Development and validation of an enzyme immunoassay screen and achiral/chiral LC-MS/MS confirmation methods for...

Ketamine has legitimate medical use in the clinic as an analgesic, with the additional recent approval of the single ketamine isomer, (S)-ketamine/esketamine, as a therapy for treatment resistant depression. Unfortunately, ketamine is also prone to non-medical use, often as a club or party drug. Herein, we describe the development and validation of a ketamine enzyme immunoassay screen, and both achiral and chiral LC-MS/MS confirmation methods. Our screen cutoff was set at 500 pg ketamine/mg hair. The confirmation cutoff, following an extended 90% ethanol wash and drug extraction, was set at 500 pg ketamine/mg hair, with the additional requirement of 50 pg norketamine metabolite/mg hair. Achiral method linearity was obtained from 10 to 5000 pg ketamine and norketamine/mg hair, chiral method linearity was obtained from 50 to 5000 pg (R)-ketamine and (S)-ketamine/mg hair. The LOD and LLOQ were set at 10 pg analyte/mg hair for the achiral method and 50 pg analyte/mg hair for the chiral method. The LC-MS/MS confirmation method was applied to the analysis of n = 18 authentic hair samples containing ketamine from the United States workplace drug testing population.