title: A New Method to Quantify Ifosfamide Blood Levels Using Dried Blood Spots and UPLC-MS/MS in Paediatric Patients with Embryonic Solid Tumours.
abstract: Ifosfamide blood concentrations are necessary to monitor its therapeutic response, avoiding any adverse effect. We developed and validated an analytical method by UPLC-MS/MS to quantify ifosfamide in dried blood spots (DBS). Blood samples were collected on Whatman 903® filter paper cards. Five 3 mm disks were punched out from each dried blood spot. Acetonitrile and ethyl acetate were used for drug extraction. Chromatographic separation was carried out in an Acquity UPLC equipment with a BEH-C18 column, 2.1 x 100 mm, 1.7 μm (Waters®). The mobile phase consisted in 5 mM ammonium formate and methanol:acetonitrile (40:48:12 v/v/v) at 0.2 mL/min. LC-MS/MS detection was done by ESI+ and multiple reaction mode monitoring, ionic transitions were m/z1+ 260.99 > 91.63 for ifosfamide and 261.00 > 139.90 for cyclophosphamide (internal standard). This method was linear within a 100-10000 ng/mL range and it was accurate, precise and selective. Ifosfamide samples in DBS were stable for up to 52 days at -80°C. The procedure was tested in 14 patients, ages 1 month to 17 years (9 males and 5 females), with embryonic tumours treated with ifosfamide, alone or combined, at a public tertiary referral hospital. Ifosfamide blood levels ranged from 11.1 to 39.7 μmol/L at 12 hours after the last infusion, while 24-hour levels ranged from 0.7-19.7 μmol/L. The median at 12 hours was 19.5 μmol/L (Q25 14.4-Q75 29.0) and 3.8 μmol/L (Q25 1.5-Q75 9.9) at 24 hours, p<0.001. This method is feasible to determine ifosfamide plasma levels in paediatric patients.
authors.affiliation: Laboratorio de Farmacología, Instituto Nacional de Pediatría, Mexico City, Mexico.
authors.forename: Luz-María
authors.initials: LM
authors.lastname: Torres
authors.affiliation: Laboratorio de Farmacología, Instituto Nacional de Pediatría, Mexico City, Mexico.
authors.forename: Liliana
authors.initials: L
authors.lastname: Rivera-Espinosa
authors.affiliation: Laboratorio de Farmacología, Instituto Nacional de Pediatría, Mexico City, Mexico.
authors.forename: Juan L
authors.initials: JL
authors.lastname: Chávez-Pacheco
authors.affiliation: Laboratorio de Farmacología, Instituto Nacional de Pediatría, Mexico City, Mexico.|Facultad de Estudios Superiores Iztacala, Universidad Nacional Autónoma de México, Mexico City, Mexico.
authors.forename: Carlos F
authors.initials: CF
authors.lastname: Navas
authors.affiliation: Laboratorio de Farmacología, Instituto Nacional de Pediatría, Mexico City, Mexico.
authors.forename: Joel A
authors.initials: JA
authors.lastname: Demetrio
authors.affiliation: Laboratorio de Farmacología, Instituto Nacional de Pediatría, Mexico City, Mexico.
authors.forename: Radamés
authors.initials: R
authors.lastname: Alemón-Medina
authors.affiliation: Laboratorio de Farmacología, Instituto Nacional de Pediatría, Mexico City, Mexico.
authors.forename: Francisca
authors.initials: F
authors.lastname: Trujillo
authors.affiliation: Servicio de Oncología, Instituto Nacional de Pediatría, Mexico City, Mexico.
authors.forename: Martín
authors.initials: M
authors.lastname: Pérez
authors.affiliation: Servicio de Oncología, Instituto Nacional de Pediatría, Mexico City, Mexico.
authors.forename: Martha M
authors.initials: MM
authors.lastname: Zapata
authors.affiliation: Servicio de Oncología, Instituto Nacional de Pediatría, Mexico City, Mexico.
authors.forename: Rocío
authors.initials: R
authors.lastname: Cárdenas
authors.affiliation: Laboratorio de Neuropatología, Instituto Nacional de Neurología y Neurocirugía, Mexico City, Mexico.
authors.forename: Citlaltepetl
authors.initials: C
authors.lastname: Salinas
authors.affiliation: Laboratorio de Genómica del Cáncer, Instituto Nacional de Enfermedades Respiratorias, Mexico City, Mexico.
authors.forename: Arnoldo
authors.initials: A
authors.lastname: Aquino
authors.affiliation: Laboratorio de Genómica del Metabolismo Óseo, Instituto Nacional de Medicina Genómica, Mexico City, Mexico.
authors.forename: Rafael
authors.initials: R
authors.lastname: Velázquez-Cruz
authors.affiliation: Unidad de Vigilancia Epidemiológica, Instituto Nacional de Enfermedades Respiratorias, Mexico City, Mexico.
authors.forename: Manuel-de-Jesús
authors.initials: MD
authors.lastname: Castillejos
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D003520:Cyclophosphamide; D003710:Demography; D059788:Dried Blood Spot Testing / Q000379:methods*; D005260:Female; D006400:Hematocrit; D006801:Humans; D007069:Ifosfamide / Q000097:blood*; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D009373:Neoplasms, Germ Cell and Embryonal / Q000097:blood*; D015203:Reproducibility of Results; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D003520:Cyclophosphamide; D007069:Ifosfamide