Learn about the side effects of methotrexate, from common to rare, for consumers and healthcare professionals. 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. 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 NHS medicines information on side effects of methotrexate and what you can do to cope. 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. INTRODUCTION Methotrexate (MTX) use can be associated with a variety of adverse effects over a wide range of severity (table 1); the risk of most adverse effects is influenced by the MTX dose and treatment regimen. Did you know methotrexate can cause side effects like hair loss and low blood cell count? Review all the severe and long-term side effects of methotrexate here. 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 a medication that treats arthritis, psoriasis and other inflammatory conditions. Learn more about its uses and side effects. Side Effects Prevention Tips The good news: These common side effects can often be short-circuited by taking a folic acid supplement. Folic acid is the synthetic form of folate. One study found that RA patients on methotrexate who took folic acid supplements lowered the risk of GI problems and mouth sores by 79%.