Methotrexate testing is used following high dose chemotherapy, serum concentration are used to judge whether the drug is being cleared appropriately and verify that a nontoxic level has been attained.
Methotrexate is an antineoplastic agent that inhibits the enzyme, dihydrofolate reductase. Such inhibition causes a stoppage of synthesis of tetrahydrofolate that, in turn, results in an inhibition of nucleotide and ultimately of DNA synthesis. It has come into use as a treatment for some autoimmune diseases, including myasthenia gravis, polymyositis, dermatomyositis, inclusion body myositis, ankylosing spondylitis, Crohn’s disease, psoriasis, pustular soriasis, systemic lupus erythematosus, psoriatic arthritis, rheumatoid arthritis, Wegener’s granulomatosis, Adult-onset Still’s disease, andscleroderma. A parallel use with TNFα blockers, such as adalimumab, infliximab, or etanercept, has been shown to markedly improve symptoms.Methotrexate is effective against malignancies with rapid cell proliferation such as acute lymphoblastic leukemia, choriocarcinoma, trophoblastic tumours in women, and carcinomas of the breast, tongue, pharynx, and testis.
When used as an antineoplastic agent against these tumours, it is administered at high dose, so concentrations must be checked periodically to maintain that the patient’s is not at toxic levels.
There is no reference ranges quoted, treatment specific protocols should indicate the level expected.
Serum – Plain (red) or SST suitable. EDTA plasma is unacceptable
For monitoring oncology patients on high dose therapy only. Levels are usually required following high dose for leukaemia, levels should be <0.1µmol/L before discharge of cancer patients.
Royal Victoria Hospital