Polymer-assisted cocrystallisation via hot melt extrusion (HME) facilitates the cocrystallisation process and increases cocrystal yield compared with the HME of neat cocrystal components. This makes it an attractive method for the single-step continuous synthesis of pharmaceutical cocrystals. The aim of this study is to understand the effect of semicrystalline (Poloxamer P407, PXM) or amorphous (Soluplus®, SOL) polymers on the cocrystallisation of model theophylline-nicotinamide (TP:NA, 1:1) cocrystal with significantly different melting temperatures of API (TP, m.p. = 271.4 °C) and coformer (NA, m.p. = 128.7 °C) in neat and matrix-assisted cocrystallisation via HME. Compared with the processing of neat cocrystal components, the addition of PXM led to formulation of TP:NA cocrystal embedded in the polymer matrix and increased the cocrystal formation efficiency. On the other hand, the co-processing of cocrystal components with SOL resulted in the formation of cocrystal embedded in the amorphous polymer matrix or in the partially amorphous TP:NA/SOL composites. The one-step formulation of API:coformer mixtures with polymers using HME may result in phase changes or the formation of amorphous solid dispersions, which highlights the importance of matrix selection and phase control of the final product.
Keywords: Cocrystal; Cocrystal yield; Cocrystallisation; Hot melt extrusion; Mechanochemistry.
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