A small percentage (about 3%) of patients with ulcerative colitis who are treated with mesalamine (5-ASA, 5-aminosalicylic acid) develop the acute intolerance syndrome with exacerbation of colitis symptoms.


A patient with an allergy to sulfasalazine or other sulfa compounds may be at increased risk for the syndrome.


Primary clinical features:

(1) abdominal cramping

(2) acute abdominal pain

(3) bloody diarrhea, which may be severe


Variable findings:

(1) fever

(2) headache

(3) malaise

(4) pruritis

(5) conjunctivitis

(6) skin rash


This needs to be distinguished from transient headache, nausea, dyspepsia, anorexia and other symptoms that respond to a dosage reduction or use of an enteric formulation.


Mesalamine therapy should be discontinued at the first sign of symptoms. Most patients improve on discontinuation of the mesalamine.


Rechallenge of the patient to mesalamine after an episode of acute intolerance may be hazardous and can precipitate life-threatening complications. It should only be attempted if absolutely necessary and with the patient under close, direct observation.


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