Solid-liquid equilibrium and thermodynamic properties of dipyridamole form II in pure solvents and mixture of (N-methyl pyrrolidone + isopropanol)

Abstract

The solid–liquid equilibria of a poorly soluble drug namely dipyridamole were assayed to determine solubility in pure and binary mixtures between 273.15 K and 313.15 K under atmospheric pressure. The solubility profiles of dipyridamole in pure and mixed solvents were evaluated by some thermodynamic models. The maximum solubility in mole fraction was obtained in pure N-methyl pyrrolidone (NMP) in all tested solvents. In mixtures of (NMP + isopropanol), the values increased monotonically with the increasing temperature and mass fraction of NMP. The Kamlet, Abboud and Taft Linear Solvation Energy Relationship (KAT-LSER) model was applied to analyze the effect of the solute–solvent intermolecular interactions on the solubility. The results of dissolution thermodynamic properties indicate that the dissolution behavior were endothermic and entropy-driven in all tested solvents. The experimental solubility data and mathematically correlated equations of dipyridamole estimated in this work may be useful for studies on the crystallization process of the final step of dipyridamole synthesis, for the purification dipyridamole of pharmaceutical applications.