Oral fluid/plasma cannabinoid ratios following controlled oral THC and smoked cannabis administration

Dayong Lee, Ryan Vandrey, Garry Milman, Mateus Bergamaschi, Damodara R. Mendu, Jeannie A. Murray, Allan J. Barnes, Marilyn A. Huestis

Research output: Contribution to journalArticlepeer-review

22 Scopus citations


Oral fluid (OF) is a valuable biological alternative for clinical and forensic drug testing. Evaluating OF to plasma (OF/P) cannabinoid ratios provides important pharmacokinetic data on the disposition of drug and factors influencing partition between matrices. Eleven chronic cannabis smokers resided on a closed research unit for 51 days. There were four 5-day sessions of 0, 30, 60, and 120 mg oral â̂†9-tetrahydrocannabinol (THC)/day followed by a five-puff smoked cannabis challenge on Day 5. Each session was separated by 9 days ad libitum cannabis smoking. OF and plasma specimens were analyzed for THC and metabolites. During ad libitum smoking, OF/P THC ratios were high (median, 6.1; range, 0.2-348.5) within 1 h after last smoking, decreasing to 0.1-20.7 (median, 2.1) by 13.0-17.1 h. OF/P THC ratios also decreased during 5-days oral THC dosing, and after the smoked cannabis challenge, median OF/P THC ratios decreased from 1.4 to 5.5 (0.04-245.6) at 0.25 h to 0.12 to 0.17 (0.04-5.1) at 10.5 h post-smoking. In other studies, longer exposure to more potent cannabis smoke and oromucosal cannabis spray was associated with increased OF/P THC peak ratios. Median OF/P 11-nor-9-carboxy-THC (THCCOOH) ratios were 0.3-2.5 (range, 0.1-14.7) ng/μg, much more consistent in various dosing conditions over time. OF/P THC, but not THCCOOH, ratios were significantly influenced by oral cavity contamination after smoking or oromucosal spray of cannabinoid products, followed by time-dependent decreases. Establishing relationships between OF and plasma cannabinoid concentrations is essential for making inferences of impairment or other clinical outcomes from OF concentrations.

Original languageEnglish (US)
Pages (from-to)7269-7279
Number of pages11
JournalAnalytical and Bioanalytical Chemistry
Issue number23
StatePublished - Sep 2013


  • Cannabis
  • Delta9-tetrahydrocannabinol
  • Marijuana
  • Oral fluid
  • Plasma
  • Ratio

ASJC Scopus subject areas

  • Analytical Chemistry
  • Biochemistry


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