Characterization of the Contents of Ascending Colon to Which Drugs are Exposed After Oral Administration to Healthy Adults

To characterize the contents of the ascending colon in healthy adults under fasting and fed state conditions, with a view to designing in vitro studies to explain/predict dosage form performance in the lower gut. Twelve healthy adults participated in a two-phase crossover study. In Phase A, subjects were fasted (water allowed) overnight plus 5 h in the morning prior to colonoscopy (fasted state). In Phase B, subjects were fasted overnight, consumed a standard breakfast (960 kcal) in the morning, and were offered a light lunch 4.5 h later. In this phase, colonoscopy was performed 1 h after lunch (fed state). Volume, pH, and buffer capacity of colonic contents were measured immediately upon collection. After ultracentrifugation, the supernatant was further characterized. Free water content, pH, surface tension, and isobutyrate levels were lower in fed than in fasted subjects. On the other hand, buffer capacity, osmolality, acetate, butyrate, cholate, and chenodeoxycholate levels were higher in fed subjects. Carbohydrate content; protein content; and levels of long chain fatty acids, phosphatidylcholine, and cholesterol were not affected significantly by prandial state. Composition of fluids in the ascending colon is affected by feeding. This may affect the performance of products designed to deliver drug to the colon.