FK 888 is primarily used in research settings as a selective antagonist for the neurokinin-1 (NK1) receptor. It plays a significant role in studying the physiological and pathological functions of substance P, a neuropeptide involved in pain transmission, inflammation, and emotional regulation. Researchers utilize FK 888 to investigate its potential in managing conditions like chronic pain, migraines, and anxiety disorders. Additionally, it aids in exploring the mechanisms of neurokinin signaling pathways, contributing to the development of novel therapeutic agents targeting the NK1 receptor. Its application extends to preclinical studies aimed at understanding its efficacy and safety in various disease models.