Carbamazepine (CBZ), a widely used antiepileptic, is known to be sensitive to light. The aim of this study was to evaluate the photostabilities of three cocrystals of CBZ (CBZ-succinic acid (SUC), CBZ-saccharin (SAC) form I, and CBZ-SAC form II) illuminated with a D 65 fluorescent lamp compared with those of the conventional solid forms: CBZ polymorphs (forms I, II, and III). The order of discoloration determined using a colorimetric measurement was almost consistent with that of the degradation rates estimated using Fourier-transform infrared reflection-absorption spectroscopy, and these parameters of CBZ polymorphs increased in the order of form III, form I, and form II. CBZ-SUC and CBZ-SAC form I significantly suppressed the discoloration and degradation of CBZ compared with the raw CBZ, while CBZ-SAC form II facilitated the discoloration and degradation of CBZ. These results were supported by the results from the low-frequency Raman spectroscopy. The molecular mobility estimated using solid-state nuclear magnetic resonance 1 H spin-lattice relaxation time strongly correlated with the degradation rate constant, indicating that molecular mobility significantly decreased following the formation of CBZ-SUC and CBZ-SAC form I and resulted in higher photostability. Overall, CBZ-SUC and CBZ-SAC form I are photostable forms and cocrystallization was proven to be an effective approach to improving the photostability of a photolabile drug.
We found a novel cocrystal consisting of captopril, which is an amino acid-derived drug having a thiol group, and l-proline by using nano-spot-screening with LF-Raman. This cocrystal hydrate showed high hygroscopicity resulted from changes in intermolecular interactions.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.