One of the ANTIMETABOLITES used to treat certain forms of malignant disease. It is given orally, intravenously, intramuscularly or intrathecally. It is particularly used as maintenance therapy for childhood acute lymphoblastic LEUKAEMIA. Other uses include CHORIOCARCINOMA, NON-HODGKIN'S LYMPHOMA (NHL) and various solid tumours.

It is also used for severe uncontrolled PSORIASIS unresponsive to conventional therapy and sometimes in severe active RHEUMATOID ARTHRITIS. Because of its potentially severe haematological, pulmonary, gastrointestinal, and other toxicities it should be prescribed and supervised by specialists.