The Erythromycin-N-Demethylase (ERND) Activity Assay Kit is designed for the quantitative measurement of ERND enzyme activity, primarily in liver microsomes, recombinant enzyme systems, or cell-based assays. ERND, commonly associated with cytochrome P450 enzymes such as CYP3A4, catalyzes the N-demethylation of erythromycin and related macrolide antibiotics, a critical step in their hepatic metabolism and clearance from the body. This assay kit is essential for pharmacokinetic and pharmacodynamic studies, assessing drug metabolism rates, enzyme kinetics, and substrate specificity. It is widely used in pharmaceutical research to evaluate potential drug-drug interactions, screen inhibitors of ERND activity, and support the development of safer therapeutics by understanding metabolic pathways in toxicology and biochemistry.