Which Dogs Should Not Receive CBD?

Cannabidiol (CBD) is one of over 90 cannabinoids produced by the Cannabis sativa plant and has great potential for therapeutic application in veterinary medicine. The 2018 Farm Bill legalized the regulated production and use of hemp and hemp products that contain less than 0.3% tetrahydrocannabinol (THC) in the United States, and since then, CBD products have become widely available and interest in using CBD to treat our pets is increasing. This is due to not only anecdotal reports, but also scientific evidence of beneficial behavioral and health effects, especially for such conditions as pain (particularly with arthritis), inflammation, anxiety, seizures, and immune system modulation in companion animals.

Overall, CBD use in dogs appears to have a good safety profile and is at low risk for side effects. “Appears” is the key word here, however. Because cannabidiol and other hemp products were federally illegal until 2018, we are only now beginning to see the results of recent scientific studies conducted on these products.

It is known that dogs, like humans, have an endocannabinoid system (a complex cell signaling system); however, experts haven’t yet determined how it all works. Because we are in only the very early stages of understanding just how cannabinoid-based medications affect the canine body, we need to be cautious in administering CBD to our dogs. While we wait for the results of new and ongoing research, here are some key points to be aware of when considering CBD:

  • Currently, there are no veterinary drugs containing CBD that are approved by the United States Food & Drug Administration (FDA). CBD products are currently sold as nutritional supplements and “drug claims” about their use are strictly illegal.
  • There is little documented research, control, or regulation over CBD products. This can result in highly varying compositions, concentrations, and quality, even from one batch to the other of the same product. Because of this, consumers may not know what any individual product contains.
  • A recent study (“Cannabinoid, Terpene, and Heavy Metal Analysis of 29 Over-the-Counter Commercial Veterinary Hemp Supplements”, Vet Med (Auckl). 2020;11:45-55) by Cornell College of Veterinary Medicine and ElleVet Sciences, a manufacturer of pet CBD products, tested 29 CBD pet products. Label guarantees to the cannabinoid concentration contained in the supplement were present on 27 of the 29 products, however, only 10 of the 27 “were within 10% of the total cannabinoid concentrations of their label claim.” Several tested below their label claims of cannabinoid concentration, and two products were found not to contain any CBD at all. Heavy metal contamination was found in four of the products, with lead being the most prevalent contaminant (three products).
  • Owners and veterinarians considering the use of CBD need to be aware of the prevalence of low concentration products. Obtaining a certificate of analysis (COA) from a third party laboratory will enable correct calculation of dosage.
  • There is not yet any data available as to the effects of long-term administration of CBD to dogs. It is also not known if there is any cumulative effect.
  • Of particular concern is any potential interaction between CBD and other medications. Because CBD is metabolized by the cytochrome P450 family of enzymes, it can affect the metabolizing of the other medications in the system. In turn, this can alter the efficacy of these other drugs, either by enhancing their activity or inhibiting the desired activity. Studies with humans have demonstrated that this interaction has impacted drug concentrations in the blood. It has been determined that there is the potential for interaction in humans with the drugs warfarin, tacrolimus, theophylline, ketoconazole, and zonisamide. As these drugs are also used in dogs, it is possible that that there may be interactions in the canine body as well. Other medications that CBD may interfere with include antibiotics, antipsychotics, antidepressants, blood thinners, and any other drugs metabolized by P450 enzymes.
  • Scientific studies have shown that CBD can cause an increase in the liver enzyme alkaline phosphatase (ALP), but the significance of this is not yet known. CBD is thought to be able to enhance the effects of certain drugs. This may present an opportunity or need to reduce the dose of certain medications that are administered to a patient who is also being given CBD.
  • As NSAIDs, Tramadol, Gabapentin, and anti-anxiety drugs rely on P450 enzymes for metabolizing, approach the addition of CBD carefully.
  • When given with trazadone, CBD was found to inhibit the ability of trazodone to lower blood cortisol in a recent study by Morris et al (The Impact of Feeding Cannabidiol [CBD] Containing Treats on Canine Response to a Noise-Induced Fear Response Test, Front. Vet. Sci., 22 September 2020). This highlights the potential drug interactions associated with CBD and may support previous work that shows CBD to be a potent inhibitor of the cytochrome P450 family of enzymes.

Continued research is essential to furthering our understanding of how CBD affects the canine body. As with any medication, consult your veterinarian before treating your dog with CBD.

Featured photo: aydinmutlu/Getty Images

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