title: Therapeutic drug monitoring of carbamazepine and its metabolite in children from dried blood spots using liquid chromatography and tandem mass spectrometry.
abstract: Carbamazepine (CBZ) is a first-line drug for the treatment of different forms of epilepsy and the first choice drug for trigeminal neuralgia. CBZ is metabolized in the liver by oxidation into carbamazepine-10,11-epoxide (CBZE), its major metabolite which is equipotent and known to contribute to the pharmacological activity of CBZ. The aim of the present study was to develop and validate a reliable, selective and sensitive liquid chromatography-tandem mass spectrometry method for the simultaneous quantification of CBZ and its active metabolite in dried blood spots (DBS). The extraction process was carried out from DBS using methanol-water-formic acid (80:20:0.1, v/v/v). Chromatographic elution was achieved by using a linear gradient with a mobile phase consisting of acetonitrile-water-0.1% formic acid at a flow rate of 0.50mL/min. The method was linear over the range 1-40mg/L and 0.25-20mg/L for CBZ and CBZE, respectively. The limit of quantification was 0.75mg/L and 0.25mg/L for CBZ and CBZE. Intra-day and inter-day assay precisions were found to be lower than 5.13%, 6.46% and 11.76%, 4.72% with mean percentage accuracies of 102.1%, 97.5% and 99.2%, 97.8% for CBZ and CBZE. We successfully applied the method for determining DBS finger-prick samples in paediatric patients and confirmed the results with concentrations measured in matched plasma samples. This novel approach allows quantification of CBZ and its metabolite from only one 3.2mm DBS disc by LC-MS/MS thus combining advantages of DBS technique and LC-MS/MS in clinical practice.
authors.affiliation: Pharmaceutical Chemistry Department, Faculty of Pharmacy, Future University in Egypt, Egypt.
authors.forename: Engy
authors.initials: E
authors.lastname: Shokry
authors.affiliation: Newborn Screening, Biochemistry and Pharmacology Laboratories, Department of Neurosciences, Meyer University Children's Hospital, Florence, Italy.
authors.forename: Fabio
authors.initials: F
authors.lastname: Villanelli
authors.affiliation: Newborn Screening, Biochemistry and Pharmacology Laboratories, Department of Neurosciences, Meyer University Children's Hospital, Florence, Italy.
authors.forename: Sabrina
authors.initials: S
authors.lastname: Malvagia
authors.affiliation: Pediatric Neurology Unit, Meyer University Children's Hospital, Florence, Department of Neurosciences, University of Florence, Italy.
authors.forename: Anna
authors.initials: A
authors.lastname: Rosati
authors.affiliation: Newborn Screening, Biochemistry and Pharmacology Laboratories, Department of Neurosciences, Meyer University Children's Hospital, Florence, Italy.
authors.forename: Giulia
authors.initials: G
authors.lastname: Forni
authors.affiliation: Newborn Screening, Biochemistry and Pharmacology Laboratories, Department of Neurosciences, Meyer University Children's Hospital, Florence, Italy.
authors.forename: Silvia
authors.initials: S
authors.lastname: Funghini
authors.affiliation: Newborn Screening, Biochemistry and Pharmacology Laboratories, Department of Neurosciences, Meyer University Children's Hospital, Florence, Italy.
authors.forename: Daniela
authors.initials: D
authors.lastname: Ombrone
authors.affiliation: Newborn Screening, Biochemistry and Pharmacology Laboratories, Department of Neurosciences, Meyer University Children's Hospital, Florence, Italy.
authors.forename: Maria
authors.initials: M
authors.lastname: Della Bona
authors.affiliation: Newborn Screening, Biochemistry and Pharmacology Laboratories, Department of Neurosciences, Meyer University Children's Hospital, Florence, Italy; Pediatric Neurology Unit, Meyer University Children's Hospital, Florence, Department of Neurosciences, University of Florence, Italy; Department of Neuroscience, Psychology, Drug Research and Child Health, University of Florence, Italy.
authors.forename: Renzo
authors.initials: R
authors.lastname: Guerrini
authors.affiliation: Newborn Screening, Biochemistry and Pharmacology Laboratories, Department of Neurosciences, Meyer University Children's Hospital, Florence, Italy; Department of Neuroscience, Psychology, Drug Research and Child Health, University of Florence, Italy. Electronic address: g.lamarca@meyer.it.
authors.forename: Giancarlo
authors.initials: G
authors.lastname: la Marca
mesh_terms: D000293:Adolescent; D000927:Anticonvulsants / Q000097:blood*; D001711:Biotransformation; D002138:Calibration; D002220:Carbamazepine / Q000097:blood*; D002648:Child; D002675:Child, Preschool; D002851:Chromatography, High Pressure Liquid; D016903:Drug Monitoring / Q000379:methods*; D005260:Female; D006400:Hematocrit; D006801:Humans; D007223:Infant; D057230:Limit of Detection; D008297:Male; D012015:Reference Standards; D015203:Reproducibility of Results; D013048:Specimen Handling; D053719:Tandem Mass Spectrometry
chemical_list: D000927:Anticonvulsants; D002220:Carbamazepine
keywords: Carbamazepine; Carbamazepine-10,11-epoxide; Dried blood spots; LC–MS/MS; Therapeutic drug monitoring