Amorphism and physicochemical stability of spray-dried frusemide.

The physicochemical properties of amorphous forms of frusemide, prepared by spray-drying at 50 or 150 degrees C, and their hygroscopic stability at temperatures of 25 and 40 degrees C, and at 0 and 75% relative humidity were investigated. The glass transition temperature of the amorphous form A was 44.2 degrees C as measured by differential scanning calorimetry, while that of the amorphous form B was 54.4 degrees C. The activation energies for glass transition and crystallization processes were calculated from the differential scanning calorimetry thermograms of amorphous forms A and B, respectively. Stability determined by X-ray diffraction at 0% relative humidity, 25 and 40 degrees C suggested that form B was more stable than form A. However, the stability of form A at 75% relative humidity and 25 and 40 degrees C was similar to that of form B.