Review article: the mode of action of the aminosalicylates in inflammatory bowel disease.

Sulphasalazine and other 5-aminosalicylic acid (5-ASA)-containing drugs are used in the treatment of acute inflammatory bowel disease and in the maintenance of clinical remission. Despite their use for over 50 years, the mechanism of action of this class of drugs remains uncertain, although a number of possibilities are discussed in this review. It seems likely that the aminosalicylates are important free radical scavengers, can reduce leukotriene production and can inhibit the cellular release of interleukin-1, all of which are likely to be important in reducing the acute inflammatory response in inflammatory bowel disease. The effects of these drugs on prostaglandin production are more contentious, but it appears that 10(-5) to 10(-4) M concentrations stimulate production of prostaglandins which may be cytoprotective, while higher doses of these drugs inhibit prostaglandin production. The aminosalicylates may maintain remission in inflammatory bowel disease by preventing leucocyte recruitment into the bowel wall. The drugs inhibit the chemotactic response to leukotriene B4, reduce the synthesis of platelet activating factor and also inhibit leucocyte adhesion molecule upregulation.