Cocrystals of Oxymatrine: Reducing Hygroscopicity and Affecting the Dissolution Rate

Oxymatrine (OMT) is mainly used for the treatment of hepatitis B. In this work, one anhydrous form and three hydrates of OMT are reported and their transformational relationship is clarified. It is revealed that OMT has high hygroscopicity and fast release characteristics. In order to improve these physical properties, cocrystallization of OMT was performed. Five cocrystals of OMT with urea (OMT-Urea-DH), sulfanilamide (OMT-SUA), theophylline (OMT-THP), 2-ketoglutaric acid (OMT-KTA-MH), and 3-hydroxy-2-naphthoic acid (OMT-HNA) were obtained and characterized. According to the DVS tests, OMT-SUA, OMT-KTA-MH, and OMT-HNA enhance the hydroscopic stability of OMT by forming new hydrogen bonds. The dissolution rate of OMT has been drastically reduced through cocrystallization with THP and HNA.