A Five-Puff Cannabis Challenge Did Not Guarantee Identical Oral-Fluid THC Exposure

Oral-fluid cannabinoid concentrations after a five-puff smoking challenge varied with preceding oral THC treatment. Standardizing puff count did not demonstrate identical smoke deposition or absorbed dose.

A controlled but complex exposure history

Eleven frequent smokers completed oral THC medication periods with a smoking challenge on the fifth day. Daily oral doses ranged from placebo to 120 mg in divided doses. The study measured THC, CBN, CBD and metabolites in oral fluid rather than treating all cannabinoid measurements as one exposure marker.

The chemistry suggested a further question

After smoking, selected oral-fluid concentrations differed according to the preceding oral THC dose. The authors hypothesized that treatment-related tolerance changed smoking behavior and mucosal contamination. That was a proposed explanation, not a direct demonstration that puff volume or absorbed THC was identical or different in every participant.

Route and analyte were important

During oral dosing without new smoking, parent-cannabinoid concentrations generally declined, while oral-fluid THC-COOH was more responsive to the oral regimen. Parent THC in the mouth and a metabolite reflecting systemic processing therefore could not be interpreted interchangeably.

Do not count the reports as independent cohorts

This analysis and the related ad-libitum oral-fluid report came from the same 51-day research program. They address different phases and questions, not separate replications. Small sample size, prior smoking and the hypothesized topography mechanism limit inference. Neither a fixed puff count nor an oral-fluid concentration establishes an individual’s impairment, and the findings cannot be converted directly into a blood THC level.

Related analysis: oral-fluid sampling during the related ad-libitum smoking periods.

Primary research

Lee D; Vandrey R; Mendu DR; Anizan S; Milman G; Murray JA; Barnes AJ; Huestis MA. Oral fluid cannabinoids in chronic cannabis smokers during oral δ9-tetrahydrocannabinol therapy and smoked cannabis challenge. Clinical chemistry (2013). DOI: 10.1373/clinchem.2013.207316.