Low Plasma THC During High-CBD Oil Dosing Does Not Mean Zero Exposure
Most plasma THC measurements were below quantification during a controlled high-CBD oil study. That does not mean participants received no THC: the administered product contained THC, and the investigators also measured metabolites and urine outcomes.
A week of repeated dosing
Forty-three healthy adults were randomized among four active-dose groups and placebo. Daily doses ranged from 120 mg CBD with 5.4 mg THC to 480 mg CBD with 21.6 mg THC, administered in divided doses over seven days.
The trial assessed plasma and urine pharmacokinetics, adverse events and subjective effects. The formulation, dosing schedule and standardized meals were features of this experiment, not interchangeable details.
What the results support
CBD reached steady-state plasma conditions by day seven. Quantifiable parent THC in plasma was sporadic, with most concentrations below the assay’s 0.78 ng/mL quantification limit. No consistent subjective-effect differences separated active treatment from placebo across the assessed days.
Adverse events nevertheless occurred. Almost all were mild or moderate, and none was serious; three participants discontinued treatment because of events judged definitely or possibly related. Absence of a consistent subjective ‘high’ therefore was not absence of every treatment effect.
What should not be inferred
The groups were small and consisted of healthy volunteers. Subjective scales designed around abuse potential may not sensitively characterize every relevant CBD effect. The study did not validate driving fitness or demonstrate safety in patients taking interacting medications.
Below quantification means the assay could not reliably assign a numerical value under its criteria. It does not establish zero concentration at every time or erase known exposure from a documented dose.
Related analysis
See our discussion of equal labeled doses and different plasma profiles.
Primary research
Erica N Peters and colleagues. Safety, Pharmacokinetics and Pharmacodynamics of Spectrum Yellow Oil in Healthy Participants. Journal of Analytical Toxicology, 2021. DOI: 10.1093/jat/bkab026.
