Cyclobenzaprine USP RC B (Nortriptyline Impurity B)

Cyclobenzaprine USP RC B (Nortriptyline Impurity B) is a structurally related impurity derived from the parent drug cyclobenzaprine through a demethylation process, featuring a 1-cyclohexyl-3,4-dihydro-1,5-benzodiazepine-2,4-dione scaffold with a chloro substituent at the 10-position and a desmethylated amine functionality. This compound retains the core benzodiazepine ring system but exhibits altered substituents at the nitrogen center, leading to distinct chromatographic and spectroscopic profiles. It serves as a critical HPLC reference standard for quantifying this specific degradation byproduct in cyclobenzaprine formulations.