Design of cocrystals for molecules with limited hydrogen bonding functionalities: propyphenazone as a model system

We report eight new cocrystals with an analgesic drug, propyphenazone, which belongs to a family of compounds that possess limited or no hydrogen bonding functionality. Such molecules present difficulties in predicting and selecting appropriate coformers for potential multicomponent systems, and current prediction methodologies are unsuitable due to their focus around hydrogen bonding. This study used a knowledge-based strategy to identify appropriate coformers as well as testing a wide variety of molecules to confirm the initial predictions. All new cocrystals were characterized using X-ray diffraction techniques as well as measuring their physiochemical properties. These included the thermal behavior, stability under slurry and accelerated conditions, solubility and dissolution rate and were compared with the parent propyphenazone. It was found that while the stability of most of the cocrystals and propyphenazone was comparable, a cocrystal with hydroquinone showed an increase in both the solubility and dissolution rate of propyphenazone