High-dose CBD reduces THC absorption when both are inhaled together
When CBD and THC were co-administered by vaporization, high-dose CBD significantly decreased the systemic availability of THC, with frequent cannabis users showing higher availability of both compounds.
Quick Facts
What This Study Found
In a randomized, double-blind, crossover study, concomitant inhalation of high-dose CBD significantly decreased the systemic availability of THC. Population pharmacokinetic models showed that frequent cannabis users had higher systemic availability of both THC and CBD compared to infrequent users.
Key Numbers
High-dose CBD significantly decreased THC systemic availability. Frequent users had higher availability of both compounds. Population PK models developed for both THC and CBD.
How They Did This
Randomized, double-blind, crossover, placebo-controlled design. THC and/or CBD in ethanol were vaporized and inhaled. Plasma concentrations analyzed and population pharmacokinetic models developed by pooling with published data.
Why This Research Matters
Many medical cannabis users consume both THC and CBD. Understanding how they interact pharmacokinetically is essential for dosing guidance. The finding that CBD reduces THC availability could explain why CBD-rich products feel less intoxicating.
The Bigger Picture
This finding has practical implications: adding CBD to THC products may actually reduce THC exposure, not just modulate its effects subjectively. This could inform product design and dosing recommendations for medical cannabis.
What This Study Doesn't Tell Us
Relatively small sample; vaporized administration only (results may differ for oral or sublingual routes); pooled data from different studies for PK modeling; acute dosing only.
Questions This Raises
- ?Does the CBD-THC interaction hold for oral administration?
- ?Should medical cannabis dosing account for CBD-mediated reduction in THC availability?
Trust & Context
- Key Stat:
- High-dose CBD significantly decreased THC systemic availability when co-inhaled
- Evidence Grade:
- Moderate: randomized, double-blind crossover design with PK modeling, though sample size was limited.
- Study Age:
- Published 2020.
- Original Title:
- Model-based analysis on systemic availability of co-administered cannabinoids after controlled vaporised administration.
- Published In:
- Internal medicine journal, 50(7), 846-853 (2020)
- Authors:
- Liu, Zheng(2), Galettis, Peter(4), Broyd, Samantha J(2), van Hell, Hendrika, Greenwood, Lisa-Marie, de Krey, Peter, Steigler, Amy, Zhu, Xiao, Schneider, Jennifer, Solowij, Nadia, Martin, Jennifer H
- Database ID:
- RTHC-02690
Evidence Hierarchy
Participants are randomly assigned to treatment or placebo groups to test cause and effect.
What do these levels mean? →Frequently Asked Questions
Does CBD reduce the effects of THC?
This study found that co-inhaling high-dose CBD reduced the amount of THC that reaches the bloodstream. This pharmacokinetic interaction could contribute to why CBD-rich products feel less intoxicating.
Do frequent cannabis users absorb more THC?
Yes. Frequent users had higher systemic availability of both THC and CBD compared to infrequent users, possibly due to differences in inhalation technique or metabolic adaptation.
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Cite This Study
https://rethinkthc.com/research/RTHC-02690APA
Liu, Zheng; Galettis, Peter; Broyd, Samantha J; van Hell, Hendrika; Greenwood, Lisa-Marie; de Krey, Peter; Steigler, Amy; Zhu, Xiao; Schneider, Jennifer; Solowij, Nadia; Martin, Jennifer H. (2020). Model-based analysis on systemic availability of co-administered cannabinoids after controlled vaporised administration.. Internal medicine journal, 50(7), 846-853. https://doi.org/10.1111/imj.14415
MLA
Liu, Zheng, et al. "Model-based analysis on systemic availability of co-administered cannabinoids after controlled vaporised administration.." Internal medicine journal, 2020. https://doi.org/10.1111/imj.14415
RethinkTHC
RethinkTHC Research Database. "Model-based analysis on systemic availability of co-administ..." RTHC-02690. Retrieved from https://rethinkthc.com/research/liu-2020-modelbased-analysis-on-systemic
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.