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Herein, we report a new polymorph of amodiaquine dihydrochloride dihydrate obtained via heterogeneous crystallisation. This new polymorph exhibits similarity in molecular conformation as well as in its one-dimensional chain structure with a previously known polymorph, however with a difference in its two-dimensional sheet structure. Although crystal DFT-calculations predict the new form to be thermodynamically less stable compared to the previously known polymorph, the preparation method applied opened up the access to its metastable zone. [ABSTRACT FROM AUTHOR]

In this study, we attempt to simultaneously improve the photostability and solubility of epalrestat (a drug used for neuropathy treatment) by preparing epalrestat-betaine zwitterionic cocrystals and characterize the physicochemical property alterations accompanying their formation. Notably, we reveal that the strong hydrogen bonds between epalrestat and betaine molecules in the above cocrystals and the reduced size of the reaction cavity around epalrestat molecules prevent the E,Z to Z,Z photoisomerization of the latter, resulting in improved photostability. Furthermore, the prepared cocrystals exhibit a higher solubility and larger dissolution rate than pure epalrestat crystals due to featuring a layered structure with alternately arranged epalrestat and betaine coformer molecules. [ABSTRACT FROM AUTHOR]

Epalrestat, a drug for diabetic neuropathy, was able to form a cocrystal with a pharmaceutically acceptable coformer of caffeine. The cocrystal was characterized using powder X-ray diffraction and infrared spectroscopy, and the structure was determined using single crystal structure analysis. Pharmaceutically relevant physicochemical properties such as solubility, dissolution rate, and physical stability were evaluated. The cocrystal exhibited higher solubility and faster dissolution than the parent drug material. This improvement corresponded to the formation of a layered structure in the cocrystal, wherein a chain consisting of epalrestat molecules is sandwiched between caffeine molecules. The cocrystal also exhibited physical stability during a slurry experiment in most organic solvents, except in dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) solvents. In these solvents, the cocrystals underwent disproportionation into caffeine and epalrestat solvates (DMF and DMSO), and the crystal structures of epalerstat DMF and DMSO solvates are also reported in this study. [ABSTRACT FROM AUTHOR]