltration.

Development and validation of a dried plasma spot LC-MS/MS method for therapeutic monitoring of vancomycin and comparison with enzyme-multiplied immunoassay

Vancomycin is used as an antimicrobial agent for the treatment of severe gram-positive infections. The importance of therapeutic monitoring of antimicrobials has led to the development of more specific sample preparation techniques capable of identifying with accuracy the concentration of this substance in the organism. An aliquot of 10 μl of plasma was transferred to Whatman 903 paper and dried at room temperature. The extraction method was performed by cutting and transferring the paper to a microtube and adding sodium phosphate buffer and internal standard. The mixture was shaken and centrifuged, and a 5-μl aliquot was injected into the analytical system. The optimization of the main parameters that can influence the extraction efficiency was performed using multivariate approaches to obtain the best conditions. The method developed was validated, providing coefficients of determination higher than 0.994 and a lower limit of quantification of 1 mg/L. Within- and between-run precision ranged from 11.4 to 17.30% and from 6.65 to 13.51%, respectively. This method was successfully applied to 75 samples of patients undergoing vancomycin therapy. The method was rapid, simple, and environmentally friendly with satisfactory analytical performance and was advantageous over the laborious and time-consuming methodologies used in therapeutic drug monitoring routine analyses.

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.

Pharmacokinetic assessment of vancomycin in critically ill patients and nephrotoxicity prediction using individualized pharmacokinetic parameters

Introduction: Therapeutic drug monitoring (TDM) and pharmacokinetic assessments of vancomycin would be essential to avoid vancomycin-associated nephrotoxicity and obtain optimal therapeutic and clinical responses. Different pharmacokinetic parameters, including trough concentration and area under the curve (AUC), have been proposed to assess the safety and efficacy of vancomycin administration. Methods: Critically ill patients receiving vancomycin at Nemazee Hospital were included in this prospective study. Four blood samples at various time intervals were taken from each participated patient. Vancomycin was extracted from plasma samples and analyzed using a validated HPLC method. Results: Fifty-three critically ill patients with a total of 212 blood samples from June 2019 to June 2021 were included in this study. There was a significant correlation between baseline GFR, baseline serum creatinine, trough and peak concentrations, AUCτ, AUC24h, Cl, and Vd values with vancomycin-induced AKI. Based on trough concentration values, 66% of patients were under-dosed (trough concentration <15 μg/ml) and 18.9% were over-dosed (trough concentration ≥20 μg/ml). Also, based on AUC24h values, about 52.2% were under-dosed (AUC24h < 400 μg h/ml), and 21.7% were over-dosed (AUC24h > 600 μg h/ml) that emphasizes on the superiority of AUC-based monitoring approach for TDM purposes to avoid nephrotoxicity occurrence. Conclusion: The AUC-based monitoring approach would be superior in terms of nephrotoxicity prediction. Also, to avoid vancomycin-induced AKI, trough concentration and AUCτ values should be maintained below the cut-off points.

Concurrent estimation of some co-administered antimicrobial drugs applying conventional and first derivative synchronous fluorescence spectroscopy techniques

For the estimation of some co-administered antimicrobials, two highly accurate and precise spectrofluorimetric methods were developed. Fluconazole (FLZ) is co-administered with either ciprofloxacin (CPR) or ofloxacin (OFX) for the treatment of certain microbial infections. On the other hand, another antimicrobial drug, vancomycin (VNC) is co-administered with ciprofloxacin (CPR) for peritonitis treatment. In method I, conventional spectrofluorimetry has been introduced for the concurrent quantitative estimation of FLZ in presence of OFX or CPR. While in method II, a first derivative synchronous spectrofluorimetric technique was adapted for quantitation of VNC and CPR co-administered combination. Both of them were utilized for estimation of the considered drugs in raw materials, laboratory prepared mixtures, dosage forms, and biological fluids. Method I was relied on simultaneous measuring of the native fluorescence of FLZ and OFX or CPR without any overlapping between the emission spectra of each binary mixture (FLZ / OFX) and (FLZ / CPR). Fluorescence intensities were measured at 283.0, 483.0 and 436.0 nm after excitation at 262.0, 292.0 and 275.0 nm for FLZ, OFX and CPR, respectively. Method II was utilized the synchronous fluorescence intensity of VNC and CPR in methanol at Δλ = 40 nm. The first derivative synchronous spectra were calibrated at 297.0 nm for VNC and at 379.5 nm for CPR. Different variables influencing conventional and synchronous fluorescence intensities of the four antimicrobials under investigation were precisely optimized. Both methods were successfully investigated for the determination of the studied drugs in plasma. The linear data analysis for the calibration curves reveals a good relationship in the ranges of 1.0-10.0, 0.25-2.5 and 0.06-0.6 μg/mL for FLZ, OFX and CPR for method I with limits of detection 0.144, 0.038 and 0.007 μg/mL and limits of quantitation of 0.437, 0.114 and 0.021 μg/mL for FLZ, OFX and CPR, respectively. Linearity range for method II was 0.5 -10.0 μg/mL for VNC and CPR with detection limits of 0.127 and 0.110 μg/mL and quantitation limits of 0.380 and 0.334 μg/mL for VNC and CPR, respectively. International Council on Harmonization ICH Q2 (R1) Guidelines were followed in the developed methods validation. The achieved outcomes were statistically compared with those found by the reported ones, and no significant difference was observed.

