Methotrexate is a folic acid antagonist and is classified as an antimetabolite cytotoxic agent. Methotrexate is used in the treatment of adults with severe, active, classical or definite rheumatoid arthritis who are unresponsive or intolerant to conventional therapy. Methotrexate has also been used in the treatment of severe, uncontrolled psoriasis, which is not responsive to other therapy. Methotrexate has been used to produce regression in a wide range of neoplastic conditions including acute leukaemias, non-Hodgkin's lymphoma, soft-tissue and osteogenic sarcomas, and solid tumours particularly breast, lung, head and neck, bladder, cervical, ovarian, and testicular carcinoma.