Sulphasalazine was first produced nearly 50 years ago through the inspiration of a Swedish doctor, Dr Nanna Svartz. Later, in controlled trials, this compound was shown to reduce substantially the frequency of recurrent attacks of ulcerative colitis when used as long-term maintenance therapy. Studies into the metabolism of sulphasalazine have shown that, when taken orally, most of the ingested dose reaches the colon intact, and within the colonic lumen, bacteria split sulphasalazine into two breakdown products, sulphapyridine and 5-ASA. 5-ASA was shown to be the active therapeutic moiety while sulphapyridine served simply as a carrier. Olsalazine was developed to retain the property of sulphasalazine of reaching the colon intact, but also to liberate two molecules of 5-ASA with no residual carrier.