title: Population pharmacokinetics of high-dose methotrexate in Japanese adult patients with malignancies: a concurrent analysis of the serum and urine concentration data.
abstract: OBJECTIVE
  This study aimed to develop a population pharmacokinetic model for high-dose methotrexate (MTX), specifically focusing on the drug urinary excretion process.
  
  
  RESULTS
  Three hundred and forty-eight serum samples and 416 urine samples from 51 Japanese adult patients with malignancies were concurrently fitted into a multi-compartment model using the nonmem program. In the final model, creatinine clearance (CCR, mL/min) and the MTX dose (DOSE10G; 0 when <10 g, 1 when >or=10 g) were the most significant factors that affected the renal clearance (CL(r)) and non-renal clearance (CL(nr)), respectively: CL(r)(L/h) = 5.57 x (CCR/80.0)(0.112), V(1)(L) = 26.9, Q(L/h) = 0.0778, V(2)(L) = 2.27, CL(nr)(L/h) = 0.567 x 3.39(DOSE10G), where V(1) and V(2) are the volumes of distribution of the central and peripheral compartments, respectively, and Q is the inter-compartmental (central-peripheral) clearance. For another nine patients, the model enabled a satisfactory Bayesian estimation using two time-point serum concentrations.
  
  
  CONCLUSIONS
  The newly developed population pharmacokinetic model should improve the quality of serum concentration monitoring of high-dose MTX to predict and control toxic events.
authors.affiliation: Department of Clinical Pharmacotherapy, Hiroshima University, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Fukuhara
authors.forename: K
authors.initials: K
authors.lastname: Ikawa
authors.forename: N
authors.initials: N
authors.lastname: Morikawa
authors.forename: K
authors.initials: K
authors.lastname: Kumagai
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000964:Antimetabolites, Antineoplastic / Q000008:administration & dosage / Q000009:adverse effects / Q000493:pharmacokinetics*; D001499:Bayes Theorem; D003404:Creatinine / Q000097:blood / Q000652:urine; D004305:Dose-Response Relationship, Drug; D016903:Drug Monitoring / Q000379:methods; D005260:Female; D005544:Forecasting; D006801:Humans; D007564:Japan; D008297:Male; D008727:Methotrexate / Q000008:administration & dosage / Q000009:adverse effects / Q000493:pharmacokinetics*; D008875:Middle Aged; D008954:Models, Biological; D009369:Neoplasms / Q000188:drug therapy*; D017711:Nonlinear Dynamics; D012189:Retrospective Studies; D012984:Software; D014018:Tissue Distribution; D055815:Young Adult
chemical_list: D000964:Antimetabolites, Antineoplastic; D003404:Creatinine; D008727:Methotrexate