Mucosal 5-aminosalicylic acid concentration inversely correlates with severity of colonic inflammation in patients with ulcerative colitis

Background and aim-The treatment of ulcerative colitis (UC) with 5-aminosal icylic acid (5-ASA) does not have the same therapeutic effect in all patien ts. We tested the hypothesis that the effectiveness of the drug is related to its mucosal concentration. Patients-Twenty one UC patients receiving oral 5-ASA (2.4-3.2 g/day) were e nrolled in the study. Four were also receiving topical treatment (2 g/day). Methods-Six endoscopic biopsies were taken from the rectum for measurement of 5-ASA concentrations (ng/mg) by HPLC; soluble interleukin 2 receptor (sI L-2R) concentrations (U/ml) were measured by ELISA and histology. Endoscopi c and histological appearance was graded on a four point scale (0-3). The W ilcoxon's rank test and Pearson's correlation coefficient were used for sta tistical analysis. Results-Mucosal concentrations of 5-ASA were significantly higher (p=0.03) in patients with endoscopic scores of 0-1 compared with those with scores o f 2-3 (16.1 (range 10.2-45) v 5.5 (3.5-17.4), respectively) and in patients with lower histological inflammation compared with those with more severe scores (17.4 (10.5-45) v 8.9 (3.5-17.2), respectively) (p<0.01). In contras t, mucosal sIL2-R concentrations were significantly lower in patients with slight endoscopic and histological lesions than in those with more severe d isease. A significative inverse correlation (r=-0.85) was found between 5-A SA and sIL-2R mucosal concentrations (p=0.00008). Conclusions-In patients with UC, in the same area of the intestinal tract, we found that the higher the 5-ASA mucosal concentrations, the lower the IL -2 R levels and endoscopic and histological scores. We hypothesise that mai ntenance of high mucosal 5-ASA concentrations in all colonic segments could contribute to improve clinical outcome in UC patients.