Methotrexate is a pharmaceutical that inhibits the action of folic acid. It is often used in the treatment of cancer, particularly for paraneoplastic syndrome and as part of a chemotherapy regimen. It is also used to treat certain types of autoimmune diseases. It can be taken orally or injected. Methotrexate can be used to induce an abortion and is often used to treat ectopic pregnancy. Methotrexate's side effects include anemia, nausea, and diarrhea. It can also affect liver function.