A small molecule, high-affinity substance P antagonist (SPA) with antiemetic activity. Crossing the blood brain barrier, aprepitant binds selectively to the human substance P/neurokinin 1 receptor in the central nervous system (CNS), thereby inhibiting receptor binding of endogenous substance P and substance P-induced emesis. This agent has little or no affinity for serotonin type 3 (5-HT3), dopamine, and corticosteroid receptors. or A small, fingerlike pouch that sticks out from the cecum (the first part of the large intestine near the end of the small intestine).