[Induction of tolerance in hypersensitivity to mesalazine (5-ASA)]

Mesalazine is a derivative of 5-aminosalicylic acid (5-ASA), which is useful in the treatment of intestinal inflammatory disease. Sulfasalazine is formed by two parts, sulfapyridine and 5-ASA, the latter being the active part of the molecule. The new preparatives derived from 5-ASA were developed in an attempt to avoid the traditionally associated side effects to sulfapyridine, although they are still observed and new effects appear. We present two cases. The first is a man diagnosed of inflammatory intestinal disease, with background of two previous reactions of urticaria and angioedema after acetyl salicylic acid, who presented urticaria after taking mesalazine. The second one had generalized urticaria after three months of initiating treatment with mesalazine. Given the need for treatment in both cases, a desensitization protocol to mesalazine was made. It was developed in 17 days in our service. Tolerance to that drug to therapeutic doses is reached. When faced with patients with hypersensitivity to different drugs, that are necessary to treat their disease, "desensitization" regimes, that assure good tolerance, can be made.