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Etienne Chatelut - One of the best experts on this subject based on the ideXlab platform.
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determination of dolutegravir s Unbound Fraction in human plasma using validated equilibrium dialysis and lc ms ms methods
Clinica Chimica Acta, 2018Co-Authors: David Metsu, Etienne Chatelut, François Fraissinet, Didier Concordet, Thomas Lanot, Melanie Picot, Marion Cabrol, Frederique Duboisgalopin, Pierre Delobel, Peggy GandiaAbstract:Abstract Assessment of the Unbound pharmacologically active Fraction (fu; as the ratio of Unbound to total concentration) of dolutegravir could improve therapeutic drug monitoring (TDM) in patients that experience virological failure or toxicity, despite receiving adequate total concentrations. This study evaluated (i) dolutegravir's fu through equilibrium dialysis (ED), (ii) the pre-analytical parameters that influence fu, and (iii) fu's inter-individual variability in HIV patients. Validation of the LC-MS/MS method followed FDA guidelines. The results, based on coefficients of variation (results from nominal concentrations
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Quinine Unbound concentration is the best marker for therapeutic drug monitoring
Therapie, 2016Co-Authors: Carlos De Pablos-martinez, Etienne Chatelut, Lydie Porte, François Fraissinet, Antoine Berry, Patrick Seraissol, Michel Lavit, Didier Concordet, Peggy GandiaAbstract:Quinine monitoring should be based on Unbound concentration due to variable Unbound Fraction in malaria patients.
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determination of Unbound Fraction of pazopanib in vitro and in cancer patients reveals albumin as the main binding site
Investigational New Drugs, 2016Co-Authors: Dianecharlotte Imbs, Marienoelle Paludetto, S Negrier, Helen Powell, Thierry Lafont, Melanie Whitekoning, Etienne Chatelut, Fabienne ThomasAbstract:Introduction Pazopanib exhibits wide inter-patient pharmacokinetic variability which may contribute to differences in treatment outcome. Unbound drug concentrations are believed to be more relevant to pharmacological responses than total concentrations. Thus it is desirable to evaluate pazopanib binding on plasma proteins and different factors potentially affecting this process. Methods An equilibrium dialysis method coupled with UPLC-MS/MS assay has been optimized and validated for the determination of pazopanib Unbound Fraction (fu%) in human plasma. Pazopanib binding in the plasma of healthy volunteers and in isolated protein solutions was investigated. The Unbound Fraction was determined for 24 cancer patients treated daily with pazopanib. Results We found that pazopanib was extensively bound in human plasma (>99.9 %) with a mean fu% value of 0.0106 ± 0.0013 % at 40 μg/mL. Protein binding was concentration independent over a clinically relevant range of concentrations. In isolated protein solutions, pazopanib at 40 μg/mL was mainly bound to albumin (40 g/L) and to a lesser extent to α1-acid glycoprotein (1 g/L) and low density lipoproteins (1.2 g/L), with a mean fu% of 0.0073 ± 0.0022 %, 0.992 ± 0.44 % and 7.4 ± 1.7 % respectively. Inter-patient variability (CV%) of fu% in cancer patients was limited (27.2 %). A correlation was observed between individual Unbound Fraction values and albuminemia. Conclusions Pazopanib exhibits extensive binding to plasma proteins in human plasma. Variable albumin concentrations, frequently observed in cancer patients, may affect pazopanib Unbound Fraction with implications for inter-patient variability in drug efficacy and toxicity.
