Famotidine EP Impurity E, chemically defined as 2,2′-[Disulfanediylbis(methylenethiazole-4,2-diyl)]diguanidine and designated Famotidine USP Related Compound E, is a symmetrical disulfide-linked dimeric impurity of Famotidine, with molecular formula C₁₀H₁₄N₈S₄ and molecular weight 374.52 g/mol. Structurally, this bis(guanidinothiazole) impurity forms through oxidative coupling of two molecules of the thiol intermediate (2-guanidinothiazol-4-yl)methanethiol, which can be released by hydrolysis of the isothiourea intermediate (Famotidine EP Impurity H) during synthesis. It is therefore a well-recognized marker for monitoring oxidation control and intermediate quality in Famotidine API manufacturing. Owing to this formation pathway, the compound plays a key analytical role in impurity profiling, oxidative stress studies, and stability-indicating HPLC method development for the parent H2-receptor antagonist. Manufactured at Chemicea under tightly controlled synthetic and purification protocols, this reference standard supports method validation (AMV) and quality-control testing in accordance with EP and USP monograph requirements for Famotidine, and is routinely applied in ANDA and DMF regulatory submissions. 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 laboratories worldwide. CAS No. 129083-44-9 | Explore complete technical documentation, Safety Data Sheet (SDS), and pricing.