Methotrexate (rINN), abbreviated MTX and formerly known as amethopterin, is an antimetabolite and antifolate drug. It is used in treatment of cancer, autoimmune diseases, ectopic pregnancy, and for the induction of medical abortions. It acts by inhibiting the metabolism of folic acid. Methotrexate began to replace the more toxic antifolate aminopterin starting in the 1950s. The drug was developed by Yellapragada Subbarao.
Methotrexate was originally developed and continues to be used for chemotherapy either alone or in combination with other agents. It is effective for the treatment of a number of cancers including: breast, head and neck, leukemia, lymphoma, lung, osteosarcoma, bladder, and trophoblastic neoplasms.[
It is used as a treatment for some autoimmune diseases including: rheumatoid arthritis, psoriasis, psoriatic arthritis, lupus and Crohn's disease, to name a few. Although methotrexate was originally designed as a chemotherapy drug (in high doses), in low doses methotrexate is a generally safe and well tolerated drug in the treatment of certain autoimmune diseases. Because of its effectiveness, low-dose methotrexate is now first-line therapy for the treatment of rheumatoid arthritis. Though methotrexate for autoimmune diseases is taken in lower doses than that of cancer, side effects such as hair loss, nausea, headaches, and skin pigmentation are still common.  Though not everybody is responsive to treatment with methotrexate, multiple studies and reviews showed that the majority patients receiving methotrexate for up to 1 year had less pain, functioned better, had fewer swollen and tender joints, and had less disease activity overall as reported by themselves and their doctors. X-rays also showed that the progress of the disease slowed or stopped in many patients receiving methotrexate.
It has also been used for multiple sclerosis but is not approved by the Food and Drug Administration.
Methotrexate is commonly used (generally in combination with misoprostol) to terminate pregnancies during the early stages (i.e., as an abortifacient). It is also used to treat ectopic pregnancies.
It can be taken orally or administered by injection (intramuscular, intravenous, subcutaneous, or intrathecal). Oral doses are taken weekly not daily. Routine monitoring of the complete blood count, liver function tests, and creatinine are recommended. Measurements of creatinine are recommended at least every 2 months.