Biorelevant Media to Simulate Fluids in the Ascending Colon of Humans and Their Usefulness in Predicting Intracolonic Drug Solubility

To develop media simulating human colonic fluids (HCFs), to evaluate their use in predicting intracolonic solubility of ketoconazole, danazol and felodipine and to compare solubilities in HCFs with previously determined solubilities in gastric (HGFs) and small intestinal (HIFs) fluids. Fasted state simulated colonic fluid (FaSSCoF) and fed state simulated colonic fluid (FeSSCoF) were designed to reflect fluids previously collected from the ascending colon in healthy adults. Solubilities of the three model compounds were determined in HCFs, simulated HCFs, and plain buffers. For ketoconazole, solubilities in FaSSCoF and FeSSCoF were closer than those in the corresponding plain buffers to the solubility in HCFs. For danazol and felodipine, solubilities in FaSSCoF and FeSSCoF predicted solubilities in HCFs. In the fasted state, solubilities of danazol and felodipine in HCFs were higher than or similar to in HGFs or HIFs, while the ketoconazole solubility was lower. In the fed state, solubilities of all three model compounds in HCFs were lower than in HGFs or HIFs. FaSSCoF and FeSSCoF more closely predict solubility of poorly soluble compounds in HCFs than plain buffers. In most cases, solubility in HCFs differs from those in HGFs and HIFs.