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determination of plasma Unbound Fraction of voriconazole in patients treated with a prophylactic or a curative treatment
Therapeutic Drug Monitoring, 2014Co-Authors: Aurelie Florent, Etienne Chatelut, Peggy Gandia, Patrick Seraissol, G HouinAbstract:BACKGROUND: Voriconazole (VOR) is a triazole antifungal used in the curative treatment of invasive fungal infections and the prophylactic treatment of opportunistic fungal infections in immunocompromised patients. It is a drug for which therapeutic drug monitoring (TDM) is highly recommended. METHODS: To determine the best TDM marker, the pharmacologically active form of the drug, represented by the plasma Unbound concentration (Cu) and Fraction (fu), has been studied using a method based on ultrafiltration and ultra performance liquid chromatography. As albumin (Alb) is a likely factor inducing fluctuations in fu, the correlation between Alb levels and fu was carried out. Similarly, correlations between trough plasma concentrations [total concentration (Ct) and Cu] and both efficacy and safety markers were determined. Efficacy evaluation was based on monitoring fungal antigens and cultures, whereas safety was monitored by measuring bilirubin levels. RESULTS: In vitro, using blank human plasma, the mean fu was determined at 32.3% ± 5.5%, whereas in patients' plasmas treated with VOR, the median (5th-95th percentiles) of the Unbound VOR Fraction was 22.95% (14.95%-38.42%). A high correlation was found (rho = 0.956, P < 0.001) between Ct and Cu, though there was no correlation between serum Alb levels and fu, except for some patients with severe hypoalbuminemia (<25 g/L). CONCLUSIONS: Based on the efficacy/safety correlations, a therapeutic window has been defined ranging from 4.5 to 6.5 mg/L and 1.5 and 2.0 mg/L for trough Ct and Cu, respectively. For the first time, the relevance of new pharmacokinetic parameters, such as Cu and fu, has been explored and discussed, and our results support the current TDM protocol for VOR.
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should therapeutic drug monitoring of the Unbound Fraction of imatinib and its main active metabolite n desmethyl imatinib be developed
Cancer Chemotherapy and Pharmacology, 2013Co-Authors: Peggy Gandia, Thierry Lafont, Cecile Arellano, Francoise Huguet, Laurence Malard, Etienne ChatelutAbstract:Purpose The European Society for Medical Oncology recommends therapeutic drug monitoring (TDM) for imatinib, based on total plasma concentrations in cases of sub-optimal response, failure, or adverse events. Imatinib is highly bound to alpha-1 acid glycoprotein (AGP) in the plasma. We determined the Unbound plasma Fraction of both imatinib and its main active metabolite (N-desmethylimatinib) in plasma from 44 patients. The objective was to quantify the inter-individual variability of the protein binding of imatinib in order to discuss the potential benefits and limits of TDM of free plasma concentrations. Patients and methods The quantification of Unbound Fraction of imatinib and N-desmethyl-imatinib was performed using plasma ultrafiltration coupled with LC‐MS/ MS measurement. 60 pre-dose plasma samples were obtained at steady state within TDM in 44 chronic myeloid leukemia patients. Results The mean Unbound Fractions of imatinib and N-desmethyl-imatinib were 2.94 and 5.10 %, respectively, with inter-individual variability (CV in %) of 57 % for imatinib and 71 % for the metabolite. For 11 patients, repeated blood sampling gave a mean intra-individual variability of 28 % for imatinib and 34 % for N-desmethylimatinib. No correlation was observed between these measured individual imatinib Unbound Fraction values and those obtained using an equation based on AGP levels previously proposed by Widmer et al. The mean N-desmethyl-imatinib/imatinib ratio was determined for both total (0.69) and Unbound (1.10) concentrations, with interindividual variabilities of 71 and 86 %, respectively. Conclusion The large inter-individual variability for the Unbound Fraction of both imatinib and N-desmethyl-imatinib warrants further evaluation of the pharmacokinetic‐pharmacodynamic relationship as a potential relevant marker of imatinib therapeutic outcomes.
Peggy Gandia - One of the best experts on this subject based on the ideXlab platform.
