Flutamide is an antiandrogen drug, with its active metablolite binding at androgen receptor with Ki values of 55 nM, and primarily used to treat prostate cancer. Target: androgen receptor in vitro: Flutamide (Eulexin) is an antiandrogen drug. Flutamide-OH, the active metabolite of flutamide, directly binds at rat anterior pituitary androgen receptor with Ki values of 55 nM [1]. lutamide does not affect the proliferation of an androgen-sensitive clone of the mouse mammary carcinoma Shionogi SC-l 15 cells in culture, shows only antiandrogenic effect, but not androgenic effect [2]. Flutamide provides treatment for prostate cancer when used along with leuprolide [3]. in vivo: Flutamide causes a markedly reduction in rat ventral prostate weight from 319 mg to 245 mg. A combination of flutamide and LHRH agonist induces an additive effect with a decrease in prostate weight to 101 mg, and an marked drop in prostatic ODC activity [4].