Formation thermodynamics of adefovir dipivoxil-saccharin co-crystals

Abstract

The solubilities of adefovir dipivoxil (AD) in saccharin (SAC) ethanolic solutions at different temperatures and in SAC aqueous solutions at constant temperature were determined to investigate the thermodynamic characteristics of AD-SAC co-crystals. The solubility products (Ksp), complexation constants (K11), and Gibbs free energy (ΔG°) were calculated. Ternary phase diagrams of the AD-SACethanol systems at various temperatures were established. We demonstrate that temperature has significant influence on the Ksp and K11 in ethanolic solution. Ksp decreased and K11 increased with a decrease in temperature. Dissolution of the co-crystals in ethanol is an endothermic process. Co-crystal formation is a spontaneous and endothermic process. A decrease in temperature favors complexation between the AD and SAC in ethanol. In aqueous solutions of SAC, the solubility of AD shows a threestage profile with a platform. © Editorial office of Acta Physico-Chimica Sinica.