Dose Tailoring of Vancomycin Through Population Pharmacokinetic Modeling Among Surgical Patients in Pakistan

Background: Vancomycin is a narrow therapeutic agent, and it is necessary to optimize the dose to achieve safe therapeutic outcomes. The purpose of this study was to identify the significant covariates for vancomycin clearance and to optimize the dose among surgical patients in Pakistan. Methods: Plasma concentration data of 176 samples collected from 58 surgical patients treated with vancomycin were used in this study. A population pharmacokinetic model was developed on NONMEM^® using plasma concentration-time data. The effect of all available covariates was evaluated on the pharmacokinetic parameters of vancomycin by stepwise covariate modeling. The final model was evaluated using bootstrap, goodness-of-fit plots, and visual predictive checks. Results: The pharmacokinetics of vancomycin followed a one-compartment model with first-order elimination. The vancomycin clearance (CL) and volume of distribution (Vd) were 2.45 L/h and 22.6 l, respectively. Vancomycin CL was influenced by creatinine clearance (CRCL) and body weight of the patients; however, no covariate was significant for its effect on the volume of distribution. Dose tailoring was performed by simulating dosage regimens at a steady state based on the CRCL of the patients. The tailored doses were 400, 600, 800, and 1,000 mg for patients with a CRCL of 20, 60, 100, and 140 ml/min, respectively. Conclusion: Vancomycin CL is influenced by CRCL and body weight of the patient. This model can be helpful for the dose tailoring of vancomycin based on renal status in Pakistani patients.

Desalting Paper Spay Mass Spectrometry (DPS-MS) for Rapid Detection of Glycans and Glycoconjugates

The detection of glycans and glycoconjugates has gained increasing attention in biological fields. Traditional mass spectrometry (MS)-based methods for glycoconjugate analysis are challenged with poor intensity when dealing with complex biological samples. We developed a desalting paper spray mass spectrometry (DPS-MS) strategy to overcome the issue of signal suppression of carbohydrates in salted buffer. Glycans and glycoconjugates (i.e., glycopeptides, nucleotide sugars, etc.) in non-volatile buffer (e.g., Tris buffer) can be loaded on the paper substrate from which buffers can be removed by washing with ACN/H2O (90/10 v/v) solution. Glycans or glycoconjugates can then be eluted and spray ionized by adding ACN/H2O/formic acid (FA) (10/90/1 v/v/v) solvent and applying a high voltage (HV) to the paper substrate. This work also showed that DPS-MS is applicable for direct detection of intact glycopeptides and nucleotide sugars as well as determination of glycosylation profiling of antibody, such as NIST monoclonal antibody IgG (NISTmAb). NISTmAb was deglycosylated with PNGase F to release N-linked oligosaccharides. Twenty-six N-linked oligosaccharides were detected by DPS-MS within a 5-minute timeframe without the need for further enrichment or derivatization. This work demonstrates that DPS-MS allows fast and sensitive detection of glycans/oligosaccharides and glycosylated species in complex matrices and has great potential in bioanalysis.

