Patent ID: 7034159

Claim:
A process for the attainment of pure and stable form II of torsemide comprising the following steps: suspension of crude dried torsemide in 10 parts of deionised water, the addition of 48% potassium hydrate solution, slowly with stirring maintaining the temperature at 20–25° C., until obtaining complete solution and without exceeding pH 12.5, filtration of the solution thus obtained through 40 micron paper, gradual acidification of the filtrate thus obtained by stirring with 80% acetic acid preferably until reaching a pH of 5.3–5.7 maintaining the temperature at 20–25° C. during the addition, obtaining a suspension, stirring of the suspension for 30 minutes at a temperature of 20–25° C., suction filtration of the solid obtained and washing with water, drying of the solid in a dryer under vacuum at a temperature of 50° C.