One-step dry-coated tablets (OSDrC), which are useful as colon-targeting drugs, were prepared using Eudragit L 100-55 (Eud-L) and chitosan (Chit) as an outer layer. The lag time of OSDrC with an outer layer of Eud-L : Chit at a ratio of 3 : 1 in each test medium was greater than the gastric emptying time in the first fluid simulating the stomach and was greater than the small intestine transit time in phosphate buffer (pH 7.4) simulating the small intestine. Drug-release profiles of OSDrC were evaluated under test conditions considering the amount of gastric acid and bile acid, as well as the amount of fluid in the colon. The lag time of OSDrC was greater than the gastric emptying time in test medium simulating the stomach and greater than the small intestine transit time in test medium simulating the small intestine, although it was affected by the amount of gastric acid and bile acid. Drug release from OSDrC was completed within the colonic transit time in the test medium simulating the colon, although it was affected by the amount of fluid in the colon. Therefore the prepared OSDrC were found to permit drug delivery to the colon.
