Bottle of methotrexate. Methotrexate 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 originally synthesized by the Indian biochemist Yellapragada Subbarow and clinically developed by the American pediatrician Sidney Farber. It is on the World Health Organization's List of Essential Medicines, a list of the most important medications needed in a basic health system. No photographer credited, undated.