- A drug used alone or with other drugs to treat many types of cancer, certain types of arthritis, and severe psoriasis (a type of skin condition). It is also being studied in the treatment of other conditions and types of cancer. Methotrexate sodium stops cells from using folic acid to make DNA and may kill cancer cells. It may also lower the body’s immune response. Methotrexate sodium is a type of antimetabolite and a type of antifolate. Also called MTX, Trexall, and Xatmep.