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determination of dolutegravir s Unbound Fraction in human plasma using validated equilibrium dialysis and lc ms ms methods
Clinica Chimica Acta, 2018Co-Authors: David Metsu, Etienne Chatelut, François Fraissinet, Didier Concordet, Thomas Lanot, Melanie Picot, Marion Cabrol, Frederique Duboisgalopin, Pierre Delobel, Peggy GandiaAbstract:Abstract Assessment of the Unbound pharmacologically active Fraction (fu; as the ratio of Unbound to total concentration) of dolutegravir could improve therapeutic drug monitoring (TDM) in patients that experience virological failure or toxicity, despite receiving adequate total concentrations. This study evaluated (i) dolutegravir's fu through equilibrium dialysis (ED), (ii) the pre-analytical parameters that influence fu, and (iii) fu's inter-individual variability in HIV patients. Validation of the LC-MS/MS method followed FDA guidelines. The results, based on coefficients of variation (results from nominal concentrations
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Quinine Unbound concentration is the best marker for therapeutic drug monitoring
Therapie, 2016Co-Authors: Carlos De Pablos-martinez, Etienne Chatelut, Lydie Porte, François Fraissinet, Antoine Berry, Patrick Seraissol, Michel Lavit, Didier Concordet, Peggy GandiaAbstract:Quinine monitoring should be based on Unbound concentration due to variable Unbound Fraction in malaria patients.
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determination of plasma Unbound Fraction of voriconazole in patients treated with a prophylactic or a curative treatment
Therapeutic Drug Monitoring, 2014Co-Authors: Aurelie Florent, Etienne Chatelut, Peggy Gandia, Patrick Seraissol, G HouinAbstract:BACKGROUND: Voriconazole (VOR) is a triazole antifungal used in the curative treatment of invasive fungal infections and the prophylactic treatment of opportunistic fungal infections in immunocompromised patients. It is a drug for which therapeutic drug monitoring (TDM) is highly recommended. METHODS: To determine the best TDM marker, the pharmacologically active form of the drug, represented by the plasma Unbound concentration (Cu) and Fraction (fu), has been studied using a method based on ultrafiltration and ultra performance liquid chromatography. As albumin (Alb) is a likely factor inducing fluctuations in fu, the correlation between Alb levels and fu was carried out. Similarly, correlations between trough plasma concentrations [total concentration (Ct) and Cu] and both efficacy and safety markers were determined. Efficacy evaluation was based on monitoring fungal antigens and cultures, whereas safety was monitored by measuring bilirubin levels. RESULTS: In vitro, using blank human plasma, the mean fu was determined at 32.3% ± 5.5%, whereas in patients' plasmas treated with VOR, the median (5th-95th percentiles) of the Unbound VOR Fraction was 22.95% (14.95%-38.42%). A high correlation was found (rho = 0.956, P < 0.001) between Ct and Cu, though there was no correlation between serum Alb levels and fu, except for some patients with severe hypoalbuminemia (<25 g/L). CONCLUSIONS: Based on the efficacy/safety correlations, a therapeutic window has been defined ranging from 4.5 to 6.5 mg/L and 1.5 and 2.0 mg/L for trough Ct and Cu, respectively. For the first time, the relevance of new pharmacokinetic parameters, such as Cu and fu, has been explored and discussed, and our results support the current TDM protocol for VOR.
