Use of Rectal Dialysis Technique to Measure Rectal 5-ASA Levels in Healthy Volunteers Receiving Asacol

Asacol® is mesalazine in a pH‐dependent tablet (Eudragit S) that remains intact until reaching the terminal ileum. The tablet dissolves at a pH 7 or greater, allowing mesalazine release in the terminal ileum and throughout the colon; hence, it would be anticipated that this form of 5‐ASA will produce higher concentrations in the left colon in patients with active ulcerative colitis compared to other immediate release forms of 5‐ASA. However, preliminary research using dynamic computer modeling and simulation predicted that patients with active ulcerative colitis (characterized by an increased stool frequency) treated with Asacol® and Lialda (another delayed release formulation) will achieve very low 5‐ASA levels in the sigmoid colon and rectum. The model predicts that these 5‐ASA preparations will be relatively ineffective in treating the left side of the colon in active ulcerative colitis.