Please consult your physician before taking any medication. Generic Name: methotrexate (meth oh TREX ate) Brand Names: Rheumatrex Dose Pack, Trexall What is Rheumatrex (methotrexate)? Methotrexate interferes with the growth of certain cells of the body, especially cells that reproduce quickly, such as cancer cells, bone marrow cells, and skin cells. Methotrexate is used to treat certain types of cancer of the breast, skin, head and neck, or lung. Methotrexate is also used to treat severe psoriasis and rheumatoid arthritis. Methotrexate is usually given after other medications have been tried without successful treatment of symptoms. Methotrexate may also be used for purposes other than those listed in this medication guide.