Co-crystal structures of furosemide:Urea and carbamazepine:Indomethacin determined from powder x-ray diffraction data

Abstract

Co-crystallization is a promising approach to improving both the solubility and the dissolution rate of active pharmaceutical ingredients. Crystal structure determination from powder diffraction data plays an important role in determining co-crystal structures, especially those generated by mechanochemical means. Here, two new structures of pharmaceutical interest are reported: A 1:1 co-crystal of furosemide with urea formed by liquid-assisted grinding and a second polymorphic form of a 1:1 co-crystal of carbamazepine with indomethacin, formed by solvent evaporation. Energy minimization using dispersion-corrected density functional theory was used in finalizing both structures. In the case of carbamazepine:indomethacin, this energy minimization step was essential in obtaining a satisfactory final Rietveld refinement.