title: Test dose for predicting high-dose methotrexate infusions.
abstract: Eighteen evaluable patients were studied to determine whether individual methotrexate (MTX) kinetics, determined by test-dose bolus injection, could be used to predict plasma drug concentrations during and after high-dose infusion. Small nontoxic doses of MTX (10 mg/m2) was given to patients who were followed for 12 to 24 hr and the kinetic data were used to predict subsequent kinetic behavior of moderate- and high-dose methotrexate infusions (150 to 1500 mg/m2 over 12 to 18 hr). After test-dose injection, MTX clearance varied from 36 to 138 ml/min/m2 and decreased with advancing age (r = -0.49, P less than 0.05). MTX clearance varied from 24 to 100 ml/min/m2 after high-doses. Although there was a trend to decreasing clearance with advancing age, this was not as clear as with the test dose (r = -0.42, P greater than 0.05). There was no correlation between MTX clearance and creatinine clearance in this group of patients in whom creatinine clearance varied from 32 to 63 ml/min/m2. When the kinetic parameters derived from the test-dose data were used, accurate predictions could be made of the infusion plateau (r = 0.89, P less than 0.001) and 24-hr (r = 0.92, P less than 0.001) MTX concentrations after high-dose infusions. Our results indicate that test-dose MTX kinetics may serve as a guide to dose modification of MTX infusions in some high-risk patients.
mesh_terms: D000328:Adult; D000368:Aged; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D007263:Infusions, Parenteral; D007700:Kinetics; D008223:Lymphoma / Q000188:drug therapy / Q000378:metabolism*; D008297:Male; D008727:Methotrexate / Q000097:blood / Q000378:metabolism* / Q000627:therapeutic use; D008875:Middle Aged
chemical_list: D008727:Methotrexate