Estramustine (INN, USAN, BAN) (brand names Emcyt, Estracit), in salt form as estramustine phosphate sodium (USAN) (or estramustine sodium phosphate (BAN)) or estramustine phosphate meglumine, is an alkylating antineoplastic agent (that is, a chemotherapeutic) that is used in the treatment of prostate cancer throughout the world.