Ulcerative colitis patients with an inflammatory response upon mesalazine cannot be desensitized: a randomized study

BACKGROUND AND AIMS: Mesalazine is a key drug in the treatment of ulcerative colitis (UC). Intolerance to mesalazine has been described, including fever and gastrointestinal symptoms. Several case reports reported successful desensitization of patients with mesalazine intolerance. The aim was to assess the number of UC patients who are persistently intolerant to mesalazine after single-blinded rechallenge and to test the effectiveness of a rapid desensitization protocol in UC patients demonstrated mesalazine intolerance. METHODS: This is a prospective, single-blind randomized study in UC patients who discontinued mesalazine because of intolerance. Patients with severe reactions were excluded. Eligible patients underwent a skin patch test with mesalazine followed by a single-blinded randomized crossover rechallenge with 500 mg mesalazine or placebo. Patients with symptoms upon rechallenge were admitted to the hospital for 3 days oral desensitization. RESULTS: Nine of the 37 identified UC patients who discontinued mesalazine because of intolerance were included. All nine patients had negative patch tests, seven patients had symptoms (fever, nausea, vomiting and diarrhea) within 2 h upon rechallenge. Four of these seven patients participated in the desensitization protocol and in none a successful desensitization could be performed. All four had an inflammatory intolerance reaction with rise in C-reactive protein. There were no elevations in serum tryptase or urinary-methylhistamine levels observed and no signs of immediate type allergic reactions, like urticaria, bronchial obstruction or anaphylaxis. CONCLUSION: We recommend not to rechallenge UC patients with an inflammatory response upon mesalazine and these patients will not benefit from a rapid desensitization protocol.