Methotrexate is a medication that treats arthritis, psoriasis and other inflammatory conditions. Learn more about its uses and side effects. Find patient medical information for Methotrexate (Rheumatrex, Trexall, and others) on WebMD including its uses, side effects and safety, interactions, pictures, warnings, and user ratings Methotrexate, formerly known as amethopterin, is a chemotherapy agent and immune-system suppressant. It is used to treat cancer, autoimmune diseases, and ectopic pregnancies. It is used for cancers such as breast cancer, leukemia, lung cancer, lymphoma, gestational trophoblastic disease, and osteosarcoma, as well as autoimmune diseases such as psoriasis, rheumatoid arthritis, and Crohn's. NHS medicines information on methotrexate – what it's used for, side effects, dosage and who can take it. Methotrexate treats certain leukemias and lymphomas, mycosis fungoides, rheumatoid arthritis, polyarticular juvenile idiopathic arthritis in children, and severe psoriasis in adults. Learn about side effects, interactions, and indications. Description Methotrexate tablet is used alone or together with other medicines to treat several types of cancer, such as breast, head and neck, lung, blood (eg, acute lymphoblastic leukemia or ALL), bone, lymph node (eg, mycosis fungoides, relapsed or refractory non-Hodgkin lymphoma), or uterus cancer. Methotrexate is used to treat severe psoriasis (a skin disease in which red, scaly patches form on some areas of the body). Methotrexate is also used to treat rheumatoid arthritis (RA; a condition in which the body attacks its own joints, causing pain, swelling, and loss of function). Methotrexate is also used in children to treat polyarticular juvenile idiopathic arthritis (PJIA; a type of. Methotrexate (Rheumatrex, Trexall, Otrexup, Rasuvo) Methotrexate is one of the commonly used medications in the treatment of rheumatoid arthritis. It may also be used to treat lupus, inflammatory myositis, vasculitis, psoriasis, psoriatic arthritis, scleroderma, and some forms of childhood arthritis. Learn how methotrexate went from a cancer drug to a staple treatment for rheumatoid arthritis and other types of inflammatory arthritis conditions. Learn about the side effects of methotrexate, from common to rare, for consumers and healthcare professionals.