Engineering mesoporous silica nanoparticles towards oral delivery of vancomycin

Vancomycin (Van) is a key antibiotic of choice for the treatment of systemic methicillin resistant Staphylococcus aureus (MRSA) infections. However, due to its poor membrane permeability, it is administered parenterally, adding to the cost and effort of treatment. The poor oral bioavailability of Van is mainly due to its physico-chemical properties that limit its paracellular and transcellular transport across gastrointestinal (GI) epithelium. Herein we report the development of silica nanoparticles (SNPs)-based formulations that are able to enhance the epithelial permeability of Van. We synthesized SNPs of different pore sizes (2 nm and 9 nm) and modified their surface charge and polarity by attaching different functional groups (-NH₂, -PO₃, and -CH₃). Van was loaded within these SNPs at a loading capacity in the range of ca. 18-29 wt%. The Van-loaded SNPs exhibited a controlled release behaviour when compared to un-encapsulated Van which showed rapid release due to its hydrophilic nature. Among Van-loaded SNPs, SNPs with large pores showed a prolonged release compared to SNPs with small pores while SNPs functionalised with -CH₃ groups exhibited a slowest release among the functionalised SNPs. Importantly, Van-loaded SNPs, especially the large pore SNPs with negative charge, enhanced the permeability of Van across an epithelial cell monolayer (Caco-2 cell model) by up to 6-fold, with P_app values up to 1.716 × 10^-5 cm s^-1 (vs. 0.304 × 10^-5 cm s^-1 for un-encapsulated Van) after 3 h. The enhancement was dependent on both the type of SNPs and their surface functionalisation. The permeation enhancing effect of SNPs was due to its ability to transiently open the tight junctions measured by decrease in transepithelial resistance (TEER) which was reversible after 3 h. All in all, our data highlights the potential of SNPs (especially SNPs with large pores) for oral delivery of Van or other antimicrobial peptides.

Catalysis of electro-oxidation of antibiotics by nitroxyl radicals and the electrochemical sensing of vancomycin

Quantifying drug concentrations in vivo quickly and easily is possible using electrochemical methods. The present study describes the electrochemical detection of vancomycin (VCM) and other antibiotics from the current obtained using nitroxyl radicals as electrocatalysts. Nortropine N-oxyl (NNO), which is more active than 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO), a typical nitroxyl radical compound, produced greater current values for drugs with intramolecular hydroxy groups and secondary and tertiary amines. However, because the catalytic action of NNO is inactivated by primary amines in the substrate, VCM and teicoplanin with primary amines could not be detected. TEMPO was less active than NNO but not inactivated against primary amines. Therefore, electrochemical sensing of vancomycin was done using 4-acetamido-2,2,6,6-tetramethylpiperidine 1-oxyl (A-TEMPO), which has a greater oxidation capacity than TEMPO due to its electron-withdrawing groups. As a result, the current of A-TEMPO increased in the low concentration range of VCM as compared to TEMPO. This method also was able to quantify VCM in the concentration range of 10-100 μM, which is an important concentration range for drug monitoring in blood.

Investigation of some univariate and multivariate spectrophotometric methods for concurrent estimation of Vancomycin and Ciprofloxacin in their laboratory prepared mixture and application to biological fluids

Four simple, rapid, accurate and precise spectrophotometric methods were established and validated in accordance with ICH Q2 (R1) guidelines for the simultaneous determination of Vancomycin (VNC) and Ciprofloxacin (CPR) in their raw materials, laboratory prepared mixtures and pharmaceutics. Method A depends on using first derivative spectrophotometry (D¹) where VNC and CPR were resolved at 243.6 and 262.0 nm, respectively. Concerning method B, it is based on utilizing first derivative of ratio spectra (DD¹) where determination was performed at the peak maxima at 244.0 nm and 258.0 nm for VNC and CPR, respectively. Two chemometric models were applied for the quantitative analysis of both drugs in their laboratory prepared mixtures, namely, partial least squares (PLS) (method C) and artificial neural network (ANN) (method D). For univariate methods linearity range for both drugs was in the range of 3-30 and 1-10 μg/mL for VNC and CPR, respectively. Multivariate calibration methods using five level, two factor calibration model for the development of 25 mixtures were also applied for the simultaneous estimation of the two drugs in their laboratory prepared mixture using spectral region from 200.0 to 300.0 nm using interval 1 nm. The suggested methods have been successfully extended to the assay of the two studied drugs in laboratory-prepared mixtures and pharmaceuticals with excellent recovery. First derivative spectrophotometry (D¹) was also applied for the assay of both analytes in spiked human plasma with good recovery. No interaction with common pharmaceutical additives has been observed which indicate the selectivity of the method. The results obtained were favourably compared with those obtained applying the reported methods. The methods are validated in compliance with the ICH Q2 (R1) guidelines and the measured accuracy and precision are assessed to be within the accepted limits.

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.

