Disposition of 5-aminosalicylic acid by 5-aminosalicylic acid-delivering compounds.

Time-related urinary excretion and faecal excretion of 5-ASA and acetyl-5-ASA were measured in eight healthy volunteers after a single oral dose of the azo compounds sulphasalazine and olsalazine, the slow release compounds Pentasa, Asacol and Salofalk, and plain 5-ASA. After ingestion of both azo compounds and slow-release compounds, urinary excretion of 5-ASA was markedly delayed and reduced, and faecal excretion was enhanced. At all points of time, there was a significant, but not very marked difference in urinary excretion of 5-ASA after ingestion of the azo compounds and the slow-release compounds, in favour of the azo compounds. A significantly larger proportion of the ingested 5-ASA, moreover, was excreted in faeces after the intake of azo compounds as compared with slow-release compounds.