Abstract
Anhydrous digoxin, digoxin · 1 4 H 2 O and digoxin · 1 2 H 2 O were characterized using X-ray powder diffractometry, diffuse reflectance Fourier transform infrared spectroscopy, intrinsic dissolution rates and scanning electron microscopy. X-ray powder diffraction patterns for the different forms showed small differences in the D values and intensities; differences were found in the ratio of the diffraction bands at 2θ ≈ 16.7, 17.9 and 14.6°. FTIR positions were the same for the different forms. Initial dissolution rates were in the order of anhydrous ⪢ digoxin · 1 4 H 2 O ⪢ digoxin · 1 2 H 2 O ; both anhydrous digoxin and digoxin · 1 4 H 2 O converted to the hemihydrate over a period of 2 h. There is evidence that at least one higher hydrate of digoxin exists. Digoxin · 1 4 H 2 O consisted mainly of thin plates and digoxin · 1 2 H 2 O was relatively large crystals arranged in clusters as seen on SEM photomicrographs.
Published Version
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