Abstract: A stable pharmaceutical preparation containing an aminobenzenesulfonic acid derivative represented by the following formula (I) known as a therapeutic agent for cardiac insufficiency: or a salt thereof, or a hydrate thereof or a solvate thereof as an active ingredient, wherein each production of substance A having a retention time of about 6.4 minutes in a high performance liquid chromatography, substance B having a retention time of about 15.6 minutes in the high performance liquid chromatography, and substance C having about 22.8 minutes in the high performance liquid chromatography is substantially suppressed, wherein said high performance liquid chromatography is performed at a controlled flow rate for elution so as to give a retention time of about 7 minutes of said active ingredient by using an ultraviolet absorptiometer at 220 nm, an octylsilylated silica gel packed column (4 mm ×250 mm) at 40° C., and a mobile phase prepared by dissolving 7.

Abstract: The invention provides a medicament comprising a sialic acid derivative represented by the following formula and have superior solubility and absorbability. A solid dispersion comprising a water-soluble macromolecule such as hvdroxypropylmethylcellulose and a sialic acid derivative dispersed in the water-soluble macromolecule and represented by the following formula (I): [R1 represents a steroid compound residue; R2 represents hydrogen atom or a C1-C4 alkyl group, R3 represents a C1-C15 alkyl group etc.; X represents an oxygen atom or a sulfur atom], e.g., 3&agr;-[N-(5-acetamido-3,5-dideoxy-2-O-methyl-&agr;-D-glycero-D-galacto-2-noneuropyranosonyl)amino]cholestane.