Noun | 1. | methotrexate sodium - toxic antimetabolite that limits cellular reproduction by acting as an antagonist to folic acid; used to treat certain cancers and psoriasis and rheumatoid arthritis antimetabolite - an antineoplastic drug that inhibits the utilization of a metabolite immune suppressant drug, immunosuppressant, immunosuppressive, immunosuppressive drug, immunosuppressor - a drug that lowers the body's normal immune response |