Laboratory Medicine Program

Methotrexate
(MTX, amethopterin)

Clinical Decription:
Methotrexate (MTX, amethopterin) is a folate antimetabolite. It is an analog of aminopterin, which is also derived from folic acid. The molecular structure of methotrexate differs from folic acid in that it has a hydroxyl group in place of the 4-amino group on the pteridine ring and there is no methyl group at the N position. Methotrexate is an antineoplastic drug used solely or in combination with other antineoplastic drugs for the treatment of leukemia and other diseases. Relatively low doses of methotrexate have been used in the treatment of nonmalignant diseases such as severe psoriasis, asthma, rheumatoid arthritis, sarcoidosis, and transplantation therapy. Intermediate to high doses of methotrexate with Leucovorin rescue have been used with favorable results in the treatment of osteogenic sarcoma, leukemia, non-Hodgkin’s lymphoma, lung and breast cancer. Methotrexate levels are monitored to avoid excessive toxic effects of the drug and to determine when to intervene with counter-acting ‘rescue’ therapy. Adverse reactions include myelosuppression, stomatitis, nausea, vomiting, convulsions, liver and renal abnormalities, anemia, leukopenia, thrombocytopenia, osteoporosis, neurotoxicity, and leukoencephalopathy.

Method: Chemiluminescent Microparticle Immunoassay; Alinity i

Component Tests Used: n/a

Reference Ranges Used:
Both the therapeutic and toxic ranges for Methotrexate are protocol dependent.

Specimen Type: Serum
Volume: 1 mL (minimum: 1 mL)

Shipping: Refrigerated 2-8C (send on ice or freeze packs)

Special Instructions: Ship aliquot of serum or plasma at 2-8°C (wet ice) or frozen (dry ice)

Testing Schedule(s): Daily.

Turnaround Time: STAT 1 hour

For more information, call 416.340.5227 or 1.866.865.5227