The aim of this study was to analyze the clinical efficacy and cytomorphologic changes of colon mucosa following the treatment of patients suffering from irritable bowel syndrome (IBS) with mesalazine (5-aminosalicylic acid [5-ASA]).

In this controlled, randomized, blind clinical trial, a total of 360 patients with varying subtypes of IBS were randomly treated with 500 mg of mesalazine qid or by standard therapy without mesalazine for a period of 28 days. Pre- and post-treatment pain intensity, pain duration, meteorism, stool abnormalities and endoscopic parameters were monitored, and biopsies or brush biopsies were examined histologically.

Treatment of IBS patients with mesalazine significantly reduced intensity and duration of pain in all subtypes of IBS, except for duration of pain in the subtype “undifferentiated”, where the difference was not significant. In addition, in patients with diarrhea type and undifferentiated type of IBS, mesalazine also significantly reduced the abnormal stool pattern. In comparison to the control group, administration of mesalazine reduced the incidence of endoscopic and cytomorphologic changes of the bowel mucosa, including changes in colon mucus, mucus production, cytologic or histologic parameters, epithelial cell degeneration, appearance of leukocytes and macrophages and cell infiltrations.

Mesalazine was effective in reducing several symptoms characteristic of IBS. It significantly reduced pain intensity and duration and improved cytohistologic parameters of the bowel mucosa.