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Measurement of ceftazidime concentration in human plasma by ultra‐performance liquid chromatography‐tandem mass spectrometry. Application to critically ill patients and patients with osteoarticular infections
Abstract
Ceftazidime is an antibiotic belonging to the third generation of the cephalosporin family. It is indicated in the treatment of serious, simple or mixed bacterial infections, and its administration in continuous or intermittent infusion allows optimization of the concentration of antibiotic to keep it above the minimum inhibitory concentration. We developed and validated a chromatographic method by ultra-performance liquid chromatography-tandem mass spectrometry to measure ceftazidime concentration in human plasma. Following extraction with acetonitrile and 1,2-dichloroethane, the chromatographic separation was achieved using an Acquity(®) UPLC(®) BEH™ (2.1x100 mm id, 1.7 µm) reverse-phase C18 column, with a water/acetonitrile linear gradient containing 0.1% formic acid at a 0.4 mL/min flow rate. Ceftazidime and its internal standard (cefotaxime) were detected by electrospray ionization mass spectrometry in positive ion multiple reaction monitoring mode using mass-to-charge transitions of 547.0 → 467.9/396.1 and 456.0 → 395.8/324.1, respectively. The limit of quantification was 0.58 mg/L and linearity was observed in the range 0.58-160 mg/L. Coefficients of variation and absolute relative biases were less than 9.8% and 8.4%. The mean recovery for ceftazidime was (74.4 ± 8.1)%. Evaluation of the matrix effect showed ion enhancement, and no carry-over was observed. The validated method could be applied to daily clinical laboratory practice to measure the concentration of ceftazidime in plasma. This article is protected by copyright. All rights reserved.
This article is protected by copyright. All rights reserved.
... Fifteen published articles included data on the preanalytical stability of ceftazidime. 9,10,[15][16][17][18][19][26][27][28]32,36,[52][53][54] These data are shown in Figure 1F. At room temperature, ceftazidime has been reported to be stable for 8 hours in several studies. ...
... At 2-88C, ceftazidime has been reported to be stable for at least 3 days in several studies. 10,17,19,53 One study found instability at 2-88C after 3 days, 52 which conflicts with the finding of stability for up to 6 days reported in another study. 19 At 2208C, ceftazidime has been reported to be stable for at least 3 weeks. ...
Purpose:
Therapeutic drug monitoring (TDM) is increasingly being used to optimize beta-Lactam antibiotic dosing. As beta-Lactams are inherently unstable, confirming pre-analytical sample stability is critical for reporting reliable results. This review aimed to summarize the published literature on the pre-analytical stability of selected widely prescribed beta-Lactams used in TDM.
Methods:
The published literature (2010-2020) on the pre-analytical stability of flucloxacillin, piperacillin, tazobactam, meropenem, cefalexin, cefazolin, and ceftazidime in human plasma, serum, and whole blood was reviewed. Papers examining pre-analytical stability at room temperature, refrigerated, or frozen (-20°C) using liquid chromatography with mass spectrometry or ultraviolet detection were included.
Results:
Summarizing the available data allowed for general observations to be made, although data were conflicting in some cases (piperacillin, tazobactam, ceftazidime, and meropenem at room temperature, refrigerated, or -20°C) or limited (cefalexin, cefazolin, and flucloxacillin at -20°C). Overall, with the exception of the more stable cefazolin, pre-analytical instability was observed after 6-12 hours at room temperature, 2-3 days when refrigerated, and 1-3 weeks when frozen at -20°C. In all cases, excellent stability was detected at -70°C. Studies focusing on pre-analytical stability reported poorer stability than studies investigating stability as part of method validation.
Conclusion:
Based on this review, as general guidance, clinical samples for beta-Lactam analysis should be refrigerated and analyzed within 2 days or frozen at -20°C and analyzed within 1 week. For longer storage times, freezing at -70°C was required to ensure sample stability. This review highlights the importance of conducting well-designed pre-analytical stability studies on beta-Lactams and other potentially unstable drugs under clinically relevant conditions.
... Several methods for determining ceftazidime in plasma have been used involving ultraviolet (UV) detection (Hanes, Herring, & Wood, 1998;Hassouna & Mohamed, 2018;Isla et al., 2005;Johnson, Vandenbussche, Chio, & Jacobson, 1999;Legrand, Vodovar, Tournier, Khoudour, & Hulin, 2016;Siddiqui et al., 2009;Vinks, Brimicombe, Heijerman, & Bakker, 1997;Yeh et al., 2005). These methods often require larger sample sizes (Isla et al., 2005;Myers & Blumer, 1983;Pinder, Brenner, Swoboda, Weigand, & Hoppe-Tichy, 2017), lack sensitivity (Abdulla, Bahmany, Wijma, van der Nagel, & Koch, 2017;Bellouard et al., 2020;Grabe, Bailie, Eisele, & Frye, 1999;Hanes, Herring, & Wood, 1998;Hassouna & Mohamed, 2018;Isla et al., 2005;Johnson, Vandenbussche, Chio, & Jacobson, 1999;Legrand, Vodovar, Tournier, Khoudour, & Hulin, 2016;Myers & Blumer, 1983;Pinder, Brenner, Swoboda, Weigand, & Hoppe-Tichy, 2017;Rigo-Bonnin et al., 2016;Siddiqui et al., 2009;Vinks, Brimicombe, Heijerman, & Bakker, 1997;Yeh et al., 2005), have complicated extraction methods (Hanes, Herring, & Wood, 1998) et al., 2020;Legrand, Vodovar, Tournier, Khoudour, & Hulin, 2016;Mortensen, Jensen, Zhang, & Doogue, 2019;Rigo-Bonnin et al., 2016;Sillen et al., 2015;Yeh et al., 2005). Siddiqui et al. (2009), Hassouna and Mohamed (2018), Vinks, Brimicombe, Heijerman, and Bakker (1997), Johnson, Vandenbussche, Chio, and Jacobson (1999), Hanes, Herring, andWood (1998), Pinder, Brenner, Swoboda, Weigand, andHoppe-Tichy (2017), Grabe, Bailie, Eisele, and Frye (1999), Myers andBlumer (1983), Isla et al. (2005), Legrand, Vodovar, Tournier, Khoudour, andHulin (2016) andYeh et al. (2005) all utilize UV detection, but their lower limit of quantification (LLOQ), ranging from 0.3 to 500 μg/ml, is greater than that for our method, which is 0.1 μg/ml. ...
