Cannabis edibles produced delayed, lower blood THC peaks than smoking, with women showing higher concentrations | Research

The takeaway

In 17 infrequent cannabis users eating THC brownies, blood THC peaked at 1.5-2 hours and returned to baseline within 8 hours, with women showing higher peak concentrations than men.

Forensic toxicologists, drug testing policy makers, and cannabis edible consumers.

Women: higher THC peaks; oral fluid detection immediate but not reflective of blood levels

What the researchers found

After consuming cannabis brownies (0, 10, 25, or 50 mg THC), blood THC and 11-OH-THC peaked at 1.5-2 hours and returned to baseline within 8 hours. THCCOOH and THCCOOH-glucuronide were higher than THC and persisted beyond 8 hours. Women had higher peak THC and metabolite concentrations, partly due to lower body weight/BMI. Oral fluid THC was detected immediately (oral deposition, not blood circulation) and was much higher than blood THC.

Why it matters

This is one of the few controlled studies with both sexes examining oral cannabis pharmacokinetics. The sex differences (higher THC in women) and oral fluid findings (immediate detection not reflecting blood levels) have direct implications for drug testing interpretation.

The numbers in context

17 subjects (8 female); THC peak 1.5-2h; baseline within 8h; women: higher peaks; oral fluid THC detected immediately; ELISA-LC/MS agreement >90% for blood THCCOOH and oral fluid THC, but 67% for oral fluid THCCOOH.

How the study worked

Randomized, double-blind, 4-session study in 17 healthy adults (8 female, no cannabis for 60+ days) consuming 0, 10, 25, or 50 mg THC brownies. Blood and oral fluid collected for 8 hours; analyzed by ELISA and LC-MS/MS.

What this study cannot tell us

Small sample (17, 8 female); infrequent users only; single edible form (brownie); 8-hour window may not capture full duration of higher doses; no direct impairment measurements alongside PK; body weight/BMI only partially explains sex differences.

How to read the evidence

Strong: randomized, double-blind, placebo-controlled with both sexes and dual analytical methods.

When this study was published

Published 2020.

The bigger picture

Roadside oral fluid testing for cannabis may detect oral deposition from eating edibles, not actual impairment. The immediate oral fluid detection following edibles (before blood levels rise) means a positive oral fluid test does not confirm systemic THC exposure.

Questions still open

Should drug testing cutoffs differ for men and women? Does oral fluid testing after edible consumption accurately reflect impairment?

Common questions

Do edibles show up differently on drug tests?

Yes. Blood THC peaked 1.5-2 hours after eating a cannabis brownie but was far lower than after smoking. Oral fluid THC appeared immediately (from mouth contact with the brownie, not blood THC), which means oral fluid tests may be positive before the person actually feels any effects.

Do men and women process edibles differently?

Women in this study had higher peak THC and metabolite concentrations than men, partly due to lower body weight and BMI. This suggests women may be more sensitive to edibles at the same THC dose.

Read the original research

Pharmacokinetics of Cannabis Brownies: A Controlled Examination of Δ9-Tetrahydrocannabinol and Metabolites in Blood and Oral Fluid of Healthy Adult Males and Females.

Journal of analytical toxicology, 44(7), 661-671

View on PubMed ↗Publisher’s paper ↗

Citation

Spindle, Tory R; Cone, Edward J; Herrmann, Evan S; Mitchell, John M; Flegel, Ronald; LoDico, Charles; Bigelow, George E; Vandrey, Ryan. (2020). Pharmacokinetics of Cannabis Brownies: A Controlled Examination of Δ9-Tetrahydrocannabinol and Metabolites in Blood and Oral Fluid of Healthy Adult Males and Females.. Journal of analytical toxicology, 44(7), 661-671. https://doi.org/10.1093/jat/bkaa067