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should therapeutic drug monitoring of the Unbound Fraction of imatinib and its main active metabolite n desmethyl imatinib be developed
Cancer Chemotherapy and Pharmacology, 2013Co-Authors: Peggy Gandia, Thierry Lafont, Cecile Arellano, Francoise Huguet, Laurence Malard, Etienne ChatelutAbstract:Purpose The European Society for Medical Oncology recommends therapeutic drug monitoring (TDM) for imatinib, based on total plasma concentrations in cases of sub-optimal response, failure, or adverse events. Imatinib is highly bound to alpha-1 acid glycoprotein (AGP) in the plasma. We determined the Unbound plasma Fraction of both imatinib and its main active metabolite (N-desmethylimatinib) in plasma from 44 patients. The objective was to quantify the inter-individual variability of the protein binding of imatinib in order to discuss the potential benefits and limits of TDM of free plasma concentrations. Patients and methods The quantification of Unbound Fraction of imatinib and N-desmethyl-imatinib was performed using plasma ultrafiltration coupled with LC‐MS/ MS measurement. 60 pre-dose plasma samples were obtained at steady state within TDM in 44 chronic myeloid leukemia patients. Results The mean Unbound Fractions of imatinib and N-desmethyl-imatinib were 2.94 and 5.10 %, respectively, with inter-individual variability (CV in %) of 57 % for imatinib and 71 % for the metabolite. For 11 patients, repeated blood sampling gave a mean intra-individual variability of 28 % for imatinib and 34 % for N-desmethylimatinib. No correlation was observed between these measured individual imatinib Unbound Fraction values and those obtained using an equation based on AGP levels previously proposed by Widmer et al. The mean N-desmethyl-imatinib/imatinib ratio was determined for both total (0.69) and Unbound (1.10) concentrations, with interindividual variabilities of 71 and 86 %, respectively. Conclusion The large inter-individual variability for the Unbound Fraction of both imatinib and N-desmethyl-imatinib warrants further evaluation of the pharmacokinetic‐pharmacodynamic relationship as a potential relevant marker of imatinib therapeutic outcomes.
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determination of Unbound Fraction of imatinib and n desmethyl imatinib validation of an uplc ms ms assay and ultrafiltration method
Analytical Abstracts, 2012Co-Authors: Cecile Arellano, Thierry Lafont, Peggy Gandia, Rutchanna Jongejan, Etienne ChatelutAbstract:Imatinib is a small-molecule tyrosine kinase inhibitor with large inter-individual but low intra-individual pharmacokinetic variability with consistent concentration-efficacy and concentration-toxicity relationships. For these reasons imatinib therapeutic drug monitoring is based on total plasma concentrations. However, since a significant impact of Unbound imatinib concentrations on clinical response and/or toxicity evaluation has been suggested, the quantification of free Fraction of imatinib and its active metabolite are of interest for therapeutic monitoring. Hence a reliable method for both separation and assay of the free Fraction is needed. Using plasma samples spiked with imatinib (from 1000 to 7500 ng/mL) and its metabolite (from 1000 to 2500 ng/mL), an ultrafiltration procedure and an UPLC assay which give reproductive values for Unbound Fractions of imatinib (mean 3.0 ± 1.0%) and metabolite N-desmethyl imatinib (3.6 ± 1.8%) have been developed. The validation of the analytical UPLC-MS/MS method associated to ultrafiltration for quantification of imatinib and N-desmethyl imatinib was reported. The LOQ was set at 10 ng/mL for imatinib and 20 ng/mL for N-desmethyl imatinib, intraday CV (%) ranged from 2.7 to 4.8% for imatinib and from 5.4 to 12.4% for N-desmethyl imatinib and interday CV (%) ranged from 5.6 to 6.5% for imatinib and from 5.4 to 16.1% for N-desmethyl imatinib. Methodological modifications were attempted to overcome non specific binding (NSB) on the ultrafiltration device. Two types of devices previously used for Unbound determination of drugs were tested. Our results clearly showed that the methodology and the features of devices used for ultrafiltration could totally compromise the determination of Unbound concentrations of a drug.
Martin G Kees - One of the best experts on this subject based on the ideXlab platform.
