Mesalazine induced exacerbation of ulcerative colitis.

5-Aminosalicylic acid (5-ASA) compounds occasionally exacerbate diarrhoea in patients with inflammatory bowel disease. This is thought to be due to a secretory mechanism in most cases. A patient with presumed intolerance to sulphasalazine and 5-ASA preparations who developed endoscopic and histological evidence of disease relapse after a rectal challenge with mesalazine is reported.