*3.5. Thermal Analysis*

It is well accepted that the melting point of an API can be altered through cocrystallization [45]. The outcome will generally be a solid with a melting point between (M), lower (L), or higher (H) than the isolated API and coformer, following the occurrence trend M >> L > H [46]. The thermal behavior of the reported compounds was studied by DSC. In Figure 6, the DSC of the corresponding FUR–ETZ and FUR–PRX cocrystals are reported. Each trace shows one single endothermic event, which represents the melting point of these

pure species. Interestingly, while the melting point of the FUR–ETZ cocrystal (187.67 ◦C) is in between those of the reported for the two reference APIs (ETZ: 129–134 ◦C; FUR: 203–205 ◦C), FUR–PRX cocrystal shows a melting endotherm at 214.82 ◦C, higher than the melting point of its components (PRX: 201.89 ◦C; FUR: 203–205 ◦C), an indication that this pharmaceutical cocrystal is thermally more stable than FUR by itself. Although the density and packing coefficient of the cocrystals are similar (Table 1), the overall packing arrangement of FUR-PRX and the non-covalent interactions involved impact its thermal behavior.

**Figure 6.** Differential scanning calorimetry (DSC) plots of FUR–ETZ and FUR–PRX. Dotted lines correspond to the range of temperature reported for melting of FUR.