... Several methods for determining ceftazidime in plasma have been used involving ultraviolet (UV) detection (Hanes, Herring, & Wood, 1998;Hassouna & Mohamed, 2018;Isla et al., 2005;Johnson, Vandenbussche, Chio, & Jacobson, 1999;Legrand, Vodovar, Tournier, Khoudour, & Hulin, 2016;Siddiqui et al., 2009;Vinks, Brimicombe, Heijerman, & Bakker, 1997;Yeh et al., 2005). These methods often require larger sample sizes (Isla et al., 2005;Myers & Blumer, 1983;Pinder, Brenner, Swoboda, Weigand, & Hoppe-Tichy, 2017), lack sensitivity (Abdulla, Bahmany, Wijma, van der Nagel, & Koch, 2017;Bellouard et al., 2020;Grabe, Bailie, Eisele, & Frye, 1999;Hanes, Herring, & Wood, 1998;Hassouna & Mohamed, 2018;Isla et al., 2005;Johnson, Vandenbussche, Chio, & Jacobson, 1999;Legrand, Vodovar, Tournier, Khoudour, & Hulin, 2016;Myers & Blumer, 1983;Pinder, Brenner, Swoboda, Weigand, & Hoppe-Tichy, 2017;Rigo-Bonnin et al., 2016;Siddiqui et al., 2009;Vinks, Brimicombe, Heijerman, & Bakker, 1997;Yeh et al., 2005), have complicated extraction methods (Hanes, Herring, & Wood, 1998) et al., 2020;Legrand, Vodovar, Tournier, Khoudour, & Hulin, 2016;Mortensen, Jensen, Zhang, & Doogue, 2019;Rigo-Bonnin et al., 2016;Sillen et al., 2015;Yeh et al., 2005). Siddiqui et al. (2009), Hassouna and Mohamed (2018), Vinks, Brimicombe, Heijerman, and Bakker (1997), Johnson, Vandenbussche, Chio, and Jacobson (1999), Hanes, Herring, andWood (1998), Pinder, Brenner, Swoboda, Weigand, andHoppe-Tichy (2017), Grabe, Bailie, Eisele, and Frye (1999), Myers andBlumer (1983), Isla et al. (2005), Legrand, Vodovar, Tournier, Khoudour, andHulin (2016) andYeh et al. (2005) all utilize UV detection, but their lower limit of quantification (LLOQ), ranging from 0.3 to 500 μg/ml, is greater than that for our method, which is 0.1 μg/ml. ...
A simple high‐performance liquid chromatography method for the determination of ceftazidime in plasma has been developed. Using an ultrafiltration technique samples were separated by reverse‐phase high performance liquid chromatography on a Symmetry C18 4.6 x 250 mm column (5.0 μm) and ultraviolet absorbance was measured at 260 nm. The mobile phase was a mixture of 10 mM potassium phosphate monobasic pH 2.5 with phosphoric acid and acetonitrile (90:10). The standard curve ranged from 0.1 – 100 μg/mL. Intra and Inter‐assay variability for ceftazidime was less than 12%, and the average recovery was 89%. The lower limit of quantification was 0.1 μg/mL. This method has been used successfully to analyze frog plasma samples at this institution and it could be applied to other small volume samples in a clinical or research setting.
... In addition, both antibiotics were stable for 6 h after storage at room temperature for 4 h followed by storage at 4 • C after gel separation [12]. Similarly, ceftazidime and flucloxacillin were stable in plasma for 12 h, both at 4 • C on the autosampler and at room temperature (RT) [12,13,47]. Meropenem was stable for 8 h at 4 • C and 3-6 h at RT in both whole blood and plasma, while piperacillin was stable for 48 h in plasma without gel separation [40]. ...
Background:
The aim of this study was to evaluate the CLAM-2000 automated preanalytical sample preparation module with integrated liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) as a method for 24/7 therapeutic drug monitoring (TDM) of beta-lactam antibiotics in routine clinical diagnostics.
Methods:
Method validation was performed using quality control samples. Method comparison was performed with routine samples from patients treated with beta-lactam antibiotics.
Results:
The determination of piperacillin, meropenem, ceftazidime, flucloxacillin, and cefotaxime was performed using D5-piperacillin and D6-meropenem as internal standards. The linearity of the method was within the therapeutic range of beta-lactam antibiotics. The imprecision and accuracy data obtained from quality control samples were within 15%, and the imprecision of patient samples on the instrument was less than the 5% coefficient of variation (CV). Internal standards stored in the instrument at 9 °C for at least one week were stable, which facilitated reagent use and storage.
Conclusion:
The CLAM-2000 (Shimadzu, Kyoto, Japan) provides reproducible results as an established routine instrument and is a useful tool for 24/7 TDM of beta-lactam antibiotics in routine clinical diagnostics.
... Plasma concentrations of all patients were measured together (and double checked on different days) afterward by UPLC-MS/MS. The methodology has been standardized and described previously by our group [27,28]. ...
Purpose:
To validate an easy-to-use method to guide beta-lactams dosage in CI (formula).
Methods:
A retrospective analysis was conducted of a prospectively collected cohort (n = 24 patients) with osteoarticular infections caused by Gram-negative bacilli (GNB) managed with beta-lactams in CI. Beta-lactams dose was calculated using a described formula (daily dose = 24 h × beta-lactam clearance × target "steady-state" concentration) to achieve concentrations above the MIC. We correlated the predicted concentration (Cpred = daily dose/24 h × beta-lactam clearance) with the patient's observed concentration (Cobs) measured by UPLC-MS/MS (Spearman's coefficient).
Results:
The most frequent microorganism treated was P. aeruginosa (21 cases; 9 MDR). Beta-lactams in CI were ceftazidime (n = 14), aztreonam (7), and piperacillin/tazobactam (3), mainly used in combination (12 with colistin, 5 with ciprofloxacin) and administered without notable side effects. The plasma Cobs was higher overall than Cpred; the Spearman correlation between both concentrations was rho = 0.6 (IC 95%: 0.2-0.8) for all beta-lactams, and rho = 0.8 (IC 95%: 0.4-1) for those treated with ceftazidime.
