The hydrochloride salt of ramosetron, a selective serotonin (5-HT) receptor antagonist with potential antiemetic activity. Upon administration, ramosetron selectively binds to and blocks the activity of 5-HT subtype 3 (5-HT3) receptors located in the vagus nerve terminal and in the vomiting center in the central nervous system (CNS), suppressing chemotherapy-induced nausea and vomiting.