Pharmacology of olsalazine

In the treatment of inflammatory bowel disease the main anti-inflammatory component of sulphasalazine is 5-ASA. Based on the same azo-splitting principle in the colon as sulphasalazine, the new drug olsalazine was developed. Olsalazine consists of two 5-ASA molecules joined by an azo bridge. Pharmacokinetic studies have shown that on oral administration there is little systemic absorption of olsalazine. Almost the whole dose passes into the colon, where the olsalazine is completely split into 5-ASA and subsequently excreted in faeces and urine. It can be concluded that from all toxicological and pharmacological aspects, olsalazine is a safe drug. Olsalazine will present the colonic mucosa with twice the amount of 5-ASA/unit compared with sulphasalazine (the present drug of choice) without concomitant delivery of sulphapyridine, which is believed to carry most of the drug's side-effects. Thus, olsalazine seems to be a suitable drug for long-term treatment of ulcerative colitis in man.