Oral fluid (OF) is an increasingly accepted matrix for drug testing programs, but questions remain about its usefulness for monitoring cannabinoids. Expectorated OF specimens (n=360) were obtained from 10 adult daily cannabis smokers before, during, and after 37 20-mg oral Δ9-tetrahydrocannabinol (THC) doses over 9 days to characterize cannabinoid disposition in this matrix. Specimens were extracted and analyzed by gas chromatography– mass spectrometry with electron-impact ionization for THC, 11-hydroxy-THC, cannabidiol, and cannabinol, and negative chemical ionization for 11-nor-9-carboxy-THC (THCCOOH). Linear ranges for THC, 11-hydroxy-THC, and cannabidiol were 0.25–50 ng/mL; cannabinol 1–50 ng/mL; and THCCOOH 5–500 pg/mL. THCCOOH was the most prevalent analyte in 344 specimens (96.9%), with concentrations up to 1,390.3 pg/mL. 11-hydroxy-THC, cannabidiol, and cannabinol were detected in 1, 1, and 3 specimens, respectively. THC was detected in only 13.8% of specimens. The highest THC concentrations were obtained at admission (median 1.4 ng/mL, range 0.3–113.6) from previously self-administered smoked cannabis. A total of 2.5 and 3.7% of specimens were THC-positive at the recommended Substance Abuse and Mental Health Services Administration (2 ng/mL) and Driving Under the Influence of Drugs, Alcohol and Medicines (DRUID) (1 ng/mL) confirmation cutoffs, respectively. THC is currently the only analyte for monitoring cannabis exposure in OF; however, these data indicate chronic therapeutic oral THC administration and illicit oral THC use are unlikely to be identified with current guidelines. Measurement of THCCOOH may improve the detection and interpretation of OF cannabinoid tests and minimize the possibility of OF contamination from passive inhalation of cannabis smoke.
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