1H-Carbazol-4-one, 2,3-dihydro-9-methyl-3-((2-methylimidazol-1-yl)methyl)-, hydrochloride, dihydrate 9-Methyl-3-((2-methylimidazol-1-yl)methyl)-2,3-dihydro-1H-carbazol-4-one hydrochloride 2H2O FE6373975 Ondansetron hydrochloride