Famotidine EP Impurity B, chemically defined as 3,5-Bis[2-[[[2-[(diaminomethylidene)amino]thiazol-4-yl]methyl]sulfanyl]ethyl]-4H-1,2,4,6-thiatriazine 1,1-dioxide and designated Famotidine USP Related Compound B, is a symmetrical dimeric impurity of Famotidine, with molecular formula C₁₆H₂₃N₁₁O₂S₅ and molecular weight 561.74 g/mol. This impurity forms when two guanidinothiazolylmethylthio-propanimidamide units condense with a single sulfamoyl (sulfamide-derived) moiety during the final amidine-forming step, creating a central 4H-1,2,4,6-thiatriazine 1,1-dioxide ring that links two Famotidine-like side chains. It is therefore a key marker for controlling stoichiometry and condensation selectivity during API synthesis. Manufactured at Chemicea under precisely controlled synthetic and purification protocols, this reference standard is essential for impurity profiling, method validation (AMV), and quality-control testing in compliance with EP and USP requirements for Famotidine. Each batch is supplied with a comprehensive Certificate of Analysis supported by HPLC, ¹H-NMR, and Mass Spectrometry characterization data, ensuring dependable analytical traceability for regulatory submissions and ANDA filings. CAS No. 89268-62-2 | Explore complete technical documentation, Safety Data Sheet (SDS), and pricing.