High solubility crystalline hydrates of Na and K furosemide salts

• Published in: CrystEngComm 2014-01, Vol.16 (22), p.4842-4852
• Main Authors: Rao Khandavilli, U. B., Gangavaram, Swarupa, Rajesh Goud, N., Cherukuvada, Suryanarayan, Raghavender, S., Nangia, Ashwini, Manjunatha, Sulur G., Nambiar, Sudhir, Pal, Sharmistha
• Format: Article
• Language: English
• Subjects: Crystallization; Differential scanning calorimetry; Diuretics; Drugs; Hydrates; Phase transformations; Sodium; Solubility
• ISSN: 1466-8033; 1466-8033
• DOI: 10.1039/C3CE42347F

Novel sodium and potassium salts of the poorly soluble loop diuretic drug furosemide were prepared with the intent of improving drug solubility and bioavailability. Furo–Na salt was obtained as a trihydrate upon crystallization from aqueous NaOH solution, and furo–K salt crystallized as a monohydrate from KOH solution. Both salt hydrates were characterized by X-ray diffraction, DSC, TGA, and IR spectroscopy. An exothermic phase transition at 165 °C in the DSC heating curve of the furo–Na salt indicates the likelihood of polymorphism in its anhydrate phase. Based on solubility studies, furo–Na–trihydrate and furo–K–monohydrate in pH 7 phosphate buffer medium exhibited significantly higher aqueous solubilities of 41 mg mL −1 and 106 mg mL −1 compared to the free drug (0.01 mg mL −1 ). The physical stability of these fast dissolving salts under accelerated ICH conditions of 40 °C and 75% RH was modest, with furo–Na salt being stable for 2 weeks and furo–K salt for 1 week.