Theoretical modeling and prediction of biorelevant solubility of poorly soluble pharmaceuticals

The solubility of active pharmaceutical ingredients (APIs) in biorelevant media is important fundamental data for API formulation design and contributes to better evaluation of in vivo dissolution kinetics. However, these data are mainly determined by experimental measurements, which is rather time and cost consuming. Therefore, it is essential to develop a novel theoretical strategy to describe and predict API solubility in biorelevant media. In this work, the solubilization effect of micelle and the effect of pH as well as ion components on the solubility of naproxen and indomethacin were determined experimentally. A micellar solubilization model and pH-dependent solubility model were proposed to model the effect of various micelles and pH (including buffer components) on API aqueous solubility, respectively. The combination of the two model successfully described the biorelevant solubility of APIs as function of temperature. The proposed strategy could provide insights into the mechanisms of micelle and different pH regulated by different buffer components on API solubility and could accurately describe the solubility of APIs in biorelevant media. This work is expected to provide theoretical guidance for API formulation development.