Famotidine EP Impurity F, chemically defined as 3-[[[2-[(Diaminomethylene)amino]thiazol-4-yl]methyl]sulfanyl]propanoic acid and designated Famotidine USP Related Compound F (Famotidine Propionic Acid), is a guanidinothiazole propanoic acid impurity of Famotidine, with molecular formula C₈H₁₂N₄O₂S₂ and molecular weight 260.33 g/mol. This impurity retains the guanidinothiazolylmethylthio scaffold of the parent H2-receptor antagonist but terminates in a carboxylic acid instead of the sulfamoyl amidine group. It is the end product of stepwise hydrolysis of the side chain (via the amide impurities C and D) during synthesis or storage. Given this pathway, the compound serves as a key reference marker for impurity profiling, hydrolytic degradation studies, and stability-indicating method development across Famotidine drug substance and formulation batches. 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, and is routinely applied in ANDA regulatory filings. 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 laboratories worldwide. CAS No. 107880-74-0 | Explore complete technical documentation, Safety Data Sheet (SDS), and pricing.