Metabolic characteristics and risks of pharmaceutical excipient PEG400 revealed by a novel analytical strategy

Pharmaceutical excipient polyethylene glycol 400 (PEG400) is widely used in injections, nanotherapeutics, and drug delivery systems, yet its metabolic characteristics, pathways, and risks remain unclear. In this study, a novel analytical strategy based on ultra-high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UHPLC–Q-TOF/MS) was developed to comprehensively profile parent PEGs and metabolites. After PEG400 administration, 98 PEG metabolites of seven types were identified in rats. PEG undergoes two metabolic pathways: oxidative reactions, which generate PEG carboxylic acid, PEG aldehyde, and PEG formate ester; and conjugation reactions, which form three types of metabolites. Pharmacokinetics of parent PEGs and metabolites showed that the half-life of parent PEGs is molecular weight-dependent, and the most abundant metabolite, PEG–COOH, is rapidly formed. PEG and its metabolites were widely distributed in tissues, including kidneys, liver, and immune organs, and primarily excreted via the kidneys. Notably, this study first elucidated that PEG400 is oxidized via dual pathways of CYP enzymes and alcohol dehydrogenase/aldehyde dehydrogenase, indicating potential risks of excipient–drug interactions and disulfiram-like reactions. PEG acid metabolites can exacerbate nephrotoxicity in zebrafish and rats with acute kidney injury. These findings highlight unrecognized metabolic risks of PEG400 and raise safety concerns regarding its formulation development and clinical application.