Examining the robustness of a theophylline cocrystal during grinding with additives

Abstract

The robustness of theophylline-p-hydroxybenzoic acid cocrystal (TP·pHBA) while grinding with additives in the solid state was evaluated through a series of solvent-drop grinding experiments with coformers containing various functional groups. Powder X-ray diffraction was used to qualitatively analyse the powders after grinding and identify the species present. The TP·pHBA cocrystal was found to be robust in the presence of benzoic acid (BA), p-nitrobenzoic acid (pNBA), p-(N,N-dimethylamino)benzoic acid (dMABA), m-hydroxybenzoic acid (mHBA), p-nitrophenol (pNP), hydroquinone (HDQ) and benzamide (BZA), but it disintegrates in the presence of salicylic acid (SA), 3,5-dinitrobenzoic acid (dNBA), acetamide (ACA) and melamine (MLM).