Conclusions:
The formula may be useful in clinical practice for planning the initial dosage of beta-lactams in CI, while we await a systematic therapeutic drug monitoring. The use of beta-lactams in CI was safe.
... Owing to the important intraindividual variability observed in this population, a rapid quantification of several -lactams is requested to allow an efficient and rapid dosage adaptation [22][23][24]. -lactams TDM is usually performed using in-house previously validated chromatographic method according to international guidelines, as European guideline on bioanalytical method validation [25]. ...
β-lactams therapeutic drug monitoring (TDM) appears as an essential tool to ensure the achievement of pharmacokinetic-pharmacodynamic targets and prevent induced toxicity in intensive care unit patients. Indeed, those patients exhibit important pharmacokinetic variabilities that could lead to unpredictable plasma concentrations, potentially associated with poor clinical outcome, development of antibiotic resistance or increased side effects. Here, we report the case of a 48-year-old-patient admitted to intensive care unit and treated by cefepime using TDM. Due to inconsistency between observed cefepime plasma concentrations and patient clinical examination, investigations were started. After analytical tests, we highlighted an underlying analytical interference that overestimated cefepime plasma concentration with our in-house high performance liquid chromatography with ultraviolet detection (HPLC-UV) method. Only the inadequacy between plasmatic concentration and patient situation alerted pharmacologists and clinicians. As we found no previous case in literature, we believe this report must serve as an example of analytical limits that required pharmacologist awareness and expertise in TDM realization.
A sensitive, accurate and precise liquid chromatography (LC) method for the simultaneous determination of ceftazidime and pyridine in human plasma has been developed and validated. Acetonitrile (ACN) was employed to precipitate the proteins in the plasma samples. Chromatographic separation was performed with a Kinetex® C18 (150 mm × 3 mm, 2.6 µm) column with gradient elution. Ammonium formate 20 mM and ACN were mixed in a ratio of 98:2 (v/v) for mobile phase A and 85:15 (v/v) for mobile phase B. Both were adjusted to pH 4.5 with formic acid. The flow rate was 0.4 mL/min. UV detection was performed at 254 nm. Calibration curves were linear in the range from 0.3 to 225 μg/mL for ceftazidime and from 0.2 to 10 μg/mL for pyridine with correlation coefficients ≥ 0.999. Within- and between-run precision and accuracy were satisfactory with coefficients of variation (CV) ≤ 8.0% and deviations ≤ 7.0%, respectively. The method fulfilled all validation criteria prescribed by the European Medicines Agency guidelines. Next, it has been used successfully to analyze plasma samples of patients who received ceftazidime under intermittent and continuous administration. With intermittent administration, the concentration of the antibiotics reached a peak and then dropped quickly, which may be below the minimal inhibitory concentration (MIC). With continuous administration, the concentration of the antibiotics remained stable over 24 h, certainly above the MIC. Although the same tendency in ceftazidime concentration changes over time was observed, a difference in concentration amongst the patients was noticeable. The concentration of pyridine in plasma was negligible.
Background:
Ceftazidime, a third-generation cephalosporin, is widely used in the treatment of lung infections, often given as "off-label" nebulization. There is need for developing a sensitive and robust analytical method to compute aerodynamic properties of ceftazidime following nebulization.
Objective:
The current study entails development of a simple, accurate and sensitive high-performance liquid chromatography method (HPLC) for ceftazidime estimation, employing the principles of analytical quality-by-design (AQbD) and Monte Carlo simulations.
Methods:
Selection of critical material attributes (CMAs) affecting method performance was accomplished by factor screening exercise. Subsequently, the influential CMAs, i.e., mobile phase ratio and flow rate, were systemically optimized using a face-centred cubic design for the chosen critical analytical attributes (CAAs). The factor relationship(s) between CMAs and CAAs was explored employing 3 D-response surface and 2 D-contour plots, followed by numerical as well as graphical optimization, for establishing the optimal chromatographic conditions. The obtained method operable design region was validated by Monte Carlo simulations for defect rate analysis.
Results:
The optimized HPLC conditions for estimating ceftazidime were acetonitrile to acetic acid solution (75:25) as mobile phase at a flow rate of 0.7 mL/min, leading to Rt of 4.5 min and peak tailing ≤ 2. Validation studies, as per ICH Q2(R1) guidance's, demonstrated high sensitivity, accuracy and efficiency of the developed analytical method with LOD of 0.075 and LOQ of 0.227 µg/mL. Application of this chromatographic method was extrapolated for determining aerodynamic performance by nebulizing ceftazidime at flow rate of 15 L/min using next-generation impactor. The study indicated superior performance, sensitivity and specificity of the developed analytical system for quantifying ceftazidime.
Conclusions:
Application of AQbD approach, coupled with Monte Carlo simulations, aided in developing a robust HPLC method for estimation of ceftazidime per se and on various stages of impactor.
Objectives
The pharmacokinetics/pharmacodynamics of beta-lactams in continuous infusion (CI) for biofilm infections by Pseudomonas aeruginosa has not been defined. We evaluated the efficacy of several dosage regimens of CI ceftazidime, with or without colistin, an antibiotic with a potential anti-biofilm effect, against biofilm-embedded P. aeruginosa.
Methods
The reference strain PAO1 and a clinical isolate HUB8 (both ceftazidime- and colistin-susceptible) in mature biofilms were investigated over 54h using a dynamic CDC biofilm reactor. CI dosage regimens were ceftazidime monotherapy (4, 10, 20 and 40 mg/L), colistin monotherapy (3.50 mg/L); and combinations of colistin with ceftazidime (4 or 40 mg/L). Efficacy was evaluated by log10cfu/mL changes and confocal microscopy.
Results
Against PAO1 at 54h, the anti-biofilm activity of ceftazidime monotherapies was slightly higher for ceftazidime 20 mg/L (-2.84 log10cfu/mL) and 40 mg/L (-3.05), but there were no differences against HUB8. Ceftazidime-resistant colonies emerged with 4 mg/L regimens in both strains and with other regimens in PAO1. Colistin monotherapy had significant anti-biofilm activity against HUB8 (-3.07), but lower against PAO1 (-1.12), and colistin-resistant strains emerged. Combinations of ceftazidime-colistin at 54h increased the killing compared to each monotherapy and prevented resistance emergence to both antibiotics; a higher killing was observed with ceftazidime 40 than 4 mg/L combinations (-4.19 vs -3.10 PAO1; -4.71 vs -3.44 HUB8).
