Oral fluid (OF) is an accepted alternative biological matrix for drug treatment, workplace, and DUID (driving under the influence of drugs) investigations, but establishing the cannabinoid OF detection window and concentration cutoff criteria are important. Cannabinoid concentrations were quantified in OF from chronic, daily cannabis smokers during monitored abstinence. Delta(9)-tetrahydrocannabinol (THC)(3), cannabidiol (CBD), cannabinol (CBN), and 11-nor-9-carboxy-THC (THCCOOH) were determined in daily OF samples collected with the Quantisal™ device. GC-MS limits of quantification (LOQ) were 0.5 µg/L for THC and CBD, 1 µug/L for CBN, and 7.5 µg/L for THCCOOH. After providing written informed consent for this institutional review board–approved study, 28 par-ticipants resided from 4 to 33 days on the secure research unit and provided 577 OF specimens. At the LOQ, THC was generally quantifiable for 48 h, whereas CBD and CBN were detected only at admission. Median THCCOOH detection time was 13 days (CI 6.4 – 19.6 days). Mean THC detection rates decreased from 89.3% at admission to 17.9% after 48 h, whereas THCCOOH gradually decreased from 89.3% to 64.3% within 4 days. Criteria of THC [more or equal] 2 µg/L and THCCOOH [more or equal] 20 ng/L reduced detection to < 48h in chronic cannabis smokers. An OF THCCOOH/THC ratio [smaller or equal] 4 ng/µg or presence of CBD or CBN may indicate more recent smoking. THC, THCCOOH, CBD, and CBN quantification in confirmatory OF cannabinoid testing is recommended. Inclusion of multiple cannabinoid cutoffs accounted for residual cannabinoid excretion in OF from chronic, daily cannabis smokers and could reduce the potential for positive test results from pas-sive cannabis smoke exposure and lead to greatly im-proved test interpretation. (Author/publisher)
Abstract