Solubility Studies of Amlodipine Besylate in Propylene Glycol plus Ethanol Mixtures at Different Temperatures

In this research, the solubility of amlodipine besylate was studied in the propylene glycol + ethanol mixtures at different temperatures (293.2-313.2 K). The study showed that the solubility increases with an increase in propylene glycol concentration, reaching its highest point at w1 = 0.8. Additionally, the solubility values have a positive correlation with temperature, which is typical for the solid solutes. The experimental solubility data were correlated with some well known cosolvency models and the accuracy of these models was investigated with the mean relative deviations (MRDs%) of the back-calculated data. MRDs were 1.2% for the van't Hoff model, 4.3 and 4.6% for the Jouyban-Acree and Jouyban-Acree-van't Hoff equations, 1.4% for the MRS model and 2.1% for the modified Wilson model. The apparent thermodynamic parameters (standard state Gibbs energy, enthalpy, and entropy) of dissolution of ADB in the non-aqueous saturated mixtures were also calculated with the van't Hoff and Gibbs equations at Thm = 303.0 K.