Conclusions
This study demonstrated that, with %T>MIC=100%, CI ceftazidime displayed a concentration-dependent killing against P. aeruginosa biofilm, especially with colistin combination. Our results support using high-dosage regimens of CI ceftazidime with colistin against biofilm-associated infections by ceftazidime-susceptible P. aeruginosa.
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 co-trimoxazole. The liquid chromatography assay is based upon use of a column with a pentafluorophenyl-propyl modified and multi-endcapped stationary phase and the coupling to electrospray ionization with a single quadrupole detector. The performances of both assays with multi-level 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 co-trimoxazole 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. This article is protected by copyright. All rights reserved
The pharmacokinetics of beta-lactam antibiotics in intensive care patients may be profoundly altered due to the dynamic, unpredictable pathophysiological changes that occur in critical illness. For many drugs, significant increases in the volume of distribution and/or variability in drug clearance are common. When "standard" beta-lactam doses are used, such pharmacokinetic changes can result in subtherapeutic plasma concentrations, treatment failure, and the development of antibiotic resistance. Emerging data support the use of beta-lactam therapeutic drug monitoring (TDM) and individualized dosing to ensure the achievement of pharmacodynamic targets associated with rapid bacterial killing and optimal clinical outcomes. The purpose of this work was to describe the pharmacokinetic variability of beta-lactams in the critically ill and to discuss the potential utility of TDM to optimize antibiotic therapy through a structured literature review of all relevant publications between 1946 and October 2011. Only a few studies have reported the utility of TDM as a tool to improve beta-lactam dosing in critically ill patients. Moreover, there is little agreement between studies on the pharmacodynamic targets required to optimize antibiotic therapy. The impact of TDM on important clinical outcomes also remains to be established. Whereas TDM may be theoretically rational, clinical studies to assess utility in the clinical setting are urgently required.
A rapid and specific high-performance liquid chromatography method with UV detection (HPLC-UV) for the simultaneous determination
of 12 beta-lactam antibiotics (amoxicillin, cefepime, cefotaxime, ceftazidime, ceftriaxone, cloxacillin, imipenem, meropenem,
oxacillin, penicillin G, piperacillin, and ticarcillin) in small samples of human plasma is described. Extraction consisted
of protein precipitation by acetonitrile. An Atlantis T3 analytical column with a linear gradient of acetonitrile and a pH
2 phosphoric acid solution was used for separation. Wavelength photodiode array detection was set either at 210 nm, 230 nm,
or 298 nm according to the compound. This method is accurate and reproducible (coefficient of variation [CV] < 8%), allowing
quantification of beta-lactam plasma levels from 5 to 250 μg/ml without interference with other common drugs. This technique
is easy to use in routine therapeutic drug monitoring of beta-lactam antibiotics.
Rational dosing of antibiotics in neonates should be based on pharmacokinetic (PK) parameters assessed in specific populations. PK studies of neonates are hampered by the limited total plasma volume, which restricts the sample volume and sampling frequency. Available drug assay methods require large sample volumes and are labor-intensive or time-consuming. The objective of this study was to develop a rapid ultra-performance liquid chromatographic method with tandem mass spectrometry detection for simultaneous quantification of amoxicillin, meropenem, cefazolin, cefotaxime, deacetylcefotaxime, ceftriaxone, and vancomycin in 50 microl of plasma. Cleanup consisted of protein precipitation with cold acetonitrile (1:4) and solvent evaporation before reversed-phase chromatographic separation and detection using electrospray ionization tandem mass spectrometry. Standard curves were prepared over a large dynamic range with adequate limits of quantitation. Intra- and interrun accuracy and precision were within 100% +/- 15% and 15%, respectively, with acceptable matrix effects. Coefficients of variation for matrix effects and recovery were <10% over six batches of plasma. Stability in plasma and aqueous stocks was generally sufficient, but stability of meropenem and ceftriaxone in extracts could limit autosampler capacity. The instrument run time was approximately 3.50 min per sample. Method applicability was demonstrated with plasma samples from an extracorporeal membrane oxygenation-treated neonate. Different beta-lactam antibiotics can be added to this method with additional ion transitions. Using ultra-performance liquid chromatography mass spectrometry, this method allows simple and reliable quantification of multiple antibiotics in 50 microl of plasma for PK studies of neonates.
We developed and applied pharmacokinetic-pharmacodynamic (PK-PD) models to characterize in vitro bacterial rate of killing as a function of ceftazidime concentrations over time. For PK-PD modeling, data obtained during continuous and intermittent infusion of ceftazidime in Pseudomonas aeruginosa killing experiments with an in vitro pharmacokinetic model were used. The basic PK-PD model was a maximum-effect model which described the number of viable bacteria (N) as a function of the growth rate (lambda) and killing rate (epsilon) according to the equation dN/dt = [lambda - epsilon x [Cgamma(EC50gamma + Cgamma)]] N, where gamma is the Hill factor, C is the concentration of antibiotic, and EC50 is the concentration of antibiotic at which 50% of the maximum effect is obtained. Next, four different models with increasing complexity were analyzed by using the EDSIM program (MediWare, Groningen, The Netherlands). These models incorporated either an adaptation rate factor and a maximum number of bacteria (Nmax) factor or combinations of the two parameters. In addition, a two-population model was evaluated. Model discrimination was by Akaike's information criterion. The experimental data were best described by the model which included an Nmax term and a rate term for adaptation for a period up to 36 h. The absolute values for maximal growth rate and killing rate in this model were different from those in the original experiment, but net growth rates were comparable. It is concluded that the derived models can describe bacterial growth and killing in the presence of antibiotic concentrations mimicking human pharmacokinetics. Application of these models will eventually provide us with parameters which can be used for further dosage optimization.
