 Sulfasalazine has been a major agent in the therapy of mild to moderate ulcerative colitis for over 50 years.In 1977, it was shown that 5-aminosalicylic acid (5-ASA, mesalazine/mesalamine) was the therapeutically active component in sulfasalazine.Many 5-ASA drugs have been developed with the aim of delivering the active compound to the large intestine to maintain therapeutic efficacy but with reduction of the side effects associated with the sulfapyridine moiety in sulfasalazine.