The physicochemical properties of digoxin.

In a study of variations in the physicochemical properties of digoxin powder from several commercial sources, recrystallizations of digoxin were performed under several conditions. Polymorphs were not obtained whereas a pure amorphous form was formed under certain conditions. The amorphous form was more soluble and more stable under compression than was the crystalline form; nevertheless in contact with water it crystallized quickly. Traces of the crystalline form reduced the dissolution rate and stability of the amorphous form. Variations in the thermal behaviour of commercial samples can be explained by the presence of variable proportions of the amorphous form and also by thermal decomposition that varies from one sample to another and generally occurs at 160 degrees C and above.