The stability and compatibility of ceftazidime have been examined in the context of its potential use in concentrated solutions
for continuous infusion in patients suffering from severe nosocomial pneumonia and receiving other intravenous medications
by the same route. Ceftazidime stability in 4 to 12% solutions was found satisfactory (<10% degradation) for 24 h if kept
at a temperature of 25°C (77°F) maximum. Studies mimicking the simultaneous administration of ceftazidime and other drugs
as done in clinics showed physical incompatibilities with vancomycin, nicardipine, midazolam, and propofol and a chemical
incompatibility withN-acetylcystein. Concentrated solutions (50 mg/ml) of erythromycin or clarithromycin caused the appearance of a precipitate,
whereas gentamicin, tobramycin, amikacin, isepamicin, fluconazole, ketamine, sufentanil, valproic acid, furosemide, uradipil,
and a standard amino acid solution were physically and chemically compatible.
Cefepime has been examined for stability, potential liberation of degradation products and compatibility with other drugs under conditions mimicking its potential use by continuous infusion in cystic fibrosis and intensive care patients (5-12% w/v solutions; temperatures from 20 to 37 degrees C; 1 h contact at 25 degrees C with other drugs frequently co-administered by intravenous route to these types of patients). Ceftazidime was used as a comparator based on a previous normative study with this antibiotic for the same indications. Based on a limit of max. 10% degradation, cefepime can be considered stable for a maximum of 24 h at 25 degrees C, but for only approximately 14 h at 30 degrees C, and for <10 h at 37 degrees C. Cefepime released so far unidentified degradation products if maintained at >30 degrees C for >12 h as shown from a marked increase in pH and from the development of a strong red-purple colour. Incompatibilities were observed with erythromycin, propofol, midazolam, phenytoin, piritramide, theophylline, nicardipine, N-acetylcysteine and a concentrated solution of dobutamine. We conclude that: (i) cefepime cannot be used safely by continuous infusion if containers are kept for more than a few hours at 37 degrees C (as will be the case for cystic fibrosis patients if using portable pumps carried under clothes); (ii) caution must be exercised in intensive care patients if the temperature and co-administration of other drugs is not kept under tight control. The nature and safety of the cefepime degradation products need to be studied further.
Modern techniques have reduced the frequency of infections that are associated with prosthetic joints, but such infections continue to pose difficult problems in clinical management. Advances in understanding biofilms and the pathogenesis of microbial interactions with the implant have led to more rational approaches to therapy. This review offers guidance in establishing the diagnosis correctly and an algorithm summarizing the appropriate medical and surgical options.
Growth-kill dynamics were characterized in vitro, and the parameter estimates were used to simulate bacterial growth and kill
in vivo using both mouse and human pharmacokinetics. The parameter estimates obtained in vitro predicted a time above the
MIC of between 35 and 38% for a static effect in mice after 24 h of treatment.
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 2.5min. Chromatographic separation was performed on a Waters Acquity UPLC system using a BEH C18 column (1.7μm, 100mm×2.1mm) applying a binary gradient elution of water and methanol both containing 0.1% formic acid and 2mmol/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 100mg/L for amoxicillin and cefuroxime, between 0.5 and 80mg/L for meropenem and ceftazidime, and between 1 and 150mg/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.
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Ceftazidime is a third generation cephalosporin with a broad range of activity. Clavulanic acid is a β-lactamase inhibitor. A fixed dose combination, with the wide spectrum of action of ceftazidime and clavulanic acid’s high stability to β-lactamases has been developed by Ranbaxy Laboratories Limited (India). The present study was planned to predict any interaction between ceftazidime and clavulanic acid which could affect the safety and efficacy of the fixed dose combination. The study was an open label, balanced, randomized two-treatment, two-period, two-sequence, crossover, single-dose comparative pharmacokinetic study under fed conditions. A single intravenous injection of the test product containing a fixed dose combination of ceftazidime 2000 mg and potassium clavulanate 200 mg and the reference product containing ceftazidime 2000 mg only, was administered during each period. Serial blood samples were collected until 12 h post-dose in each period. Ceftazidime and clavulanic acid concentration in plasma were determined using two separate LC-MS/MS methods and then pharmacokinetic parameters were evaluated. No significant difference was seen in the mean Tmax, Cmax, AUC0–t, and AUC0–∞ when the drug was administered as ceftazidime alone and in combination with clavulanic acid. The Confidence Intervals for the log transformed parameters Cmax, AUC0–t and AUC0–∞ were within limits of 80–125% of ceftazidime for the test and reference products. The lack of significant difference between the pharmacokinetic parameters for ceftazidime alone and in the presence of clavulanic acid ruled out any significant interaction between ceftazidime and clavulanic acid.
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.
Liquid chromatography (LC) is a separation technique used in many different areas to aid the identification and quantification of substances in various matrices. LC techniques with various detection modes have been widely used for the sensitive and selective determination of trace amounts of pharmaceutical active compounds in biological samples and their dosage forms. A completely new system design with advanced technology has been developed, called ultra high performance liquid chromatography, which has evolved from high performance liquid chromatography. The application of LC methods to drug analysis introduces a powerful tool for therapeutic drug monitoring as well as for clinical research. The advantages of short turnaround time, method reliability, method sensitivity, and drug specificity justify the use of LC techniques for various groups of the drug active compounds. This review describes some of the principles of ultra high performance liquid chromatography and high performance liquid chromatography, validation of these methods, system suitability tests for the methods, and application of methods to pharmaceutical analysis in the last 3 years.
Introduction:
Management of osteoarticular infections combines surgical treatment with antibiotic therapy. For some teams the immediate postoperative regimen requires at least partly wide-spectrum probabilistic treatment while waiting for the microbiological results. This protocol exposes the patient to the selection of resistant bacteria and the hospital unit to a modification of its bacterial ecology. The objective of this study was to retrospectively describe the microbial epidemiology of the Traumatology and Orthopaedics Department of the Lille University Hospital over 10 years (2002-2011).
Materials and methods:
The bacterial species isolated in culture of osteoarticular samples were listed, after removing any duplicates. The antibiotics retained for follow-up were those used in treatment of these infections as well as those recognized as markers of resistance. For Gram-positive species, the antibiotics considered were methicillin, rifampicin, fluoroquinolones, glycopeptides, and linezolid; for the Gram-negative species, cefotaxime, cefepime, imipenem, and fluoroquinolones were considered.
