It doesn't matter how hard I try to avoid this question, it always comes up with clients. Perhaps you feel similarly? A group from Ontario, Canada recently published a study evaluating safety profiles of several CBD-oil, CBD/THC-oil and THC-oil containing products in a dose escalation study. The study evaluated 20 dogs in a blinded, placebo controlled (sunflower oil or MCT oil) multidose parallel study.
The following comparisons were made:
1. CBD oil or THC oil compared to MCT placebo
2. CBD/THC combined oil (ratio: 1.5) to sunflower oil
Results
This study contained a lot of data about adverse effects (AE: the new fancy word for side effects) that you might find interesting. The article is linked below. I will focus on the neurological and hepatic side effects.
Overall, they had mostly (n =401/505) mild adverse effects but a few moderate and severe adverse effects were seen. The oils containing THC had the most AE and were also the only groups to show severe AE. Neurologic AE that were noted included tremors and ataxia but AE categorized as "constitutional" included lethargy and hyperesthesia. I did not include the "constitutional" numbers below but could be persuaded that indeed those should have been considered neurological AE as well. Liver values were considered abnormal when they exceeded a 2-fold increase from normal.
1. CBD oil (80 AE): 13 were neurologic; 1 dog had elevated ALP (2.9-fold)
2. THC oil (206 AE): 89 were neurologic*
3. THC/CBD oil (115 AE): 56 were neurologic*; 1 dog had an elevated ALP (3.6-fold)
4. Placebo: 27 AE, 13 were neurologic (!)
* The proportion of GI to neurologic side effects were higher in the groups containing THC compared to placebo or CBD oil only groups.
Moderate side effects were not noted in the CBD oil group and accounted for 22 or 505 AE in the THC and CBD/THC group with also a few dogs in the placebo group.
Severe side effects were noted in 3 dogs - one in the THC only group and 2 dogs in the CBD/THC group. Signs were transient and resolved in 9-28 hours.
A reminder about hepatic metabolism
The elevation of ALP due to CBD results from activation of the p-450 system in the liver. This should sound familiar because it is the workhorse for drug metabolism for drugs such as phenobarbital or zonisamide. Co-administration of CBD and phenobarbital (and probably zonisamide but not in published data for dogs) can affect the metabolism of phenobarbital.
Take away message: What is the big picture here?
My take away from this article was that THC containing products have more neurological side effects compared to CBD containing products and CBD containing products affect liver metabolism. You may be thinking "but I wouldn't recommend THC products for my patients!" and I would support that. And yet, remember production oversight and regulation of these products, especially for animal consumption, isn't robust therefore contamination of THC may be possible. Please note that the State of Wisconsin continues to prohibit prescribing CBD products by vets with clients unless under specific situations. (https://datcp.wi.gov/Documents/VEBCannabis.pdf) therefore this TidBit Tuesday in no way supports or advocates for the use of CBD oil containing products for veterinary patients.
Article link: https://www.frontiersin.org/articles/10.3389/fvets.2020.00051/full#B21
Thanks for reading! Have a great day, and keep those consults coming!