Some folks that experience allergic reactions can be desensitized:
In mild to moderate cases of Crohn's disease, sulfasalazine therapy should be instituted gradually, initially 1 to 2 tablets (500 mg) daily and increased by 500 mg doses to 2 to 4 g daily. Sulfasalazine should be administered in four divided doses, with meals and with a light snack at night. Although there are numerous clinicians who advise dosages up to 12 g each day, I have found that the evidence of side-effects precludes this level of medication in most patients. Side-effects are often dose related, reflect serum sulfapyridine levels, which can be identified in individual patients and then used as a guide to the dosage of sulfasalazine. Nausea and headache, the earliest side-effects, can be alleviated by temporarily lowering the dosage. To avoid the development of upper gastrointestinal side- effects (heartburn, epigastric discomfort), the coated tablet (Azulfidine-EN) can be used. Such allergic manifestations as skin rashes and fevers are not uncommon, but do not constitute a contradiction to further usage of sulfasalazine. My colleague, Burton Korelitz, and I have demonstrated that approximately 90 percent of patients with Crohn's disease who have allergic reactions to sulfasalazine can be successfully desensitized. ****We use initial dosages of one-eighth to one-fourth tablet daily for one week, with subsequent doubling of dosages on a weekly basis until all patients reach therapeutic dosage. For example, we give one-fourth of a tablet daily for one week, then one-half tablet daily for one week, then one tablet daily for one week, and so on. Approximately three of four patients have shown clinical improvement following desensitization. Additional information on desensitization is provided in the chapter on ulcerative colitis therapy.****