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Impact of Experimental Variables on the Protein Binding of Tigecycline in Human Plasma as Determined by Ultrafiltration
Journal of Pharmaceutical Sciences, 2017Co-Authors: Christoph Dorn, Frieder Kees, Alexander Kratzer, Uwe Liebchen, Michael Schleibinger, Alexandra Murschhauser, Jens Schlossmann, Philipp Simon, Martin G KeesAbstract:Abstract Tigecycline, a tetracycline derivative, shows atypical plasma protein binding behavior. The Unbound Fraction decreases with increasing concentration at therapeutic concentrations. Moreover, uncertainty exists about the magnitude of tigecyline's protein binding in man. Unbound Fractions between 2.5% and 35% have been reported in plasma from healthy volunteers, and between 25% and 100% in patients, respectively. In the present study, the protein binding of tigecycline has been investigated by ultrafiltration using different experimental conditions. Whereas temperature had only a marginal influence, the Unbound Fraction at 0.3/3.0 mg/L was low at pH 8.2 (9.4%/1.9%) or in unbuffered pooled plasma (6.3%/1.2%), compared with plasma buffered with HEPES to pH 7.4 (65.9%/39.7%). In experiments with phosphate buffer and EDTA, the concentration dependency was markedly attenuated or abolished, which is compatible with a cooperative binding mechanism involving divalent cations such as calcium. The Unbound Fraction in clinical plasma samples from patients treated with tigecycline was determined to 66.3 ± 13.7% at concentrations 1 to
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Unbound Fraction of ertapenem in intensive care unit patients
Journal of Antimicrobial Chemotherapy, 2014Co-Authors: Uwe Liebchen, Martin G Kees, Sebastian G Wicha, Frieder Kees, Charlotte Kloft, Alexander KratzerAbstract:Patients and methods:For assessing the influence of experimental conditions and for development of the ultrafiltration protocol, plasma from healthy volunteers was used. Concentrations of total and Unbound ertapenem were determined by HPLC in 29 plasma samples from six ICU patients treated with 1 g of ertapenem once daily. The concentration‐time courses were described by a one-compartment model. Ertapenem binding to albumin was assessed byMichaelis‐Menten kinetics in solutions of human serum albumin, in plasmafrom healthy volunteers and in plasma from ICU patients. Results:The Unbound Fraction (f u ) of ertapenem was highly susceptible to pH and temperature during ultrafiltration and was!20% in plasma from healthy volunteers at clinically relevant concentrations. In ICU patients, f u was substantially higher (range 30.9%‐53.6%). The Unbound concentrations of ertapenem exceeded 2 mg/L for 72% (median; range 39%‐100%) of the 24 h dosing interval and 0.25 mg/L for 100% (range 79%‐100%). The numberof bindingsites peralbuminmoleculewas1.22(95%CI1.07‐1.38) inplasmafrom healthy volunteers and 0.404 (95% CI 0.158‐0.650) in samples from ICU patients. Conclusions:Determination of Unbound ertapenem by ultrafiltration is susceptible to experimental conditions. When determined at physiological pH and temperature, f u of ertapenem is 2- to 4-fold higher than previously reported and even higher in ICU patients. Binding studies indicate that hypoalbuminaemia alone does not explain these differences. This issue should be further investigated for its clinical relevance.
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Unbound Fraction of vancomycin in intensive care unit patients
The Journal of Clinical Pharmacology, 2014Co-Authors: Martin G Kees, Sebastian G Wicha, Astrid Seefeld, Frieder Kees, Charlotte KloftAbstract:Published data on the Unbound Fraction of vancomycin in patient samples exhibit high variability. In the present study, a robust ultrafiltration method was developed and applied to 102 clinical samples from 22 intensive care unit patients who were treated with continuous infusion of vancomycin. A validated HPLC method was used for determination of total and Unbound concentrations. The mean Unbound Fraction was 67.2% (standard deviation 7.5%, range 47.2–92.1%) and independent of total concentration of vancomycin or of albumin. The Unbound Fraction was significantly correlated (r = +0.67, P = .0009) with the renally filtered Fraction (drug clearance/creatinine clearance), providing functional evidence for the validity of the measurements. Ultrafiltration proved to be susceptible to variations in the experimental conditions such as pH, temperature and centrifugal force. The measured Unbound Fraction increased from 60% at pH 6 to 100% at pH 9, from 57% at 4°C to 80% at 37°C, and was 76% at 1,000 g compared with 45% at 10,000 g. Lack of standardization may therefore partly explain the variable results reported in the literature.
