Therapeutic efficacy of sulfasalazine and its metabolites in patients with ulcerative colitis and Crohn's disease.

We studied the therapeutic efficacy of sulfasalazine and its metabolites sulfapyridine and 5-aminosalicylic acid in nine patients with Crohn's disease and in 23 patients with ulcerative colitis. In a randomized, controlled trial, we treated 11 patients for six weeks with 1 g of sulfasalazine three times a day, seven patients with 0.5 g of sulfapyridine three times a day, and 14 patients with 0.5 g of 5-aminosalicylic acid suppositories three times a day. The clinical state of the disease was characterized by an activity index, quality of stool, and remission rate. In addition, we monitored plasma levels of sulfapyridine, 5-aminosalicylic acid, and their acetylated metabolites. The initial activity index (mean +/- S.D.) was significantly reduced by sulfasalazine (from 245 +/- 129 to 100 +/- 71; P < 0.001) and by 5-aminosalicylic acid (from 251 +/- 65 to 90 +/- 93; P < 0.0001), but sulfapyridine was without benefit. Stool quality was also improved by sulfasalazine (82 per cent of the cases) and by 5-aminosalicylic acid (79 per cent). The highest remission rate was achieved with 5-aminosalicylic acid (86 per cent), followed by sulfasalazine (64 per cent) and sulfapyridine (14 per cent). Our investigations show that 5-aminosalicylic acid is the active moiety of sulfasalazine and that this effective metabolite may be an alternative to sulfasalazine in inflammatory bowel disease.