Abstract:
The present work aims to understand the crystallographic basis of the mechanical behavior
of rivaroxaban-malonic acid cocrystal (RIV-MAL Co) in comparison to its parent constituents, i.e.,
rivaroxaban (RIV) and malonic acid (MAL). The mechanical behavior was evaluated at the bulk
level by performing “out of die” bulk compaction and at the particle level by nanoindentation.
The tabletability order for the three solids was MAL < RIV < RIV-MAL Co. MAL demonstrated
“lower” tabletability because of its lower plasticity, despite it having reasonably good bonding strength
(BS). The absence of a slip plane and “intermediate” BS contributed to this behavior. The “intermediate”
tabletability of RIV was primarily attributed to the differential surface topologies of the slip planes.
The presence of a primary slip plane (0 1 1) with flat-layered topology can favor the plastic deformation
of RIV, whereas the corrugated topology of secondary slip planes (1 0 2) could adversely affect the
plasticity. In addition, the higher elastic recovery of RIV crystal also contributed to its tabletability.
The significantly “higher” tabletability of RIV-MAL Co among the three molecular solids was the
result of its higher plasticity and BS. Flat-layered topology slip across the (0 0 1) plane, the higher
degree of intermolecular interactions, and the larger separation between adjacent crystallographic
layers contributed to improved mechanical behavior of RIV-MAL Co. Interestingly, a particle level
deformation parameter H/E (i.e., ratio of mechanical hardness H to elastic modulus E) was found to
inversely correlate with a bulk level deformation parameter σ0 (i.e., tensile strength at zero porosity).
The present study highlighted the role of cocrystal crystallographic properties in improving the
tabletability of materials.
