OBJECTIVES AND METHODSThe aim of this multicentre, randomized open trial was to compare the efficacy and tolerance of 4-ASA vs 5-ASA enemas in the treatment of distal moderately active ulcerative colitis. Fifty patients were randomized to receive enemas in 100 mL suspension of 4-ASA (2 g, n = 26), or 5-ASA (1 g, n = 24). The subjects filled a daily questionnaire on enema retention duration, and tolerance. Clinical and endoscopic evaluations were performed at baseline and after 2 and 4 weeks.RESULTSSignificant clinical and endoscopic improvements occurred in both groups. Efficacy and enema retention time did not differ between groups. Tolerance was significantly better for 4-ASA: score 0.46 +/- 0.77 vs 1.00 +/- 0.73, P = 0.03.CONCLUSIONSEfficacy of both treatments was equivalent, but 4-ASA enemas were better tolerated than 5-ASA in this open trial.