Thermodynamic analysis of atorvastatin calcium in solvent mixtures at several temperatures

Cosolvency is a widely used method employed to enhance drug solubility. There are limited data on the solubility of atorvastatin calcium (ATC). The aim of this work is to determine ATC solubility in glycerol + water and 2-propanol + water mixtures at several temperatures (293.15, 298.15, 303.15, 308.15 and 313.15 K). The apparent thermodynamic properties of the ATC dissolution process including Gibbs free energy (Delta G degrees(sol)), enthalpy (Delta H degrees(sol)) and entropy (Delta S degrees(sol)) were calculated. The ATC solubility in various concentrations of the anionic, cationic and non-ionic surfactant was explored. The drug is most efficiently dissolved in sodium lauryl sulphate (SLS). Tween 20 did not cause any increment in drug solubility. Benzalkonium chloride may form an insoluble salt with ATC anion resulting in a decrease in drug solubility. Cosolvency data were correlated by Jouyban-Acree and Jouyban-Acree-van't Hoff equation.