Overcoming the Hydrophobic Nature of Zinc Phenylacetate Through Co-Crystallization with Isonicotinamide

Zinc phenylacetate (Zn-PA), a substitute for sodium phenylacetate as an ammonia-scavenging drug is hydrophobic, which poses problems for drug dissolution and solubility. We were able to co-crystallize the zinc phenylacetate with isonicotinamide (INAM) and produce a novel crystalline compound (Zn-PA-INAM). The single crystal of this new crystal was obtained, and its structure is reported here for the first time. Zn-PA-INAM was characterized computationally by ab initio, Hirshfeld calculations, CLP-PIXEL lattice energy calculation, and BFDH morphology analysis, and experimentally by PXRD, Sc-XRD, FTIR, DSC, and TGA analyses. Structural and vibrational analyses showed a major modification in intermolecular interaction of Zn-PA-INAM compared to Zn-PA. The dispersion-based pi-stacking in Zn-PA is replaced by coulomb-polarization effect of hydrogen bonds. As a result, Zn-PA-INAM is hydrophilic, improving the wettability and powder dissolution of the target compound in an aqueous solution. Morphology analysis revealed, unlike Zn-PA, Zn-PA-INAM has polar groups exposed on its prominent crystalline faces, reducing the hydrophobicity of the crystal. The shift in average water droplet contact angle from 128.1° (Zn-PA) to 27.1° (Zn-PA-INAM) is strong evidence of a marked decrease in hydrophobicity of the target compound. Finally, HPLC was used to obtain the dissolution profile and solubility of Zn-PA-INAM compared to Zn-PA.

Mechanistic study of the formation of arbutin polymorphs and solvates

Six solid forms of arbutin are successfully obtained and four single crystal structures are reported for the first time. Further, the formation mechanism of arbutin solvates is proposed and rationalized.

Stable Fatty Acid Solvates of Dasatinib, a Tyrosine Kinase Inhibitor: Prediction, Process, and Physicochemical Properties

Exploration of alternate solid forms for dasatinib, a potent oncogene tyrosine kinase inhibitor classified under Biopharmaceutics Classification System (BCS) class II drugs with low water solubility and high permeability, has been performed using COSMO-RS excess enthalpy (Hex) to increase dissolution. The theoretical prediction resulted in the potential for the formation of C₆-C₈ fatty acid solvates with dasatinib. A crystallization process has been identified for the preparation of the predicted solvates and successfully scaled up till the 100 g level. The fatty acid solvates are completely characterized using powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier transform infrared (FT-IR) spectroscopy, and proton nuclear magnetic resonance (¹H NMR) spectroscopy. Unique powder X-ray diffraction patterns and powder indexing of C₆-C₈ fatty acid solvates indicate the purity of the solid phase. The red shift in the acid carbonyl stretching frequency of C₆-C₈ fatty acids in FT-IR spectra and the intactness of the fatty acid proton in ¹H-NMR spectra provide evidence for solvate formation. The stoichiometry of active pharmaceutical ingredients (APIs) with solvent in solvates is measured using TGA and ¹H-NMR spectroscopy. Dasatinib C₆-C₈ fatty acid solvates were found to retain their solid form under various stress and pharmaceutical processing conditions. In addition, they exhibited improved powder dissolution over dasatinib Form H1-7 by 2.2-fold. They also showed stability at 40 °C and 75% RH for 3 months. C₈ fatty acid is a USFDA GRAS listed solvent, and hence may be a viable option for drug product development.

Mechanochemical Synthesis and Physicochemical Characterization of Previously Unreported Praziquantel Solvates with 2-Pyrrolidone and Acetic Acid

Two new solvates of the widely used anthelminthic Praziquantel (PZQ) were obtained through mechanochemical screening with different liquid additives. Specifically, 2-pyrrolidone and acetic acid gave solvates with 1:1 stoichiometry (PZQ-AA and PZQ-2P, respectively). A wide-ranging characterization of the new solid forms was carried out by means of powder X-ray diffraction, differential scanning calorimetry, FT-IR, solid-state NMR and biopharmaceutical analyses (solubility and intrinsic dissolution studies). Besides, the crystal structures of the two new solvates were solved from their Synchrotron-PXRD pattern: the solvates are isostructural, with equivalent triclinic packing. In both structures acetic acid and 2-pyrrolidone showed a strong interaction with the PZQ molecule via hydrogen bond. Even though previous studies have shown that PZQ is conformationally flexible, the same syn conformation as the PZQ Form A of the C=O groups of the piperazinone-cyclohexylcarbonyl segment is involved in these two new solid forms. In terms of biopharmaceutical properties, PZQ-AA and PZQ-2P exhibited water solubility and intrinsic dissolution rate much greater than those of anhydrous Form A.

Hydrogen bonding from crystalline water mediates the hydration/dehydration of mequitazine glycolate

Comparison of crystal structures, dynamic vapor adsorption measurements, lattice energy calculations and structural optimization of the dehydration model were used to evaluate the hydration-dehydration behavior.