A simple and validated HPLC method for vancomycin assay in plasma samples: the necessity of TDM center development in Southern Iran

BACKGROUND AND PURPOSE

Vancomycin is a glycopeptide antibiotic which is the drug of choice against methicillin-resistant Staphylococcus aureus. It has a narrow therapeutic index, and thus therapeutic drug monitoring (TDM), and clinical pharmacokinetic assessment are necessary in order to prevent adverse drug reactions such as nephrotoxicity. In this study, we aimed to develop a simple and validated HPLC method for vancomycin assay in order to establish a TDM center for patients admitted to the ICU of Nemazee Hospital in southern Iran.

EXPERIMENTAL APPROACH

In this study, a brief review of different parameters and variables which could affect the sensitivity, selectivity of the validated HPLC method for vancomycin determination were considered. According to the previous studies a simple, fast, and the relatively low-cost method was established for vancomycin determination in plasma samples.

FINDINGS/RESULTS

The developed HPLC assay indicated a calibration curve with R-square of > 0.999, acceptable selectivity, the accuracy of 90-105%, CV% of less than 15%, the limit of quantification of 1 μg/mL, and limit of detection of 300 ng/mL. Vancomycin trough level, the area under the curve, renal clearance, the volume of distribution, and elimination constant were measured in patients using this validated method.

CONCLUSION AND IMPLICATIONS

Validated method for assay of vancomycin plasma levels was used to quantify vancomycin levels of four patients who were admitted to the ICU of Nemazee Hospital. According to the results, two of these patients showed lower levels than recommended therapeutic purposes while one of them showed a toxic level. According to the results, the TDM assessment of vancomycin is strongly recommended for patients who are hospitalized in ICU.

Current Status of Vancomycin Analytical Methods

BACKGROUND

The glycopeptide antibiotics are a class of antimicrobial drugs that are an important alternative for cases of bacterial infections resistant to penicillins, besides being able to be used to treat infections in people allergic to pencilin. They have great activity against Gram-positive microorganisms, including methicillin-resistant Staphylococcus aureus (MRSA), by inhibiting the cell wall synthesis.

OBJECTIVE

There are many analytical methods in the literature for determination of antimicrobial glycopeptide vancomycin in different matrixes that are very effective; however, all of them use toxic solvents, contributing to the generation of waste, causing damage to the environment and to the operator, as well as increased costs of analysis.

RESULTS

The most prevailing method found was high performance liquid chromatography (HPLC), followed by microbiological assays and, in less quantity, spectrometric methods. The chromatographic methods use organic solvents that are toxic, such as acetonitrile and methanol, and buffer solutions, that can damage the equipment and the column. In the microbiological assays the disc diffusion methods are still in the majority. The spectrophotometric methods were based in the UV-Vis region using buffer solutions as a diluent.

CONCLUSIONS

All these methods can become greener, following green analytical chemistry principles, which could bring benefits both to the environment and the operator, and reduce costs.

HIGHLIGHTS

In this paper, a literature review regarding analytical methods for determination of vancomycin was carried out with a suggestion of greener alternatives.

Vancomycin and creatinine determination in dried blood spots: Analytical validation and clinical assessment

This study aims to develop a liquid chromatography tandem-mass spectrometry (LC-MS/MS) method for vancomycin and creatinine measurement in dried blood spots (DBS) and to evaluate its clinical application. The analytes were extracted from DBS and analyzed by LC-MS/MS. Vancomycin and creatinine DBS and plasma concentrations were compared in 54 and 35 samples, respectively, from 29 patients. Accuracy was 94.4-102.6%, intra-assay precision was 2.1-5.6%, and inter-assay precision was 3.5-7.0%. Patients vancomycin plasma to DBS concentration ratios were highly variable (1.148-5.022), differently from creatinine (0.800-1.283). The assay has adequate analytical performance. Plasma concentrations can be satisfactorily predicted from DBS measurements for creatinine, but not for vancomycin, which limits its clinical application.

Brain Microdialysis Study of Vancomycin in the Cerebrospinal Fluid After Intracerebroventricular Administration in Mice

Vancomycin (VCM) is an important antibiotic for treating methicillin-resistant Staphylococcus aureus (MRSA) infections. To treat bacterial meningitis caused by MRSA, it is necessary to deliver VCM into the meninges, but the rate of VCM translocation through the blood-brain barrier is poor. Additionally, high doses of intravascularly (i.v.) administered VCM may cause renal impairments. Thus, VCM is sometimes administered intracerebroventricularly (i.c.v.) for clinical treatment. However, information on the VCM pharmacokinetics in cerebrospinal fluid (CSF) after i.c.v. administration is lacking. In the present study, we evaluated the VCM pharmacokinetics in the CSF and systemic circulation after i.c.v. compared to that after i.v. administration, using the brain microdialysis method in mice. VCM administered via i.c.v. showed a highly selective distribution in the CSF, without migration to systemic circulation. Moreover, to assess renal impairments after i.c.v. administration of VCM, we histologically evaluated damage to the mouse kidney by hematoxylin and eosin staining. No significant morphological change in the kidney was observed in the i.c.v. administration group compared to that in the i.v. administration group. Our results demonstrate that i.c.v. administration of VCM can be partially prevented from entering the systemic circulation to prevent renal impairments caused by VCM.

