Olsalazine-13C6is intended for use as an internal standard for the quantification of olsalazine by GC- or LC-MS. Olsalazine is an orally bioavailable prodrug form of the anti-inflammatory agent 5-aminosalicylic acid that is cleaved by bacterial azo reductases in the gut to generate active 5-ASA.1

In vitro, olsalazine increases ion transport in isolated rabbit distal ileum when applied to the luminal side (ED50= 0.3 mM) and stimulates fluid transport in rat jejunum when used at a concentration of 5 mM.2,3Olsalazine (150 mg/kg for 8 days) improves stool consistency and decreases occult and gross bleeding as well as myeloperoxidase (MPO) activity and leukotriene B4levels in colon tissue in a mouse model of acute colitis induced by dextran sulfate .4Olsalazine also inhibits bovine xanthine oxidasein vitro(IC50= 3.4 mg/L) and lowers serum uric acid levels in a mouse model of hyperuricemia induced by oxonic acid when administered at a dose of 20 mg/kg.5Formulations containing olsalazine have been used in the treatment of inflammatory bowel disease (IBD) and ulcerative colitis.