Mesalazine formulation intolerance due to suspected excipient allergy in the treatment of ulcerative colitis: a case report.

Mesalazine formulations are essential for treating ulcerative colitis (UC), and intolerance to these formulations complicates the treatment of this condition. Some cases of mesalazine formulation intolerance are caused by the excipients rather than the active ingredient mesalazine. Therefore, mesalazine administration can be continued in such cases by changing the mesalazine formulation. This report describes a case of intolerance to mesalazine in which UC was effectively treated by switching mesalazine formulations. A drug-induced lymphocyte stimulation test suggested that allergy to the additive povidone was the cause of mesalazine formulation intolerance. This is the first case study to identify an additive that caused mesalazine formulation intolerance.