4-Ethoxy Nafcillin Sodium

4-Ethoxy Nafcillin Sodium is a structurally modified derivative of Nafcillin Sodium, featuring an ethoxy substituent at the 4-position of the benzyl side chain. This substitution introduces an ether linkage (–O–CH2CH3) adjacent to the beta-lactam ring, altering the compound's hydrophobicity and steric profile. The core structure retains the thiazolidine ring and carboxylate functionality characteristic of penicillin derivatives, while the sodium salt form ensures ionic stability. This impurity arises via alkylation of the parent drug under specific synthetic or degradation conditions, potentially impacting pharmacokinetic properties. It serves as a critical HPLC reference standard for quantifying process-related impurities in Nafcillin Sodium formulations.