*3.7. Equilibrium Solubility*

As observed in the previous section, cocrystals were thermodynamically stable when suspended in water at room temperature. They did not transform to component phases or there is no evidence of phase transitions, suggesting that these phases have equal or lower solubility than the drug or coformer. The equilibrium solubility of the new FUR cocrystals was lower than that of FUR at pH 7.4. As seen in Table 4, cocrystals possess lower solubility than FUR. Although the differences in equilibrium solubility between FUR and the cocrystals were significant, interestingly, the extent of enhanced solubility of the multi-component solids is more significant than the solubility of the drug coformers.


**Table 4.** Equilibrium solubility of FUR and its cocrystals in water PBS pH 7.4.

<sup>a</sup> Reported solubility of ETZ at 27 ◦C: 0.03 mg/mL [47]. <sup>b</sup> Reported solubility of PRX at 37 ◦C: 0.0198 mg/mL [48].
