The subject invention provides pharmaceutical compositions containing laquinimod or a pharmaceutically acceptable salt thereof, an isolated compound of N-ethyl-4-hydroxyl-1-methyl-5-(methyl(2,3,4,5,6-pentahydroxyhexyl)amino)-2-oxo-N-phenyl-1,2-dihydroquinoline-3-carboxamide or a salt thereof, compositions containing N-ethyl-4-hydroxyl-1-methyl-5-(methyl(2,3,4,5,6-pentahydroxyhexyl)amino)-2-oxo-N-phenyl-1,2-dihydroquinoline-3-carboxamide and methods of preparing the same.