A Novel Method for the Determination of Vancomycin in Serum by High-Performance Liquid Chromatography-Tandem Mass Spectrometry and Its Application in Patients with Diabetic Foot Infections

A novel, precise, and accurate high-performance liquid chromatography-tandem mass spectrometry (Q-trap-MS) method was developed, optimized, and validated for determination of vancomycin in human serum using norvancomycin as an internal standard. Effect of different parameters on the analysis was evaluated. ZORBAX SB-C18 column (150 × 4.6 mm, 5 μm) using water (containing 0.1% formic acid, v/v)⁻acetonitrile (containing 0.1% formic acid, v/v) as a mobile phase was chosen. The calibration curve was linear over the concentration ranges of 1 to 2000 ng/mL for vancomycin. The limit of detection (LOD) and limit of quantification (LOQ) for vancomycin were 0.3 and 1.0 ng/mL. Recoveries were between 87.2 and 102.3%, which gave satisfactory precision. A total of 100 serum samples (from 50 patients with diabetic foot proven Gram-positive infection and 50 nondiabetic patients with pneumonia requiring hospitalization and antibiotic therapy) were analyzed by this method. The trough vancomycin concentrations of diabetic foot infection (DFI) patients and nondiabetic patients were 8.20 ± 2.83 μg/mL (range: 4.80⁻14.2 μg/mL) and 15.80 ± 5.43 μg/mL (range: 8.60⁻19.5 μg/mL), respectively. The method is sensitive, precise, and reproducible, it could be applied for routine laboratory analysis of vancomycin in serum samples.

A Rapid and Simple HPLC Method for Therapeutic Monitoring of Vancomycin

Therapeutic monitoring of the antibiotic vancomycin is important to achieve specific plasma concentration and prevent toxic effects. Several assays have been described for vancomycin determination in clinical practice, but high-performance liquid chromatography is still considered the gold standard for the quantification of vancomycin. In this study, we developed a new and rapid high-performance liquid chromatography method requiring 50 μL of plasma for the quantification of vancomycin. Acetonitrile was used for processing plasma by protein precipitation (1:2.5). Isocratic chromatographic analysis was carried out on a C18 silica-based (2.7 μm) column with the mobile phase containing 20 mM ammonium acetate/formic acid buffer (pH 4.0):methanol 88:12 (v/v). A diode array detector was used for UV detection at 240 nm. This method was validated according to the Brazilian Health Surveillance Agency legislation and International Conference on Harmonization guidelines. The measurement range was 1-100 μg/mL, analysis time was 8 min, and intermediate precision was <12%, supporting the present method as a fast, simple, and effective alternative for therapeutic monitoring of vancomycin.

Continuous intravenous vancomycin in children with normal renal function hospitalized in hematology-oncology: prospective validation of a dosing regimen optimizing steady-state concentration

Continuous intravenous (IV) infusion has been shown to be the best option to administer vancomycin because of its time-dependent bactericidal activity. Available IV vancomycin dosing guidelines in pediatrics with normal renal function leads to less than 50% of patients achieving a vancomycin serum concentration (Css) in the target range (15-20 mg/L). The primary objective of this study was to prospectively validate an age-based dosing regimen in pediatric oncology-hematology. The secondary objective was to investigate the influence on Css attainment of different variables. A continuous IV dosing nomogram was built by retrospective study (2000-2010) on Bayesian dosing adjustments performed in 161 patients. This study assessed the prospective validation of this age-based nomogram and the influence on Css attainment of variables as the gender, underlying disease (oncology or hematology), and hematopoietic stem cell transplantation (HSCT) before receiving vancomycin therapy. A total of 94 patients aged from 4.3 months to 17.9 years old with normal renal function were eligible for the prospective validation. Fifty-five of those patients (58.5%) achieved the target range of vancomycin Css. There was no significant difference between age groups (P = 0.816) and no influence of gender (P = 0.500). There was a nonsignificant trend to a better target attainment in oncology patients (69.2% vs. hematology 54.4%, P = 0.142) and patients who did not undergo HSCT (63.3% vs. 33.3%, P = 0.031). This study proposed an age-based nomogram prospectively validated which near 60% of patients of each age class achieving the target range of Css.

