Question: what are the side effects of long term use of methotrexate?
Answer: If you are using methotrexate long term, a liver biopsy is usually recommended. Methotrexate use has rarely caused serious (sometimes fatal) side effects, such as lung problems, lung infections (Pneumocystis jiroveci pneumonia), skin reactions, diarrhea, and mouth sores (ulcerative stomatitis).