1979 年 99 巻 2 号 p. 141-145
Acebutolol hydrochloride was proved by thermal analysis (DTA and TG), IR spectra, and X-ray powder diffraction to have three crystalline forms (form I, II, and III) and an amorphous form. The amorphous form, which was stored at 20°under 91% R.H., was first transformed to forms II and III, and then it was finally transformed to form I. During this transformation, the incorporation and release of water were examined. Form I was stable at this condition, while form II was transformed to form I for 48 hr, and form III was transformed to form I for 2 hr. Further, it was found that the amorphous form was transformed to form II at 80°under 50% R.H. for 3 hr, but at 80°under vacuum it was transformed to form III. Form I at 138°for 8 hr and form III at 130°for 4 hr were transformed to form II. From these results it was concluded that form I was the most stable form at room temperature.