Prediction of Compatibility of Intravenous Injection with Infusion Fluids Using Solubility Product

Abstract

In order to develop the intravenous injection of water-insoluble drugs, compatibility tests with infusion fluids, especially the occurrence of drug precipitate, were studied using the solubility product. A quinolone derivative (AT) was used as the water-insoluble drug. A lactic acid was selected for the optimal salt form. When the AT solution containing 0.006 _M lactic acid was admixed with a typical infusion fluid having a chloride ion, a hydrochloride salt was precipitated. The limit of precipitation yielded between 1.4 and 1.7×10^-5 Eq²/ι² as the ion product ([AT⁺][Cl^-]). This value agreed with the solubility product of the drug (Ksp), 1.62×10^-5 Eq²/ι². These results suggest that the limit of salt precipitate when a drug solution is admixed with infusion fluids can be estimated by the solubility product.