Diclofenac EP Impurity A, chemically defined as 1-(2,6-Dichlorophenyl)-1,3-dihydro-2H-indol-2-one and also recognized as Diclofenac USP Related Compound A, Diclofenac Amide, or Diclofenac Lactam, is a cyclized oxindole (lactam) impurity of Diclofenac, with molecular formula C₁₄H₉Cl₂NO and molecular weight 278.13 g/mol. Structurally, this impurity forms through intramolecular dehydrative cyclization (lactamization) between the carboxylic acid side chain and the diarylamine nitrogen of Diclofenac, creating a five-membered oxindole ring; this reaction is favoured by heat and acidic conditions and is a known concern during heat sterilization of Diclofenac injectables. It is also the penultimate intermediate of the classical Diclofenac synthetic route. Given this dual process and degradation origin, the compound serves as a key reference marker for forced-degradation studies, stability-indicating method development, and cyclization-related impurity control across Diclofenac Sodium and Diclofenac Potassium manufacturing. Synthesized at Chemicea under precisely controlled reaction and purification protocols, this reference standard supports impurity identification, method validation (AMV), and quality-control testing in line with EP, BP, and USP monograph requirements, and is routinely applied in ANDA and DMF 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 regulatory and R&D laboratories. CAS No. 15362-40-0 | Explore complete technical documentation, Safety Data Sheet (SDS), and pricing.