LAUSR

Abstract Drug solubility is an important characteristic affecting its bioavailability. The properties of ionic drugs affect their sensitivity to buffer composition. We aimed to elucidate the variations in ibuprofen solubility due to different buffers and buffer concentrations. We also examined the intermolecular interaction between IBP and lidocaine (LDC) in the presence or absence of phosphate ion to determine whether phosphate in buffer modifies IBP hydration and LDC hydrophobic hydration. The IBP/LDC mixture formed a complex in phosphate buffer, as confirmed by van't Hoff plot and diffusion-ordered NMR spectroscopy, where dissolving behavior changed from endothermic to an exothermic process. This behavior was only achieved in the presence of phosphate ion. We also examined the dependence of a drug’s solubility on the solubility of other drugs. Phosphate ion can greatly affect drug solubility behavior. This knowledge gives us to ensure comparative assessment that is suitable for the Electrolyte environment of patients.