By Al Chicoine, Veterinary Clinical Pharmacologist, Western College of Veterinary Medicine

Many pet owners are considering using cannabidiol (CBD) for themselves or their animals, for a variety of medical conditions. CBD is a cannabinoid substance (derived from Cannabis plants) that has demonstrated potential for analgesic and anti-inflammatory effects. However, CBD is not considered to have significant psychoactive effects (i.e., unlike other cannabinoids such as THC, people and animals don’t “get high” after CBD ingestion). Increasing anecdotal claims are made for oral CBD use in animals – but is it actually safe and effective? As usual, the answer is “It depends!” Our team at the Western College of Veterinary Medicine has been studying CBD in dogs and cats since 2019, with colleagues worldwide performing similar studies.

Evidence of efficacy:

• The disease condition in dogs with the most published evidence for CBD efficacy is currently osteoarthritis, with at least four small clinical studies performed. Early studies generated positive, though not necessarily overwhelming, results when comparing treated dogs to a negative control group (placebo). However, not all subsequent studies have shown the same benefit versus a placebo group. It appears as though CBD may have some positive role to play in the treatment of osteoarthritis – but at this time, it should definitely NOT be considered a replacement for other well-established osteoarthritis treatment methods (such as NSAID and other anti-inflammatory drugs, or newer monoclonal antibody therapies).
• One of the first promising medical uses of CBD in people was for treating pediatric epilepsy patients. Similar research in epileptic dogs and cats has also shown positive results, but again, with only limited data. As with osteoarthritis, if CBD is to be used in epileptic dogs it will likely be as an “add-on” therapy (rather than simply replacing current medications).
• Our research team is currently conducting a clinical trial using oral CBD after a specific orthopedic surgery in dogs (in addition to standard pain medications), and other researchers are evaluating CBD use after other types of major surgery. Insufficient data have been published to make any recommendations at this time.

Evidence of Safety:

• Most studies have demonstrated that oral CBD is generally safe in dogs and cats. Our own research has indicated that at low to moderate doses (2 – 5 mg CBD/kg body weight), for durations up to two weeks, dogs and cats tolerate oral CBD quite well. Instances of vomit or diarrhea were very rare, and animal behaviour was generally not affected (particularly in cats). Some dogs were thought to be a little “quieter” after receiving CBD, but veterinarians who were blinded to the treatment groups could not reliably distinguish between CBD- or placebo-treated dogs.
• The most commonly observed adverse effect is a mild increase in liver enzymes. Pet owners administering CBD chronically to their animal should ask their veterinarian if monitoring liver enzymes through routine bloodwork is appropriate, especially for animals currently receiving other medications that are metabolized by the liver.

CBD product quality and consistency:

• However, we must be extremely cautious when comparing studies evaluating CBD efficacy or safety. Unless the studies are performed with the same CBD products and dosing regimens, the results should not be considered directly comparable.
• Unlike many pharmaceutical products, each CBD formulation is unique and therefore not interchangeable with other CBD products. Two CBD formulations can have very different concentrations – not just of CBD, but also other cannabinoids (including potentially THC). Other product characteristics, including the type of oil base used or presence of other plant-based compounds, can substantially influence the amount of CBD absorbed from the animal’s digestive tract. For example, some published studies using certain CBD formulations administered doses many times higher than those used in our (and other researchers’) studies – and yet detected substantially lower concentrations of CBD in the animals’ blood! An appropriate dose for one CBD product may end up being completely ineffective – or worse, toxic – if applied to other CBD formulations. Administration of CBD with food also tends to increase the amount absorbed into the blood, therefore switching between “fed” or “fasting” dosing is not recommended.
• As well, our research evaluating “grey-market” CBD products sold in some pet stores showed a dramatic variance in product quality (i.e., some products contained dramatically different CBD concentrations than stated on the label). Product labels were often incomplete, with dose recommendations almost certain to be ineffective.

Pet owners choosing to administer CBD to their animal should therefore ensure that a consistent product and dose regimen are used. Finally, pet owners should note that while sale of cannabis has been legal in Canada since 2018, veterinarians are not currently authorized to prescribe cannabis products (including CBD) to animals. However, anyone interested in CBD use for their animals are still encouraged to discuss potential usage with their veterinarian.