Results:
Of the 5006 strains isolated between 2002 and 2011, Gram-positive cocci accounted for more than 71%; Staphylococcus aureus 27%, and coagulase-negative staphylococci (CoNS) 54%. Contrary to S. aureus, resistance to methicillin, fluoroquinolones, and teicoplanin significantly increased in CoNS, reaching 44%, 34%, and 22%, respectively, of the strains in 2011. The proportion of streptococcal and enterococcal infections remained stable, a mean 7.4% and 5.3%, respectively, per year. Enterobacteria (12.5% of the isolates) were producers of extended-spectrum beta-lactamase in 7.8% of the cases. Pseudomonas aeruginosa was involved in 3.6% of the infections, and 12% of the strains remained resistant to ceftazidime. Propionibacterium acnes accounted for 5.8% of the bacteria isolated and showed few antibiotic resistance problems.
Discussion:
Stability in the distribution and the susceptibility of different bacterial species was noted over this 10-year period. Although the evolution of S. aureus resistance was favourable, the resistance of CoNS specially to methicillin and glycopeptides increased.
Level of evidence:
Level IV. Retrospective cohort study.
Monitoring of plasma antibiotic concentrations is necessary for individualization of antimicrobial chemotherapy dosing in special patient populations. One of these special populations of interest are the post-bariatric surgery patients. Until today, little is known on the effect of this procedure on drug disposition and efficacy. Therefore, close monitoring of antimicrobial plasma concentrations in these patients is warranted. A fast and uniform ultra-high-performance liquid chromatography (UPLC) method with tandem mass spectrometric detection (MS/MS) has been developed and qualified for the simultaneous quantification of β-lactam antibiotics in human plasma. Compounds included in this multi-component analysis are: amoxicillin, ampicillin, phenoxymethylpenicillin, piperacillin, cefuroxime, cefadroxil, flucloxacillin, meropenem, cefepime, ceftazidime, tazobactam, linezolid and cefazolin. After spiking of five different stable isotope labelled internal standards, plasma samples were prepared for UPLC-MS/MS analysis by mixed-mode solid phase extraction. The developed method was proven to be free of (relative) matrix effects and proved to be reliable for the quantification of 12 out of 13 β-lactam antibiotics. As a proof of concept the method has been applied to plasma samples obtained from a healthy volunteer treated with amoxicillin. The analytical method is suitable for use in a therapeutic drug monitoring setting, providing the clinician with reliable measurements on β-lactam antibiotic plasma concentrations in a timely manner.
Objectives:
The %fT>MIC of ceftazidime has been shown to correlate with microbiological outcome of Gram-negative bacteria (GNB) in preclinical studies. However, clinical data are still lacking. We explored the relationship of ceftazidime exposure and outcome in patients with nosocomial pneumonia using data from a recent randomized, double-blind Phase 3 clinical trial.
Patients and methods:
Pharmacokinetic (PK) and demographic data from three clinical trials were used to construct a population PK model using non-linear mixed-effects modelling. Individual concentration-time curves and PK/pharmacodynamic indices were determined for individual patients. The MICs used in the analyses were the highest MICs for any GNB cultured at baseline or end of therapy.
Results:
A two-compartment model best fit the data, with creatinine clearance as covariate on clearance and age on the central compartment. Classification and regression tree analysis showed a breakpoint value of 44.9% (P<0.0001) for GNB in 154 patients. The Emax model showed a good fit (R(2) =0.93). The benefit of adequate treatment increased from an eradication rate of 0.4848 at %fT>MIC of 0% to 0.9971 at 100%. The EC50 was 46.8% and the EC90 was 95.5% for %fT>MIC. Exposure correlated significantly with both microbiological and clinical outcome at test-of-cure.
Conclusions:
We conclude that exposures to ceftazidime predict microbiological as well as clinical outcome, and the %fT>MIC required to result in a likely favourable outcome is >45% of the dosing interval. This value is similar to that observed in animal models and underscores the principle that adequate dosing can be predicted and is beneficial to patient care.
There is an increasing interest in monitoring plasma concentrations of β-lactam antibiotics. The objective of this work was to develop and validate a rapid ultra-performance liquid chromatographic method with tandem mass spectrometric detection (UPLC-MS/MS) for simultaneous quantification of amoxicillin, ampicillin, cefuroxime, cefazolin, ceftazidime, meropenem, piperacillin, clavulanic acid and tazobactam. Sample clean-up included protein precipitation with acetonitrile and back-extraction of acetonitrile with dichloromethane. Six deuterated β-lactam antibiotics were used as internal standards. Chromatographic separation was performed on a Waters ACQUITY UPLC system using a BEH C(18) column (1.7μm, 100mm×2.1mm) applying a binary gradient elution of water and acetonitrile both containing 0.1% formic acid. The total run time was 5.5min. The developed method was validated in terms of precision, accuracy, linearity, matrix effect and recovery. The assay has now been successfully used to determine concentrations of amoxicillin/clavulanic acid, cefuroxime and meropenem in plasma samples from intensive care patients.
Penicillins and cephalosporins belong to the most prescribed antibiotics. Despite the relatively extended knowledge of these drugs, the qualitative and quantitative analysis of the compounds still gives rise to many problems. These difficulties are due to the chemical instability of the common -lactam nucleus, the minor differences in chemical structures between the analogues, and the complex and relatively fast degradation of the compounds in aqueous solutions. In this review a compilation of the physicochemical properties, the degradation routes and methods for analysis of these substances in biological and other matrices is presented.
Optimizing the prescription of antimicrobials is required to improve clinical outcome from infections and to reduce the development of antimicrobial resistance. One such method to improve antimicrobial dosing in individual patients is through application of therapeutic drug monitoring (TDM). The aim of this manuscript is to review the place of TDM in the dosing of antimicrobial agents, specifically the importance of pharmacokinetics (PK) and pharmacodynamics (PD) to define the antimicrobial exposures necessary for maximizing killing or inhibition of bacterial growth. In this context, there are robust data for some antimicrobials, including the ratio of a PK parameter (e.g. peak concentration) to the minimal inhibitory concentration of the bacteria associated with maximal antimicrobial effect. Blood sampling of an individual patient can then further define the relevant PK parameter value in that patient and, if necessary, antimicrobial dosing can be adjusted to enable achievement of the target PK/PD ratio. To date, the clinical outcome benefits of a systematic TDM programme for antimicrobials have only been demonstrated for aminoglycosides, although the decreasing susceptibility of bacteria to available antimicrobials and the increasing costs of pharmaceuticals, as well as emerging data on pharmacokinetic variability, suggest that benefits are likely.
