Zolpidem Phenyl-4-carboxylic acid is the major urinary metabolite of zolpidem, accounting for 51% of an administered dose. Literature references indicate the metabolite can be found in urine for 2-3 days following ingestion of a single therapeutic dose of zolpidem.1 Zolpidem, marketed as Ambien or Stilnox, is a nonbenzodiazepine used for the short-term treatment of insomnia.
1. J.H. Lewis and J.H. Vine. “A Simple and Rapid Method for the Identification of Zolpidem Carboxylic Acid in Urine.” Journal of Analytical Toxicology, Vol. 31, May 2007.