The active THC metabolite 11-hydroxy-THC appeared in only four oral-fluid specimens in this experiment. Its exclusion from subsequent analyses reflected sparse findings in this matrix, not proof that participants produced no active metabolite.
What the laboratory observed
The randomized study compared swallowed THC, THC/CBD oromucosal spray and placebo in fourteen cannabis users. Oral-fluid 11-hydroxy-THC was detected in four specimens collected within an hour after Sativex, at concentrations no higher than 2.8 ng/mL. The assay’s quantification limit for that analyte was 0.5 ng/mL.
Because the findings were so limited, the investigators excluded 11-hydroxy-THC from further data analyses. Their principal oral-fluid comparisons focused on other cannabinoids.
A saliva nondetection is compartment-specific
Oral fluid and plasma have different cannabinoid distributions. Not finding an analyte above a saliva reporting limit cannot establish its absence in blood, brain or the body as a whole. It also cannot demonstrate that metabolism failed to occur after a documented THC administration.
What cannot be inferred
Four results do not validate a sensitive route-of-use classifier or an impairment threshold. The observations belong to this device, method, formulation and limited sampling period. If a forensic conclusion depends on active-metabolite exposure, identify the actual specimen tested and avoid replacing a missing blood measurement with a negative saliva finding.
Related reading: cannabinoid assay interpretation.
Research cited
Lee and colleagues (2012). Can oral fluid cannabinoid testing monitor medication compliance and/or cannabis smoking during oral THC and oromucosal Sativex administration?. DOI: 10.1016/j.drugalcdep.2012.10.011.
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