The present disclosure relates to aqueous oral solutions comprising baclofen. In one embodiment, the aqueous oral solutions comprise a buffer comprising citric acid, a salt of citric acid, or any combination thereof, and are stored at from about 2° C. to about 8° C. The present disclosure also relates to buffer free aqueous oral solutions comprising baclofen. Additionally, the present disclosure relates to an assay for determining the amount of an impurity, 4-(3-carboxymethyl)-3-hydroxy-2,5-dioxopyrrolidin-1-yl)-3-(4-chlorophenyl)butanoic acid, in a baclofen containing solution, and to methods of treatment using such aqueous oral solutions.
