Profiling urinary metabolites of naproxen by liquid chromatography–electrospray mass spectrometry

Glucuronidation, an important metabolic process for the biotransformation of drugs into easily eliminable water-soluble detoxification products, can also lead to biologically active or toxic glucuronide conjugates.The present work describes a liquid chromatography–electrospray mass spectrometry (LC–ESI-MS) approach for the characterization of naproxen and O-6-desmethylnaproxen glucuronides. The method is fast and efficient and permitted to individuate α and β isomers of both naproxen and O-6-desmethylnaproxen glucuronides. The procedure could be potentially extended to the characterization of other drug metabolites.