Exceptional Powder Tabletability of Elastically Flexible Crystals

Abstract

Reversible elastic deformation is deleterious to tablet formation by powder compaction. However, highly elastic caffeine and 4-chloro-3-nitrobenzoic acid cocrystal methanolate (CCM) exhibited surprisingly high tabletability, surpassing that of well-known plastically deformable crystals. We show that the exceptional tabletability of CCM powder is due to the activation of the (010) slip planes along the <001> direction during tableting. The same slip system is dormant when the needle-shaped CCM single crystals are bent on the side faces (11̅0) or (110). Thus, the successful prediction of tableting performance requires consideration of crystal anisotropy and stress conditions during powder compression instead of the qualitative single-crystal bending behavior.