This test is used to evaluate and detect toxic concentrations of methotrexate. Methotrexate is an antiplastic agent that prevents the DNA synthesis and is used in treating acute lymphocytic leukemia, lymphoma, and cancers of head, neck, lung, and breast. Serum concentrations of methotrexate are usually monitored during high dose therapy (>50mg/m{2}) to identify the time at which active intervention by leucovorin rescue must be initiated.