Development of a Physiologically Based Pharmacokinetic Modelling Approach to Predict the Pharmacokinetics of Vancomycin in Critically Ill Septic Patients

BACKGROUND AND OBJECTIVES

Sepsis is characterised by an excessive release of inflammatory mediators substantially affecting body composition and physiology, which can be further affected by intensive care management. Consequently, drug pharmacokinetics can be substantially altered. This study aimed to extend a whole-body physiologically based pharmacokinetic (PBPK) model for healthy adults based on disease-related physiological changes of critically ill septic patients and to evaluate the accuracy of this PBPK model using vancomycin as a clinically relevant drug.

METHODS

The literature was searched for relevant information on physiological changes in critically ill patients with sepsis, severe sepsis and septic shock. Consolidated information was incorporated into a validated PBPK vancomycin model for healthy adults. In addition, the model was further individualised based on patient data from a study including ten septic patients treated with intravenous vancomycin. Models were evaluated comparing predicted concentrations with observed patient concentration-time data.

RESULTS

The literature-based PBPK model correctly predicted pharmacokinetic changes and observed plasma concentrations especially for the distribution phase as a result of a consideration of interstitial water accumulation. Incorporation of disease-related changes improved the model prediction from 55 to 88% within a threshold of 30% variability of predicted vs. observed concentrations. In particular, the consideration of individualised creatinine clearance data, which were highly variable in this patient population, had an influence on model performance.

CONCLUSION

PBPK modelling incorporating literature data and individual patient data is able to correctly predict vancomycin pharmacokinetics in septic patients. This study therefore provides essential key parameters for further development of PBPK models and dose optimisation strategies in critically ill patients with sepsis.

An LC-MS/MS method to determine vancomycin in plasma (total and unbound), urine and renal replacement therapy effluent

AIM

Critical illness and medical interventions, such as renal replacement therapy, can cause changes to vancomycin pharmacokinetics and lead to suboptimal dosing. To comprehensively characterize vancomycin pharmacokinetic a method must measure vancomycin in a range of clinical matrices.

RESULTS

A LC-MS/MS method was developed using hydrophilic interaction liquid chromatography and microsample volumes, where possible. For all matrices, the linear concentration range was 1-100 μg/ml, interassay accuracy and precision was within 15%, and recovery above 80%. No matrix effects were observed. Calibration equivalence may be applied for some matrix combinations.

CONCLUSION

A method for the analysis of vancomycin in plasma (total, unbound), urine and renal replacement therapy effluent, suitable for use in any patient pharmacokinetic study, has been developed and validated.

Simple and rapid quantification of vancomycin in serum, urine and peritoneal/pleural effusion via UHPLC-MS/MS applicable to personalized antibiotic dosing research

Management of the therapy of life-threatening bacterial infection is extremely based on an optimal antibiotic treatment. Achieving the correct vancomycin dosage in blood and target tissues can be complicated in special situations, e.g., where large fluid sequestration and/or acute renal failure occur. A UHPLC-MS/MS method operating in electrospray (ESI) positive ion mode was applied for the determination of vancomycin in serum, urine and peritoneal/pleural effusion. Sample pretreatment was composed of dilution and simple protein precipitation where only a small volume (50μL) of serum, urine or peritoneal/pleural effusion was required. The separation of vancomycin was performed on a Meteoric Core C18 BIO column (100×4.6mm, 2.7μm) by gradient elution with 0.1% formic acid in water and acetonitrile. The total time of analysis was 4.5min. The method was found to be linear in the range of 2-60μM (or 0.5-10μM) for serum, 0.27-10μM (or 2-60μM) for peritoneal/pleural effusion and 25-300μM for urine, which was adequate for the determination of vancomycin in patient samples. The intra- and inter-day precision was below 8% RSD, and accuracy was from 89 to 104%. The UHPLC/MS-MS method offers a fast and reliable approach to determine vancomycin concentrations in three different human body fluid samples (serum, urine and peritoneal/pleural effusion) with a simple sample pretreatment that was the same for all selected specimens. This method should be applicable to large sample series in clinical (pharmacokinetic/pharmacodynamic) studies.

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.