Thierry Lafont - One of the best experts on this subject based on the ideXlab platform.
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determination of Unbound Fraction of pazopanib in vitro and in cancer patients reveals albumin as the main binding site
Investigational New Drugs, 2016Co-Authors: Dianecharlotte Imbs, Marienoelle Paludetto, S Negrier, Helen Powell, Thierry Lafont, Melanie Whitekoning, Etienne Chatelut, Fabienne ThomasAbstract:Introduction Pazopanib exhibits wide inter-patient pharmacokinetic variability which may contribute to differences in treatment outcome. Unbound drug concentrations are believed to be more relevant to pharmacological responses than total concentrations. Thus it is desirable to evaluate pazopanib binding on plasma proteins and different factors potentially affecting this process. Methods An equilibrium dialysis method coupled with UPLC-MS/MS assay has been optimized and validated for the determination of pazopanib Unbound Fraction (fu%) in human plasma. Pazopanib binding in the plasma of healthy volunteers and in isolated protein solutions was investigated. The Unbound Fraction was determined for 24 cancer patients treated daily with pazopanib. Results We found that pazopanib was extensively bound in human plasma (>99.9 %) with a mean fu% value of 0.0106 ± 0.0013 % at 40 μg/mL. Protein binding was concentration independent over a clinically relevant range of concentrations. In isolated protein solutions, pazopanib at 40 μg/mL was mainly bound to albumin (40 g/L) and to a lesser extent to α1-acid glycoprotein (1 g/L) and low density lipoproteins (1.2 g/L), with a mean fu% of 0.0073 ± 0.0022 %, 0.992 ± 0.44 % and 7.4 ± 1.7 % respectively. Inter-patient variability (CV%) of fu% in cancer patients was limited (27.2 %). A correlation was observed between individual Unbound Fraction values and albuminemia. Conclusions Pazopanib exhibits extensive binding to plasma proteins in human plasma. Variable albumin concentrations, frequently observed in cancer patients, may affect pazopanib Unbound Fraction with implications for inter-patient variability in drug efficacy and toxicity.
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should therapeutic drug monitoring of the Unbound Fraction of imatinib and its main active metabolite n desmethyl imatinib be developed
Cancer Chemotherapy and Pharmacology, 2013Co-Authors: Peggy Gandia, Thierry Lafont, Cecile Arellano, Francoise Huguet, Laurence Malard, Etienne ChatelutAbstract:Purpose The European Society for Medical Oncology recommends therapeutic drug monitoring (TDM) for imatinib, based on total plasma concentrations in cases of sub-optimal response, failure, or adverse events. Imatinib is highly bound to alpha-1 acid glycoprotein (AGP) in the plasma. We determined the Unbound plasma Fraction of both imatinib and its main active metabolite (N-desmethylimatinib) in plasma from 44 patients. The objective was to quantify the inter-individual variability of the protein binding of imatinib in order to discuss the potential benefits and limits of TDM of free plasma concentrations. Patients and methods The quantification of Unbound Fraction of imatinib and N-desmethyl-imatinib was performed using plasma ultrafiltration coupled with LC‐MS/ MS measurement. 60 pre-dose plasma samples were obtained at steady state within TDM in 44 chronic myeloid leukemia patients. Results The mean Unbound Fractions of imatinib and N-desmethyl-imatinib were 2.94 and 5.10 %, respectively, with inter-individual variability (CV in %) of 57 % for imatinib and 71 % for the metabolite. For 11 patients, repeated blood sampling gave a mean intra-individual variability of 28 % for imatinib and 34 % for N-desmethylimatinib. No correlation was observed between these measured individual imatinib Unbound Fraction values and those obtained using an equation based on AGP levels previously proposed by Widmer et al. The mean N-desmethyl-imatinib/imatinib ratio was determined for both total (0.69) and Unbound (1.10) concentrations, with interindividual variabilities of 71 and 86 %, respectively. Conclusion The large inter-individual variability for the Unbound Fraction of both imatinib and N-desmethyl-imatinib warrants further evaluation of the pharmacokinetic‐pharmacodynamic relationship as a potential relevant marker of imatinib therapeutic outcomes.