The extreme pharmacokinetic behaviour of drugs sometimes observed in critically ill patients poses a significant threat to the achievement of optimal antibiotic treatment outcomes. Scant information on beta-lactam antibiotic therapeutic drug monitoring (TDM) is available. The objective of this prospective study was to evaluate the practicality and utility of a beta-lactam TDM programme in critically ill patients. TDM was performed twice weekly on all eligible patients at a 30-bed tertiary referral critical care unit. Blood concentrations were determined by fast-throughput high-performance liquid chromatography (HPLC) assays and were available within 12h of sampling. Dose adjustment was instituted if the trough or steady-state blood concentration was below 4-5x the minimum inhibitory concentration (MIC) or above 10x MIC. A total of 236 patients were subject to TDM over an 11-month period. The mean+/-standard deviation age was 53.5+/-18.3 years. Dose adjustment was required in 175 (74.2%) of the patients, with 119 of these patients (50.4%) requiring dose increases after the first TDM. For outcome of therapy, 206 (87.3%) courses resulted in a positive treatment outcome and there were 30 (12.7%) treatment failures observed including 14 deaths and 15 courses requiring escalation to broader-spectrum agents; 1 course was ceased due to an adverse drug reaction. Using binomial logistic regression, only an elevated Acute Physiology and Chronic Health Evaluation (APACHE) II score (P<0.01) and elevated plasma creatinine concentration (P=0.05) were found to be predictive of mortality. In conclusion, further research is required to determine definitively whether achievement of optimal beta-lactam pharmacodynamic targets improves clinical outcomes.
A simple and economical high performance liquid chromatography method was developed and validated for routine analysis of 12 Penicillin, Cephalosporin and Carbapenem antibiotics in 200 microL of human plasma. Antibiotics determined were Ceftazidime, Meropenem, Ceftriaxone, Ampicillin, Cefazolin, Ertapenem, Cephalothin, Benzylpenicillin, Flucloxacillin, Dicloxacillin, Piperacillin and Ticarcillin. There was a common sample preparation approach involving precipitation of proteins with acetonitrile and removal of lipid-soluble components by a chloroform wash. Separations were performed on a Waters X-bridge C18 column with, depending on analytes, one of three acetonitrile-phosphate buffer mobile phases. Detection was by UV at 210, 260 and 304 nm. Validation has demonstrated the method to be linear, accurate and precise. The method has been used in a pathology laboratory for therapeutic drug monitoring (TDM) of beta-lactams in critically ill patients.
Ultra Performance Liquid Chromatography (UPLC) is a relatively new technique giving new possibilities in liquid chromatography, especially concerning decrease of time and solvent consumption. UPLC chromatographic system is designed in a special way to withstand high system back-pressures. Special analytical columns UPLC Acquity UPLC BEH C(18) packed with 1.7 microm particles are used in connection with this system. The quality control analyses of four pharmaceutical formulations were transferred from HPLC to UPLC system. The results are compared for Triamcinolon cream containing trimacinolone acetonide, methylparaben, propylparaben and triamcinolone as degradation product, for Hydrocortison cream (hydrocortisone acetate, methylparaben, propylparaben and hydrocortisone degradation product), for Indomethacin gel (indomethacin and its degradation products 4-chlorobenzoic acid and 5-methoxy-2-methylindoleacetic acid) and for Estrogel gel (estradiol, methylparaben, propylparaben and estrone as degradation product). The UPLC system allows shortening analysis time up to nine times comparing to the conventional system using 5 microm particle packed analytical columns. In comparison with 3 microm particle packed analytical columns analysis should be shortened about three times. The negative effect of particle decrease is back-pressure increase about nine times (versus 5 microm) or three times (versus 3 microm), respectively. The separation on UPLC is performed under very high pressures (up to 100MPa is possible in UPLC system), but it has no negative influence on analytical column or other components of chromatographic system. Separation efficiency remains maintained or is even improved. Differences and SST parameters, advantages and disadvantages of UPLC are discussed.
Penicillins and cephalosporins belong to the most prescribed antibiotics. Despite the relatively extended knowledge of these drugs, the qualitative and quantitative analysis of the compounds still gives rise to many problems. These difficulties are due to the chemical instability of the common beta-lactam nucleus, the minor differences in chemical structures between the analogues, and the complex and relatively fast degradation of the compounds in aqueous solutions. In this review a compilation of the physicochemical properties, the degradation routes and methods for analysis of these substances in biological and other matrices is presented.
First-order rate constants (k) were determined for the hydrolysis of ceftazidime in the pH range of 0.5 to 8.5 at 45, 55, and 65 degrees C by a stability-indicating HPLC assay. In the absence of buffer effects, the pH-rate expression was k = kH1f1(aH+) + kH2f2(aH+) + kH3f3(aH+) + kSf3 + kOHf3(aOH-), where KH and KOH are the catalytic rate constants for the activity of hydrogen (aH+) and hydroxyl (aOH-) ions, respectively, and kS is the rate constant for spontaneous hydrolysis. The fractions of ceftazidime in various stages of dissociation (f1, f2, and f3) were calculated from kinetically determined apparent Ka values of 2.03 x 10(-2) and 4.85 x 10(-5). Catalytic constants (kcat) were calculated for formate, acetate, phosphate, and borate buffers, which accelerated hydrolysis. Each of the rate constants (kH1, kH2, kH3, kS, kOH, and kcat) were described as a function of temperature with calculated A and E values in the Arrhenius equation, kT = Ae-E/RT. Ceftazidime hydrolysis rate constants (k) were calculated as a function of pH, temperature, and buffer by combining the pH-rate expression with the buffer contributions calculated from kcat values and the temperature dependencies. These equations and their parameter values successfully calculated 95 of 104 experimentally determined rate constants with errors of < 10%. Maximum stability was observed in the relatively pH-independent region from 4.5 to 6.5. Hydrolysis rate constants at 30 degrees C were predicted and experimentally verified for four ceftazidime solutions, three of which (pH 4.4 acetate buffer and pH 5.5 and 6.5 phosphate buffers) maintained 90% of their initial concentration for approximately 1.5 days.
