Synthesis and Characterization of Metabolites and Potential Impurities of Balsalazide Disodium, an Anti-Inflammatory Drug

Balsalazide disodium (Colazide®) is an oral prodrug of mesalamine (5-aminosalicylic acid) and possesses anti-inflammatory properties. During the process development for balsalazide disodium, we observed eight impurities, namely des-β-alanine balsalazide, balsalazide β-alanine, balsalazide 3-isomer, decarboxy balsalazide, bis-azo salicylic acid, biphenyl-azo salicylic acid, bis-azo diacid, and bis-azo triacid. The present work describes the synthesis and characterization of these impurities.