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determination of Unbound Fraction of imatinib and n desmethyl imatinib validation of an uplc ms ms assay and ultrafiltration method
Analytical Abstracts, 2012Co-Authors: Cecile Arellano, Thierry Lafont, Peggy Gandia, Rutchanna Jongejan, Etienne ChatelutAbstract:Imatinib is a small-molecule tyrosine kinase inhibitor with large inter-individual but low intra-individual pharmacokinetic variability with consistent concentration-efficacy and concentration-toxicity relationships. For these reasons imatinib therapeutic drug monitoring is based on total plasma concentrations. However, since a significant impact of Unbound imatinib concentrations on clinical response and/or toxicity evaluation has been suggested, the quantification of free Fraction of imatinib and its active metabolite are of interest for therapeutic monitoring. Hence a reliable method for both separation and assay of the free Fraction is needed. Using plasma samples spiked with imatinib (from 1000 to 7500 ng/mL) and its metabolite (from 1000 to 2500 ng/mL), an ultrafiltration procedure and an UPLC assay which give reproductive values for Unbound Fractions of imatinib (mean 3.0 ± 1.0%) and metabolite N-desmethyl imatinib (3.6 ± 1.8%) have been developed. The validation of the analytical UPLC-MS/MS method associated to ultrafiltration for quantification of imatinib and N-desmethyl imatinib was reported. The LOQ was set at 10 ng/mL for imatinib and 20 ng/mL for N-desmethyl imatinib, intraday CV (%) ranged from 2.7 to 4.8% for imatinib and from 5.4 to 12.4% for N-desmethyl imatinib and interday CV (%) ranged from 5.6 to 6.5% for imatinib and from 5.4 to 16.1% for N-desmethyl imatinib. Methodological modifications were attempted to overcome non specific binding (NSB) on the ultrafiltration device. Two types of devices previously used for Unbound determination of drugs were tested. Our results clearly showed that the methodology and the features of devices used for ultrafiltration could totally compromise the determination of Unbound concentrations of a drug.
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Determination of Unbound Fraction of imatinib and N-desmethyl imatinib, validation of an UPLC–MS/MS assay and ultrafiltration method
Journal of Chromatography B, 2012Co-Authors: Cecile Arellano, Thierry Lafont, Peggy Gandia, Rutchanna Jongejan, Etienne ChatelutAbstract:Abstract Imatinib is a small-molecule tyrosine kinase inhibitor with large inter-individual but low intra-individual pharmacokinetic variability with consistent concentration–efficacy and concentration–toxicity relationships. For these reasons imatinib therapeutic drug monitoring is based on total plasma concentrations. However, since a significant impact of Unbound imatinib concentrations on clinical response and/or toxicity evaluation has been suggested, the quantification of free Fraction of imatinib and its active metabolite are of interest for therapeutic monitoring. Hence a reliable method for both separation and assay of the free Fraction is needed. Using plasma samples spiked with imatinib (from 1000 to 7500 ng/mL) and its metabolite (from 1000 to 2500 ng/mL), an ultrafiltration procedure and an UPLC assay which give reproductive values for Unbound Fractions of imatinib (mean 3.0 ± 1.0%) and metabolite N-desmethyl imatinib (3.6 ± 1.8%) have been developed. The validation of the analytical UPLC–MS/MS method associated to ultrafiltration for quantification of imatinib and N-desmethyl imatinib was reported. The LOQ was set at 10 ng/mL for imatinib and 20 ng/mL for N-desmethyl imatinib, intraday CV (%) ranged from 2.7 to 4.8% for imatinib and from 5.4 to 12.4% for N-desmethyl imatinib and interday CV (%) ranged from 5.6 to 6.5% for imatinib and from 5.4 to 16.1% for N-desmethyl imatinib. Methodological modifications were attempted to overcome non specific binding (NSB) on the ultrafiltration device. Two types of devices previously used for Unbound determination of drugs were tested. Our results clearly showed that the methodology and the features of devices used for ultrafiltration could totally compromise the determination of Unbound concentrations of a drug.
