Solubility determination and thermodynamic modelling of verapamil hydrochloride in methanol-water binary solvent systems from 293.15 K to 323.15 K

Verapamil Hydrochloride is a key calcium channel blocker used to treat cardiovascular disorders and prevent cluster headaches by inhibiting calcium influx, thus improving cardiovascular health. The solubility of Verapamil Hydrochloride (VH) in methanol + water binary solvent systems were studied using a gravimetric method at temperatures from 293.15 K to 323.15 K under atmospheric pressure. The solubility increased with temperature and methanol content, with the highest mole fraction solubility at a 0.90 methanol mole fraction and the lowest at 0.10. Various models, including Apelblat, Van't Hoff, modified Jouyban–Acree, and CNIBS/R-K, were used to calculate theoretical solubility, with RAD and RMSD assessing the model accuracy. Thermodynamic analysis indicated that VH dissolution is endothermic and entropy-driven. This data is valuable for optimizing VH purification and crystallization processes in the pharmaceutical industry.