[Recent therapeutic modalities in chronic inflammatory bowel diseases: 4- or 5-aminosalicylic acid?]

In search of new therapies in IBD, the introduction of 4-aminosalicylic acid (4-ASA) has been proposed based on the longstanding, positive clinical experience in tuberculosis, the expected similar modes of action due to the close structural analogy to 5-aminosalicylic acid (5-ASA), an established therapy in IBD, and its inexpensiveness. To better understand the mechanisms of action of aminosalicylates, the intestinal inflammatory response and to develop new, more effective and cost saving drugs it is important to compare 4-ASA with 5-ASA with respect to their pharmacology, mechanisms of action and clinical efficacy. The inhibition of the upregulation of the initial local immune response, the inhibition of the production of inflammatory mediators, e.g. leukotrienes and the direct scavenging of toxic oxygen metabolites are important common antiinflammatory mechanisms. As the clinical experience with 4-ASA is promising, but still limited, 4-ASA currently cannot yet be recommended outside clinical trials. As the costs of 4-ASA are significantly lower compared to 5-ASA, 4-ASA may replace 5-ASA in the near future provided further trials will confirm the therapeutic and pharmacologic equivalency.