Isopropanol isopropyl acetate from

The solubility measurements of the two losartan forms (Form II prepared by heating) in isopropanol and ethyl acetate at 25 C and with overnight equilibration resulted in the conversion of Form U to Form I and no change in the initial Form I. The observed solubilities were 35 to 0.3 mg/g, respectively. However, in isopropyl acetate, no conversion of either form was observed after overnight equilibration at 25°C. The resulting solubihties were 18 and 41 mcg/gm for Forms I and II, respectively. More extensive solubility data, in methyl ethyl ketone at temperatures ranging from 25 to 65 C with shorter equilibration times that did not result in any conversions, showed Form I, once again, to have the lower measured values (Crocker and McCauley 1997). Extrapolation (Fig. 3-6) of the methyl ethyl ketone data indicated that the two solubility-temperature curves cross at a temperature of about 192 C, which is consistent with the enantiotropic transition seen in the DSC curves for Form I. The solubility data confirm that Form I is the more thermodynamically stable form at room temperature. 

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