PROBLEM TO BE SOLVED : To provide a stable liquid formulation of a 2-oxo-1-pyrrolidine derivative, a process of preparation thereof, and therapeutic uses thereof.SOLUTION : The invention provides an aqueous solution of a pharmaceutical compound being (2S)-2-[(4R)-2-oxo-4-propyl-pyrrolidin-1-yl]butanamide represented by the formula in the figure, which has a pH value between 4.5 and 6.5. The solution may be an injectable solution in which the amount of the pharmaceutical compound is in the range of 0.01 to 200 mg per ml. The solution may be an oral solution in which the amount of the pharmaceutical compound is in the range of 0.01 to 100 mg per ml.SELECTED DRAWING : NoneCOPYRIGHT : (C)2019, JPO&INPIT