Desensitization of patients with inflammatory bowel disease to sulfasalazine.

Seventeen patients with ulcerative colitis and three patients with Crohn's disease exhibited different side effects during sulfasalazine therapy. Eighty percent of these patients belonged to slow acetylator phenotypes. All side effects except skin rash were associated with a mean serum total sulfapyridine concentration of 62.9 +/- 17.4 micrograms/ml and free sulfapyridine concentration of 42 +/- 9.5 micrograms/ml. All patients were successfully desensitized, which allowed them the benefit of continued sulfasalazine therapy for prevention of relapses.