Ceftazidime is a third generation cephalosporin antibacterial agent which, since its introduction in the early 1980s, has retained a broad spectrum of in vitro antimicrobial activity and clinical utility in serious infections. However, increasing resistance to ceftazidime and other third generation cephalosporins, particularly among Enterobacteriaceae, due to the emergence of plasmid-mediated extended spectrum beta-lactamases and the class I chromosomally mediated beta-lactamases, is of concern. There is now a wealth of information on the pharmacokinetics of the drug. enabling ceftazidime to be used predictably, and with a low potential for adverse effects, in a diversity of patient populations. Overall, ceftazidime remains an effective agent for the treatment of serious infection, particularly those due to major nosocomial pathogens, and respiratory infections in patients with cystic fibrosis. Ceftazidime-containing regimens also remain an important option for the empirical therapy of febrile episodes in neutropenic patients. The tolerability profile of ceftazidime makes the drug a useful option in seriously ill patients who are at risk of developing adverse events with other antibacterial agents. Although patterns of bacterial resistance have changed in the ensuing years since its introduction, judicious use of this important agent will help maintain its present clinical utility.
A sensitive and rapid HPLC assay for the determination of the beta-lactam antibiotics ceftazidime and meropenem in serum and bronchial secretions is described. HPLC-integrated sample preparation allows direct injection of serum samples without any pretreatment. Sputum samples need only a simple homogenisation and volume measurement but no liquefying reagents are necessary. The inline extraction technique is realized by automatically switching from the extraction column to the analytical column. After the matrix passed the extraction column, the retained analyte is quantitatively transferred to the analytical column where separation by isocratic HPLC is performed. Ceftazidime and meropenem are detected according to their absorption maxima at 258 and 296 nm, respectively. The detection limit of both antibiotics is estimated to be better than 0.5 microg/ml in serum as well as in sputum samples. The described procedure allows determination of the antibiotics within 30-45 min, thereby facilitating drug monitoring in clinical routine.
Recent technological advances have made available reverse phase chromatographic media with a 1.7 microm particle size along with a liquid handling system that can operate such columns at much higher pressures. This technology, termed ultra performance liquid chromatography (UPLC), offers significant theoretical advantages in resolution, speed, and sensitivity for analytical determinations, particularly when coupled with mass spectrometers capable of high-speed acquisitions. This paper explores the differences in LC-MS performance by conducting a side-by-side comparison of UPLC for several methods previously optimized for HPLC-based separation and quantification of multiple analytes with maximum throughput. In general, UPLC produced significant improvements in method sensitivity, speed, and resolution. Sensitivity increases with UPLC, which were found to be analyte-dependent, were as large as 10-fold and improvements in method speed were as large as 5-fold under conditions of comparable peak separations. Improvements in chromatographic resolution with UPLC were apparent from generally narrower peak widths and from a separation of diastereomers not possible using HPLC. Overall, the improvements in LC-MS method sensitivity, speed, and resolution provided by UPLC show that further advances can be made in analytical methodology to add significant value to hypothesis-driven research.
The Third AAPS/FDA Bioanalytical Workshop, entitled "Quantitative Bioanalytical Methods Validation and Implementation: Best Practices for Chromatographic and Ligand Binding Assays" was held on May 1-3, 2006 in Arlington, VA. The format of this workshop consisted of presentations on bioanalytical topics, followed by discussion sessions where these topics could be debated, with the goal of reaching consensus, or identifying subjects where addition input or clarification was required. The discussion also addressed bioanalytical validation requirements of regulatory agencies, with the purpose of clarifying expectations for regulatory submissions. The proceedings from each day were reviewed and summarized in the evening sessions among the speakers and moderators of the day. The consensus summary was presented back to the workshop on the last day and was further debated. This communication represents the distillate of the workshop proceedings and provides the summary of consensus reached and also contains the validation topics where no consensus was reached.
Monitoring of plasma antibiotic drugs is useful for better clinical management in infected patients, particularly in intensive care units. A simple and sensitive high-performance liquid chromatography (HPLC) method with ultraviolet (UV) detection has been developed and validated for simultaneous quantification of five beta-lactam antibiotics in human plasma: cefepim, ceftazidim, cefuroxim, meropenem and piperacillin. The plasma sample, after spiked with ceforanid as an internal standard (IS), was submitted to a solid-phase extraction (SPE) prior to HPLC analysis. A chromatographic separation was achieved on a C8 symmetry column with a mobile phase consisting of an acetonitrile and phosphate buffer (pH 7.4) mixture in a gradient mode. Detection was carried out at a wavelength between 200 and 400 nm. The method developed was linear over the concentration range of 2.5-60 microg/mL for each antibiotic in the plasma samples. Accuracy ranged from 93.2 to 107.1% and precision was between 0.9 and 12.2%. The method has been applied to plasma samples obtained from patients treated with beta-lactam antibiotics and is appropriated for easy determination of plasma concentrations for therapeutic monitoring applications.
The objective of this study was to evaluate the relationship of the predicted pharmacodynamic parameters 24-h area under the inhibitory curve (AUIC=area under the concentration-time curve for 24h of dosing/minimum inhibitory concentration (AUC0-24/MIC) and time above the minimum inhibitory concentration (T>MIC) with clinical and microbiological outcomes in patients with bacteraemia and sepsis treated with cefepime or ceftazidime. Pharmacokinetic and pharmacodynamic parameters were derived for 76 of 107 patients enrolled in two prospective, randomised, clinical trials comparing cefepime with ceftazidime for the treatment of sepsis with bacteraemia, lower respiratory tract infection or complicated urinary tract infection. The relationships between the pharmacodynamic parameters and outcomes were examined. Whilst no significant differences in clinical outcomes were observed between cefepime and ceftazidime, there were significant differences in the pharmacodynamic analysis. Patients with an AUIC> or =250 had significantly greater clinical cure (79% vs. 33%; P=0.002) and bacteriological eradication (96% vs. 44%; P<0.001) than patients with an AUIC<250. Patients with T>MIC of 100% had significantly greater clinical cure (82% vs. 33%; P=0.002) and bacteriological eradication (97% vs. 44%; P<0.001) than patients with T>MIC of <100%. Both microbiological and clinical cure rates were suboptimal in patients receiving cefepime or ceftazidime for the treatment of serious infections if the AUIC was <250 or T>MIC was <100%.
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