The active ingredient in LOTRONEX Tablets is alosetron hydrochloride
(HCl), a potent and selective antagonist of the serotonin 5-HT3 receptor
type. Chemically, alosetron is designated as 2,3,4,5-tetrahydro-5-methyl-2-[(5-methyl-1H-imidazol-4-yl)methyl]-1H-pyrido[4,3-b]indol-1-one,
monohydrochloride. Alosetron is achiral and has the empirical formula:
C17H18N4O HCl, representing a molecular
weight of 330.8. Alosetron is a white to beige solid that has a solubility
of 61 mg/mL in water, 42 mg/mL in 0.1 M hydrochloric acid, 0.3 mg/mL in
pH 6 phosphate buffer, and <0.1 mg/ mL in pH 8 phosphate buffer.
LOTRONEX Tablets for oral administration contain 1.124 mg alosetron HCl
equivalent to 1 mg of alosetron. Each tablet also contains the inactive
ingredients, lactose (anhydrous), magnesium stearate, microcrystalline
cellulose, and pregelatinized starch. The blue film-coat contains hydroxypropyl
methylcellulose, titanium dioxide, triacetin, and indigo carmine.