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Abstract: TH-PO149

DAMPAned Methotrexate Levels: A Case Report of Acute Methotrexate Toxicity

Session Information

Category: Trainee Case Report

  • 1500 Onco-Nephrology

Authors

  • Young, Ann, University of Toronto, Toronto, Ontario, Canada
  • Perl, Jeffrey, St. Michael's Hospital, Toronto, Ontario, Canada
Introduction

New guidelines exist on the management of methotrexate-induced nephrotoxicity, focusing on the use of glucarpidase (Voraxaze®). We describe an application of these guidelines and highlight nuances around drug procurement and post-intervention laboratory monitoring.

Case Description

A 61-year old male with diffuse large B-cell lymphoma (DLBCL) with cerebral involvement was admitted for his first cycle of high-dose methotrexate (HDMTX). He previously received two cycles of R-CHOP chemotherapy. Baseline serum creatinine (SCr) was 63 µmol/L. Following HDMTX, his methotrexate level was 175 µmol/L. Despite extracellular volume expansion, urinary alkalinization, and leucovorin rescue, he developed severe acute kidney injury (SCr 374 µmol/L) and subsequently went into status epilepticus. He was given glucarpidase at 52-hours post-HDMTX. Methotrexate level 8 hours after glucarpidase was 7.26 µmol/L by immunoassay, but <0.05 µmol/L by mass spectrometry. Interference due to the DAMPA metabolite resulted in falsely elevated levels by immunoassay for > 5 days after glucarpidase administration. He remained non-oliguric. Serum creatinine peaked at 608 µmol/L then trended down. He ultimately avoided the need for dialysis and had full renal and neurologic recovery.

Discussion

Glucarpidase is an effective option for non-renal elimination of toxic methotrexate concentrations in patients with nephrotoxicity. Awareness of how to access the drug, protocolization of monitoring including specific laboratory requirements, and knowledge of alternative treatments is necessary for centres where HDMTX therapy is used.