Thermodynamics Study on Solubility Change in Injection Admixing and Preparation of the Incompatibility Estimation Table.

We examined the solubility change in injection admixing using thermodynamics. During our investigation, information regarding solubility, as described on the package insert, was utilized as reference data.The solubility of a compound in water is determined by the balance of the force which promotes dissolution and the force which prevents dissolution. Enthalpy of hydration, entropy of sublimation and dissociation are forces which all promote dissolution. Ionic lattice energy, entropy of hydration, Van der Waals force, and the generation of hydrophobic bond are forces which prevent dissolution. If the force which prevents dissolution is larger than the force which promotes dissolution, then a compound will not dissolve in water even if it is an ionic compound. Therefore, the generation of a hydrophobic bond and the aggregation of a polyvalent cation and polyvalent anion are considered to be important factors in the formation of insoluble ionic compounds.The incompatibility estimation table was prepared by classifying the injection formulation into six groups (anionic insoluble compound, anionic soluble compound, cationic insoluble compound, cationic soluble compound, nonionic insoluble compound, and noncationic nonanionic soluble compound). A rapid chemical evaluation of injection admixing is possible by using of the incompatibility estimation table.