Characterization of the complexes of furosemide with 2-hydroxypropyl-β-cyclodextrin and sulfobutyl ether-7-β-cyclodextrin

The purpose of this study was to prepare and characterize complexes of furosemide with 2-hydroxypropyl-β-cyclodextrin (2-HP-β-CD) and sulfobutyl ether-7-β-cyclodextrin (SBE-7-β-CD). Solid complexes of furosemide with 2-HP-β-CD and SBE-7-β-CD were prepared by using both a freeze–drying and kneading method. Physical mixtures were prepared for comparison. The inclusion complexes were characterized by differential scanning calorimetry, X-ray diffractometry (XRD) and 1H nuclear magnetic resonance spectroscopy ( 1H-NMR). 1H-NMR, and especially the use of the two-dimensional ROESY spectrum, was used to determine the position of the furosemide molecule inside the cyclodextrin cavity. 1H-NMR studies showed that furosemide fit into the cyclodextrin torus cavity with its furane ring nearest to the primary hydroxyl side.