A stabilized pharmaceutical composition comprising a nonpeptidic pharmaceutically active ingredient having a primary or secondary amino group, an excipient and an acidic compound as stabilizer, wherein the nonpeptidic pharmaceutically active ingredient is a compound represented by the formula depicted herein, and the variables shown in the formula are as defined in the specification； wherein the excipient is selected from the group consisting of mannitol, croscarmellose sodium, hydroxypropylcellulose, hydroxypropylmethylcellulose, polyethylene glycol, polyvinylpyrrolidone, crystalline cellulose, lactose, sucrose, starch, cornstarch, titanium oxide (TiO2) and light anhydrous silicic acid； and wherein the acidic compound is an organic acid selected from the group consisting of adipic acid, ascorbic acid, benzoic acid, oleic acid, succinic acid, acetic acid, tartaric acid, sorbic acid, fumaric acid, lactic acid, maleic acid, malonic acid, citric acid, malic acid and a salt thereof.
