Polymorph selection of pharmaceutical cocrystals via bench-top and continuous production techniques

Abstract

Polymorphism can be a valuable tool as well as an impediment in the development and approval of pharmaceuticals, providing an opportunity to tune active pharmaceutical ingredient (API) physicochemical properties. The control of polymorphism in cocrystalline systems and other multicomponent forms remains underexplored. The study herein aims to investigate the potential of several techniques, liquid-assisted grinding (LAG), solvent evaporation (SE), supercritical enhanced atomization (SEA) and electrospraying, to control the cocrystal polymorphic outcome of three cocrystals: isonicotinamide-citric acid (IsoCa), ethenzamide-saccharin (EthSac) and ethenzamide-gentisic acid (EthGa). Solvent selection employing LAG and SE showed little effect on polymorphic outcome. Electrospraying and SEA primarily produced the α form of IsoCa, with process parameter variations leading to the β form during SEA, and a mixture of α and γ from electrospraying. Electrospraying led to the stable form I of EthSac, while SEA could produce pure form II, and a mixture. Electrospraying produced the form I of EthGa while SEA could produce form II, with an unknown polymorphic impurity. Density functional theory (DFT) computed electron density (ED) maps of cocrystal polymorph binary systems further rationalised the polymorphic predominance observed through the electrospraying. Ultimately this study provides a general road map for polymorph selection via atomization-based methodologies.