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Potential for methotrexate exposure through contamination during parenteral use as an immunosuppressant

L S Wong1, K E Tymms, N A Buckley

  • 1Department of Clinical Pharmacology and Toxicology, Canberra Hospital, Canberra, Australian Capital Territory, Australia. wlsan@yahoo.com

Internal Medicine Journal
|July 8, 2009
PubMed
Abstract

Insights

Methotrexate (MTX) skin contamination from 25 mg doses did not lead to significant toxicity in volunteers. Standard oncology handling precautions are unnecessary for rheumatology patients using lower MTX doses for autoimmune diseases.

Area of Science:

  • Pharmacology
  • Toxicology
  • Dermatology

Background:

  • Methotrexate (MTX) is an immunosuppressant drug used in treating autoimmune diseases.
  • Concerns exist regarding potential toxicity from skin contamination during MTX administration.

Purpose of the Study:

  • To assess the risk of MTX exposure via skin contamination with parenteral 25 mg doses.
  • To determine if special oncology handling precautions are warranted for rheumatology use.

Main Methods:

  • Six volunteers received deliberate skin exposure to 25 mg MTX solution for 30 minutes.
  • Serum MTX and homocysteine levels, 24-hour urinary MTX excretion, and toxicity signs were monitored.

Main Results:

  • All serum MTX concentrations remained below 0.02 micromol/L, significantly lower than levels requiring folinic acid supplementation.
  • No significant increase in homocysteine levels indicated MTX toxicity.
  • Mild local dermal reactions were the only adverse effects observed in three volunteers.

Conclusions:

  • Accidental skin contamination with 25 mg MTX did not result in significant systemic absorption or toxicity.
  • Oncology-level MTX handling precautions are likely unnecessary for rheumatology patients and carers using lower doses for autoimmune conditions.

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