Montelukast

11 DESCRIPTION Montelukast sodium, USP the active ingredient in montelukast sodium tablets, is a selective and orally active leukotriene receptor antagonist that inhibits the cysteinyl leukotriene CysLT 1 receptor.‍‍‍‍‍‍​​​‍​​​​​​ Montelukast sodium, USP is described chemically as [R-(E)]-1-[[[1-[3-[2-(7-chloro-2-quinolinyl)ethenyl] phenyl]-3-[2-(1-hydroxy-1-methylethyl)phenyl] propyl]thio]methyl]cyclopropaneacetic acid, monosodium salt. The empirical formula is C 35 H 35 ClNNaO 3 S, and its molecular weight is 608.18. The structural formula is: Montelukast sodium, USP is a hygroscopic, optically active, white to off-white powder. Montelukast sodium is freely soluble in ethanol, methanol, and water and practically insoluble in acetonitrile. Each 10-mg film-coated montelukast sodium tablet, USP contains 10.4 mg montelukast sodium, USP which is equivalent to 10 mg of montelukast, and the following inactive ingredients: microcrystalline cellulose, lactose monohydrate, croscarmellose sodium, hydroxypropyl cellulose, disodium edetate and magnesium stearate. The film coating consists of: hydroxypropyl methylcellulose, hydroxypropyl cellulose, titanium dioxide, red ferric oxide and yellow ferric oxide. montelukast-structural