Synthesis and structural characterization of two novel olanzapine cocrystals with decreased or enhanced dissolution rate

Olanzapine (OLZ) is a second-generation atypical anti-schizophrenia drug, and it had been developed into various formulations, including immediate release and long-acting formulations. Specific solubility properties of OLZ are very important to design formulations for specific administration. In present work, two novel cocrystals of OLZ were synthesized and characterized (OLZ-KAE·0.75EA·0.25H2O, OLZ-ORC, KAE = kaempferol, ORC = orcinol). Single crystal X-ray diffraction (SCXRD), powder X-ray diffraction (PXRD), synchronous thermal analysis and attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) were used to characterize the structure of the cocrystals. Hirshfeld surface analysis was used to understand intermolecular interactions in cocrystals. In OLZ-KAE·0.75EA·0.25H2O cocrystal, the ethyl acetate (EA) and H2O exist as channel crystalline solvate, and they can easily escape from the lattice channel. Powder dissolution study showed that OLZ-ORC improved the dissolution rate of OLZ in PH 6.8 phosphate buffer. However, OLZ-KAE·0.75EA·0.25H2O and its desolvation product decreased the dissolution rate of OLZ, and the release rate kept sustained and stable, which was very suitable for sustained release and long-acting muscle injection formulations.