A retrospective review of phencyclidine in hair samples of subjects from the United States workplace drug testing population

The dissociative anesthetic phencyclidine (PCP) remains an encountered analyte in typical routine testing in forensic toxicology. Herein, we describe a validated GC/MS method for PCP measurement in subjects using human head and body hair with a limit of detection (LOD) of 100 pg PCP/mg hair, with method linearity established from 100 to 15,000 pg PCP/mg hair. The GC/MS method was used to analyze samples from the United States workplace drug testing population (n = 368 samples) containing PCP over the years 2021 to 2025. The statistical comparison of PCP median concentrations for samples reported as black or brown in color, or samples collected using head or body hair, found no significant median concentration difference in either case. Many of the samples (65%) had the concurrent presence of at least one additional drug other than PCP, with cocaine (50%), amphetamines (20%) and cannabinoids (18%) as the most commonly observed drug substances. With the exception of an increased median concentration in year 2021, annual PCP median hair concentrations over the time period of this manuscript were stable.