MedicalResearch.com Interview with:
Alex Straiker PhD
Psychological & Brain Sciences
MedicalResearch.com: What is the background for this study?
Response: We’ve known for almost 50 years that cannabis can lower ocular pressure but the mechanism of action was still unknown. Most of the work on this stopped well before the cannabinoid receptors were discovered in the early 1990s.
Over the last several years we have determined that three different cannabinoid receptors (CB1, GPR18, and GPR119) each can lower pressure in mice when activated. Once this was established, it made sense to go back to THC (and CBD) to see how they act.
MedicalResearch.com: What are the main findings?
Response: There are four main findings.
- Probably the most interesting is that CBD raises ocular pressure in mice. Ours isn’t the first study to show this but we do show how it works.
- Our second major finding is that THC lowers pressure through a combination of CB1 and GPR18 receptors.
- The third major finding is that the effect of THC is sex-dependent, with longer effects in male mice.
- Lastly, CBD cancels out the pressure-lowering effects of THC, probably by blocking CB1 receptors.
MedicalResearch.com: What should readers take away from your report?
Response: There are two main take-homes.
- There is a real possibility that CBD elevates ocular pressure and therefore the risk of glaucoma as a side-effect. This is significant given the widespread (and growing) availability of CBD and its recent FDA approval as a treatment for Dravet’s Syndrome. Second, the sex-dependence is significant in and of itself but also because the current AAO position that topical THC is ineffective as a glaucoma therapy is based on four studies, three of which were small mixed-sex subject pools. If the sex-dependence holds for humans, then it is possible that those studies yielded a false-negative result.
MedicalResearch.com: What recommendations do you have for future research as a result of this work?
Response: The question of whether CBD raises ocular pressure in humans should be revisited and should be monitored in patients being treated for Dravet’s Syndrome.
Sally Miller, Laura Daily, Emma Leishman, Heather Bradshaw, Alex Straiker. Δ9-Tetrahydrocannabinol and Cannabidiol Differentially Regulate Intraocular Pressure. Investigative Opthalmology & Visual Science, 2018; 59 (15): 5904 DOI: 10.1167/iovs.18-24838
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