title: High-throughput hydrophilic interaction chromatography coupled to tandem mass spectrometry for the optimized quantification of the anti-Gram-negatives antibiotic colistin A/B and its pro-drug colistimethate.
abstract: Colistin is a last resort's antibacterial treatment in critically ill patients with multi-drug resistant Gram-negative infections. As appropriate colistin exposure is the key for maximizing efficacy while minimizing toxicity, individualized dosing optimization guided by therapeutic drug monitoring is a top clinical priority. Objective of the present work was to develop a rapid and robust HPLC-MS/MS assay for quantification of colistin plasma concentrations. This novel methodology validated according to international standards simultaneously quantifies the microbiologically active compounds colistin A and B, plus the pro-drug colistin methanesulfonate (colistimethate, CMS). 96-well micro-Elution SPE on Oasis Hydrophilic-Lipophilic-Balanced (HLB) followed by direct analysis by Hydrophilic Interaction Liquid Chromatography (HILIC) with Ethylene Bridged Hybrid--BEH--Amide phase column coupled to tandem mass spectrometry allows a high-throughput with no significant matrix effect. The technique is highly sensitive (limit of quantification 0.014 and 0.006 μg/mL for colistin A and B), precise (intra-/inter-assay CV 0.6-8.4%) and accurate (intra-/inter-assay deviation from nominal concentrations -4.4 to +6.3%) over the clinically relevant analytical range 0.05-20 μg/mL. Colistin A and B in plasma and whole blood samples are reliably quantified over 48 h at room temperature and at +4°C (<6% deviation from nominal values) and after three freeze-thaw cycles. Colistimethate acidic hydrolysis (1M H2SO4) to colistin A and B in plasma was completed in vitro after 15 min of sonication while the pro-drug hydrolyzed spontaneously in plasma ex vivo after 4 h at room temperature: this information is of utmost importance for interpretation of analytical results. Quantification is precise and accurate when using serum, citrated or EDTA plasma as biological matrix, while use of heparin plasma is not appropriate. This new analytical technique providing optimized quantification in real-life conditions of the microbiologically active compounds colistin A and B offers a highly efficient tool for routine therapeutic drug monitoring aimed at individualizing drug dosing against life-threatening infections.
authors.affiliation: Division and Laboratory of Clinical Pharmacology, Service of Biomedicine, Department of Laboratories, Lausanne University Hospital (Centre Hospitalier Universitaire Vaudois, CHUV), Rue du Bugnon 46, CH-1011 Lausanne, Switzerland.
authors.forename: Thomas
authors.initials: T
authors.lastname: Mercier
authors.affiliation: Infectious Diseases Service, Department of Medicine, Lausanne University Hospital (Centre Hospitalier Universitaire Vaudois, CHUV), Lausanne, Switzerland.
authors.forename: Fréderic
authors.initials: F
authors.lastname: Tissot
authors.affiliation: Infectious Diseases Service, Department of Medicine, Lausanne University Hospital (Centre Hospitalier Universitaire Vaudois, CHUV), Lausanne, Switzerland.
authors.forename: Céline
authors.initials: C
authors.lastname: Gardiol
authors.affiliation: Department of Clinical Pharmacology and Toxicology, Zürich University Hospital (Universitätsspital Zürich, USZ), Zürich, Switzerland.
authors.forename: Natascia
authors.initials: N
authors.lastname: Corti
authors.affiliation: Nephrology Service, Department of Medicine, Cantonal Hospital, Winterthur, Switzerland.
authors.forename: Stéphane
authors.initials: S
authors.lastname: Wehrli
authors.affiliation: Division and Laboratory of Clinical Pharmacology, Service of Biomedicine, Department of Laboratories, Lausanne University Hospital (Centre Hospitalier Universitaire Vaudois, CHUV), Rue du Bugnon 46, CH-1011 Lausanne, Switzerland.
authors.forename: Monia
authors.initials: M
authors.lastname: Guidi
authors.affiliation: Division and Laboratory of Clinical Pharmacology, Service of Biomedicine, Department of Laboratories, Lausanne University Hospital (Centre Hospitalier Universitaire Vaudois, CHUV), Rue du Bugnon 46, CH-1011 Lausanne, Switzerland.
authors.forename: Chantal
authors.initials: C
authors.lastname: Csajka
authors.affiliation: Division and Laboratory of Clinical Pharmacology, Service of Biomedicine, Department of Laboratories, Lausanne University Hospital (Centre Hospitalier Universitaire Vaudois, CHUV), Rue du Bugnon 46, CH-1011 Lausanne, Switzerland.
authors.forename: Thierry
authors.initials: T
authors.lastname: Buclin
authors.affiliation: INSERM, ERI 23, 40 Avenue du Recteur Pineau, Poitiers 86000, France; Université of Poitiers, Faculty of Medicine and Pharmacy, and Centre Hospitalier Universitaire Poitiers, 2 Rue de la Milétrie, Poitiers 86000, France.
authors.forename: William
authors.initials: W
authors.lastname: Couet
authors.affiliation: Infectious Diseases Service, Department of Medicine, Lausanne University Hospital (Centre Hospitalier Universitaire Vaudois, CHUV), Lausanne, Switzerland.
authors.forename: Oscar
authors.initials: O
authors.lastname: Marchetti
authors.affiliation: Division and Laboratory of Clinical Pharmacology, Service of Biomedicine, Department of Laboratories, Lausanne University Hospital (Centre Hospitalier Universitaire Vaudois, CHUV), Rue du Bugnon 46, CH-1011 Lausanne, Switzerland. Electronic address: laurentarthur.decosterd@chuv.ch.
authors.forename: Laurent A
authors.initials: LA
authors.lastname: Decosterd
mesh_terms: D002138:Calibration; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D003091:Colistin / Q000031:analogs & derivatives* / Q000032:analysis*; D016903:Drug Monitoring / Q000379:methods; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D011112:Polymyxin B / Q000032:analysis*; D011355:Prodrugs / Q000032:analysis*; D052616:Solid Phase Extraction; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D011355:Prodrugs; C004691:colistinmethanesulfonic acid; D011112:Polymyxin B; D003091:Colistin
keywords: Anti-Gram negative antibiotic; Colistine; Colistine methanesulfonate; Hydrophilic interaction chromatography; Micro-elution solid-phase extraction