Fadrozole hydrochloride is a nonsteroidal aromatase inhibitor exhibiting a very potent and selective inhibitory effect of the aromatase enzyme system in vitro and estrogen biosynthesis in vivo. Fadrozole hydrochloride has been studied as a potential breast cancer regressor due to its ability to reduce estrogen synthesis. Fadrozole hydrochloride is a nonsteroidal aromatase inhibitor exhibiting a very potent and selective inhibitory effect of the aromatase enzyme system in vitro and estrogen biosynthesis in vivo. Fadrozole hydrochloride has been studied as a potential breast cancer regressor due to its ability to reduce estrogen synthesis.