Charlotte Kloft - One of the best experts on this subject based on the ideXlab platform.
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Unbound Fraction of ertapenem in intensive care unit patients
Journal of Antimicrobial Chemotherapy, 2014Co-Authors: Uwe Liebchen, Martin G Kees, Sebastian G Wicha, Frieder Kees, Charlotte Kloft, Alexander KratzerAbstract:Patients and methods:For assessing the influence of experimental conditions and for development of the ultrafiltration protocol, plasma from healthy volunteers was used. Concentrations of total and Unbound ertapenem were determined by HPLC in 29 plasma samples from six ICU patients treated with 1 g of ertapenem once daily. The concentration‐time courses were described by a one-compartment model. Ertapenem binding to albumin was assessed byMichaelis‐Menten kinetics in solutions of human serum albumin, in plasmafrom healthy volunteers and in plasma from ICU patients. Results:The Unbound Fraction (f u ) of ertapenem was highly susceptible to pH and temperature during ultrafiltration and was!20% in plasma from healthy volunteers at clinically relevant concentrations. In ICU patients, f u was substantially higher (range 30.9%‐53.6%). The Unbound concentrations of ertapenem exceeded 2 mg/L for 72% (median; range 39%‐100%) of the 24 h dosing interval and 0.25 mg/L for 100% (range 79%‐100%). The numberof bindingsites peralbuminmoleculewas1.22(95%CI1.07‐1.38) inplasmafrom healthy volunteers and 0.404 (95% CI 0.158‐0.650) in samples from ICU patients. Conclusions:Determination of Unbound ertapenem by ultrafiltration is susceptible to experimental conditions. When determined at physiological pH and temperature, f u of ertapenem is 2- to 4-fold higher than previously reported and even higher in ICU patients. Binding studies indicate that hypoalbuminaemia alone does not explain these differences. This issue should be further investigated for its clinical relevance.
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Unbound Fraction of vancomycin in intensive care unit patients
The Journal of Clinical Pharmacology, 2014Co-Authors: Martin G Kees, Sebastian G Wicha, Astrid Seefeld, Frieder Kees, Charlotte KloftAbstract:Published data on the Unbound Fraction of vancomycin in patient samples exhibit high variability. In the present study, a robust ultrafiltration method was developed and applied to 102 clinical samples from 22 intensive care unit patients who were treated with continuous infusion of vancomycin. A validated HPLC method was used for determination of total and Unbound concentrations. The mean Unbound Fraction was 67.2% (standard deviation 7.5%, range 47.2–92.1%) and independent of total concentration of vancomycin or of albumin. The Unbound Fraction was significantly correlated (r = +0.67, P = .0009) with the renally filtered Fraction (drug clearance/creatinine clearance), providing functional evidence for the validity of the measurements. Ultrafiltration proved to be susceptible to variations in the experimental conditions such as pH, temperature and centrifugal force. The measured Unbound Fraction increased from 60% at pH 6 to 100% at pH 9, from 57% at 4°C to 80% at 37°C, and was 76% at 1,000 g compared with 45% at 10,000 g. Lack of standardization may therefore partly explain the variable results reported in the literature.
