title: Late-onset delayed excretion of methotrexate.
abstract: Pleural effusions, ascites, and renal dysfunction decrease the plasma excretion of methotrexate (MTX). However, it is not known what effect these complications have on MTX clearance when they arise after the plasma MTX concentration has fallen to an undetectable level. We describe the clinical course and pharmacokinetics of MTX in a patient with acute lymphoblastic leukemia who experienced pleural effusions, ascites, and renal failure during the weeks after treatment with high-dose MTX (1.63 g/m2 i.v. over 24 h). The patient's normal initial MTX clearance rate (107 ml/min/m2) was consistent with his undetectable plasma level of MTX on day 9 after the infusion. His plasma MTX concentration then gradually increased as his renal function declined, reaching a peak of 0.72 microM on day 15. This unusual finding of an undetectable plasma MTX concentration that subsequently rose to persistent, potentially toxic levels was explained only by a pharmacokinetic model that accounted both for a third space at the time of treatment and for the subsequent decrease in the systemic elimination rate. Therefore, the finding of a physiologic third space during MTX administration combined with the detection of renal dysfunction in the following weeks should be an indication for prolonged therapeutic drug monitoring.
authors.affiliation: St Jude Children's Research Hospital, 332 North Lauderdale St, Memphis, TN 38105-2794, USA.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Pauley
authors.forename: John Carl
authors.initials: JC
authors.lastname: Panetta
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Schmidt
authors.forename: Nancy
authors.initials: N
authors.lastname: Kornegay
authors.forename: Mary V
authors.initials: MV
authors.lastname: Relling
authors.forename: Ching-Hon
authors.initials: CH
authors.lastname: Pui
mesh_terms: D000293:Adolescent; D000964:Antimetabolites, Antineoplastic / Q000009:adverse effects / Q000097:blood* / Q000493:pharmacokinetics*; D001201:Ascites / Q000150:complications*; D006801:Humans; D008297:Male; D008727:Methotrexate / Q000009:adverse effects / Q000097:blood* / Q000493:pharmacokinetics*; D010996:Pleural Effusion / Q000150:complications*; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000150:complications* / Q000188:drug therapy*; D051437:Renal Insufficiency / Q000150:complications*
chemical_list: D000964:Antimetabolites, Antineoplastic; D008727:Methotrexate