A New Method to Quantify Ifosfamide Blood Levels Using Dried Blood Spots and UPLC-MS/MS in Paediatric Patients with Embryonic Solid Tumours

• Published in: PloS one Vol. 10; no. 11; p. e0143421
• Main Authors: Torres, Luz-María, Rivera-Espinosa, Liliana, Chávez-Pacheco, Juan L, Navas, Carlos F, Demetrio, Joel A, Alemón-Medina, Radamés, Trujillo, Francisca, Pérez, Martín, Zapata, Martha M, Cárdenas, Rocío, Salinas, Citlaltepetl, Aquino, Arnoldo, Velázquez-Cruz, Rafael, Castillejos, Manuel-de-Jesús
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 23.11.2015; Public Library of Science (PLoS)
• Subjects: Acetic acid; Acetonitrile; Adolescent; Ammonium; Blood; Blood levels; Cancer therapies; Cancer treatment; Child; Child, Preschool; Chromatography; Chromatography, High Pressure Liquid - methods; Cyclophosphamide; Demography; Disk filters; Dosage and administration; Dried Blood Spot Testing - methods; Drug metabolism; Drugs; Embryos; Ethyl acetate; Ewings sarcoma; Female; Females; Filter paper; Hematocrit; Humans; Ifosfamide; Ifosfamide - blood; Infant; Infant, Newborn; Infusion; Ions; Liquid chromatography; Male; Males; Mass spectrometry; Metabolism; Metabolites; Methods; Neoplasms, Germ Cell and Embryonal - blood; Patient outcomes; Patients; Physiological aspects; Plasma levels; Quality control; Reproducibility of Results; Scientific imaging; Solid tumors; Tandem Mass Spectrometry - methods; Toxicity; Tumors; United Kingdom > UK; United States > US; Mexico
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0143421

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.