Famotidine EP Impurity D, chemically defined as 3-[[[2-[(Diaminomethylene)amino]thiazol-4-yl]methyl]sulfanyl]propanamide and designated Famotidine USP Related Compound D (Famotidine Propanamide), is a guanidinothiazolyl-propanamide impurity of Famotidine, with molecular formula C₈H₁₃N₅OS₂ and molecular weight 259.35 g/mol. Structurally, this compound retains the guanidino-substituted thiazole core of the parent H2-receptor antagonist but terminates in a simple propanamide instead of the N-sulfamoylpropanimidamide group. It arises from hydrolysis of the propanenitrile/imidate intermediates during synthesis and from hydrolytic degradation of Famotidine itself, so it is monitored both as a process-related and a degradation impurity. This makes it a key reference marker for synthetic control, intermediate carryover, and stability monitoring across Famotidine API manufacturing. Manufactured at Chemicea under tightly controlled synthetic and purification protocols, this reference standard supports impurity identification, method validation (AMV), and quality-control testing in compliance 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 pharmaceutical R&D and QC laboratories. CAS No. 76824-16-3 | Explore complete technical documentation, Safety Data Sheet (SDS), and pricing.