Methotrexate (MTX)

General Information

Methotrexate (MTX, formerly known as amethopterin) is an antimetabolite and antifolate drug. In high doses, MTX is used to treat choriocarcinoma, leukemia in the spinal fluid, osteosarcoma, breast cancer, lung cancer, non-Hodgkin lymphoma and head and neck cancers. In these patients, careful monitoring of MTX is required. High dose MTX patients should be monitored at 24hr, 48hr and 72hr post infusion until levels fall to <0.01. results  are needed same day to assess need for rescue  preparation when levels remain high over a longe period p. MTX may also be used, in much lower doses and most commonly is a GP setting, to treat rheumatoid arthritis, psoriasis and other autoimmune disorders. The doses in these patients are small, therefore have concentrations less than the limit of detection of the laboratory assay. Thus in these patients monitor MTX toxicity by measurement of amino transferases or Pro-collagen peptide Type 3 (P3NP).

Patient Preparation

For high dose IV regimes only.

Low dose methotrexate - monitoring not required.

Notes