title: Population Pharmacokinetics of Intravenous Methotrexate in Patients with Hematological Malignancies: Utilization of Routine Clinical Monitoring Parameters.
abstract: OBJECTIVE
  Clinical response to methotrexate in cancer is variable and depends on several factors including serum drug exposure. This study aimed to develop a population pharmacokinetic model describing methotrexate disposition in cancer patients using retrospective chart review data available from routine clinical practice.
  
  
  METHODS
  A retrospective review of medical records was conducted for cancer patients in Qatar. Relevant data (methotrexate dosing/concentrations from multiple occasions, patient history, and laboratory values) were extracted and analyzed using NONMEM VII®. A population pharmacokinetic model was developed and used to estimate inter-individual and inter-occasion variability terms on methotrexate pharmacokinetic parameters, as well as patient factors affecting methotrexate pharmacokinetics.
  
  
  RESULTS
  Methotrexate disposition was described by a two-compartment model with clearance (CL) of 15.7 L/h and central volume of distribution (Vc) of 79.2 L. Patient weight and hematocrit levels were significant covariates on methotrexate Vcand CL, respectively. Methotrexate CL changed by 50 % with changes in hematocrit levels from 23 to 50 %. Inter-occasion variability in methotrexate CL was estimated for patients administered the drug on multiple occasions (48 and 31 % for 2nd and 3rd visits, respectively).
  
  
  CONCLUSIONS
  Therapeutic drug monitoring data collected during routine clinical practice can provide a useful tool for understanding factors affecting methotrexate pharmacokinetics. Patient weight and hematocrit levels may play a clinically important role in determining methotrexate serum exposure and dosing requirements. Future prospective studies are needed to validate results of the developed model and evaluate its usefulness to predict methotrexate exposure and optimize dosing regimens.
authors.affiliation: Qatar University College of Pharmacy, Doha, Qatar. naderpgp@gmail.com.|AbbVie, Inc, North Chicago, USA. naderpgp@gmail.com.
authors.forename: Ahmed
authors.initials: A
authors.lastname: Nader
authors.affiliation: Qatar University College of Pharmacy, Doha, Qatar.
authors.forename: Noran
authors.initials: N
authors.lastname: Zahran
authors.affiliation: Qatar University College of Pharmacy, Doha, Qatar.
authors.forename: Aya
authors.initials: A
authors.lastname: Alshammaa
authors.affiliation: Qatar University College of Pharmacy, Doha, Qatar.
authors.forename: Heba
authors.initials: H
authors.lastname: Altaweel
authors.affiliation: Hamad Medical Corporation, Doha, Qatar.
authors.forename: Nancy
authors.initials: N
authors.lastname: Kassem
authors.affiliation: Qatar University College of Pharmacy, Doha, Qatar.
authors.forename: Kyle John
authors.initials: KJ
authors.lastname: Wilby
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000964:Antimetabolites, Antineoplastic / Q000008:administration & dosage / Q000493:pharmacokinetics*; D001835:Body Weight; D004305:Dose-Response Relationship, Drug; D016903:Drug Monitoring / Q000379:methods*; D005260:Female; D006400:Hematocrit; D019337:Hematologic Neoplasms / Q000188:drug therapy*; D006801:Humans; D008297:Male; D008727:Methotrexate / Q000008:administration & dosage / Q000493:pharmacokinetics*; D008875:Middle Aged; D008954:Models, Biological; D017711:Nonlinear Dynamics; D011780:Qatar; D012189:Retrospective Studies; D014018:Tissue Distribution; D055815:Young Adult
chemical_list: D000964:Antimetabolites, Antineoplastic; D008727:Methotrexate