Relapse-preventing effect and safety of sulfasalazine and olsalazine in patients with ulcerative colitis in remission: a prospective, double-blind, randomized multicenter study. The Ulcerative Colitis Multicenter Study Group.

Forty-nine patients with ulcerative colitis in remission were entered into a prospective, double-blind, multicenter trial comparing the relapse-preventing effect and safety of 4 g sulfasalazine and 2 g olsalazine daily during 48 wk. Of the 46 evaluable patients, 23 were assigned to sulfasalazine and 23 to olsalazine. Seven of 23 patients (30.4%) relapsed on sulfasalazine and six of 23 patients (26.1%) on olsalazine (95% confidence interval of the difference -22.0% to 30.3%). The relapse-free survival curves did not differ significantly at any time during the trial period. In both treatment groups, three patients dropped out because of adverse effects. Four patients on sulfasalazine and six patients on olsalazine experienced minor adverse effects. One patient on sulfasalazine had mild leukopenia, and four patients on sulfasalazine and one patient on olsalazine had decreased levels of haptoglobin. Thus, sulfasalazine and olsalazine are equally effective in maintaining remission of ulcerative colitis and are accompanied by a similar incidence of adverse effects.