A method for producing a drug substance of crystalline pitavastatin calcium excellent in stability, is presented. In the production of a compound (pitavastatin calcium) represented by the formula (1): The water content is adjusted to a level of from 5 to 15%, and the crystal form is controlled to be crystal form A, thereby to obtain a drug substance excellent in stability.在此提供一種安定性極佳的晶形匹伐他汀鈣(pitavastatin calcium)之藥物的製法。在製造以式(1)表示的化合物(匹伐他汀鈣)時:水含量係調整到5至15%之水準,並且晶型係控制至晶型A,由是製得安定性極佳的藥物。
