Prophylactic effects of olsalazine v sulphasalazine during 12 months maintenance treatment of ulcerative colitis. The Danish Olsalazine Study Group.

In a Danish multicentre trial we compared the relapse preventing effects of olsalazine and sulphasalazine in patients with ulcerative colitis over a 12 month treatment period. Two hundred and twenty seven patients (118 men) with at least two previous attacks of ulcerative colitis were randomly allocated according to a prearranged treatment schedule to olsalazine 500 mg bd or sulphasalazine 1 g bd in a double blind, double dummy fashion. One hundred and ninety seven patients completed the trial. The relapse rate after 12 month in the olsalazine group was 46.9% v 42.4% in the sulphasalazine group with a 95% confidence interval for the difference in proportions of -9% to 18%. Seven per cent of the patients were withdrawn from the trial because of adverse drug reactions and these were equally distributed between the two groups.