Flunarizine EP Impurity B DiHydrochloride

Flunarizine EP Impurity B Dihydrochloride is a piperazine-derived calcium channel blocker impurity characterized by a substituted phenylpiperazine core with a 2-(diphenylmethoxy)ethyl side chain. Its structure incorporates a fluorinated benzene ring and a dihydrochloride salt form, distinguishing it from the parent drug by the absence of the terminal ester functionality. This impurity arises via synthetic pathway deviations involving hydroxylation at the α-methylene position of the ethereal linkage. It serves as a critical HPLC reference standard for quantifying process-related impurities in flunarizine active pharmaceutical ingredient batches.