trade names: Folex, Mexate, Rheumatrex; drug class: folic acid antagonist, antineoplastic; action: inhibits an enzyme that reduces folic acid, which is needed for nucleic acid synthesis in all cells; uses: acute lymphocytic leukemia; in combination for breast, lung, head, neck cancer; lymphosarcoma, psoriasis; gestational choriocarcinoma, hydatid mole.