Negative Morning Saliva Screens After Cannabis Oil Did Not Measure Driving Recovery
Negative oral-fluid screens the morning after a single THC/CBD oil dose established a testing outcome, not demonstrated driving recovery. The study also found poor screening sensitivity shortly after dosing despite measurable THC in some participants’ saliva.
One evening dose in adults with insomnia
Twenty adults with insomnia completed a blinded crossover comparison of placebo and an oral oil containing 10 mg THC plus 200 mg CBD. Oral fluid was tested before dosing and at 0.5, 10 and 18 hours.
DrugWipe 5S and DrugTest 5000 screening results were compared with laboratory LC–MS/MS measurements. Their stated screening cutoffs differed: 10 and 25 ng/mL THC, respectively. Device names alone therefore do not establish identical decision rules.
Early and later results answered different questions
At 30 minutes, oral-fluid THC ranged from zero to 425 ng/mL. Screening sensitivity was 25% for DrugWipe and 50% for DrugTest in the reported analysis. A negative screen shortly after use could therefore coexist with a reference-positive specimen.
At ten and 18 hours, all measured oral-fluid THC concentrations were below the screening cutoffs and all screens were negative. That finding describes one-off administration under this protocol; it does not establish the same probability after repeated medicinal use.
Do not replace a functional assessment with a detection window
Oral fluid may contain local product residue as well as cannabinoids entering through other pathways. Variation in administration and collection can affect results. A urine or blood result is also a different measurement.
The experiment evaluated chemical detection rather than whether a person could drive safely the following morning. Its practical contribution is to show that screening performance depends on elapsed time, product, route and cutoff. Both an early false negative and a later expected negative require that context.
Related: Interpreting cannabinoid concentrations and functional effects.
Primary research
Detection of Δ9‐tetrahydrocannabinol (THC) in oral fluid using two point‐of‐collection testing devices following oral administration of a THC and cannabidiol containing oil. Drug Testing and Analysis (2024).
