Written by: Dr. Chip Coombs
With the legalization of cannabis in Canada just around the corner, there has been a lot of buzz about its potential medical benefits. Medical cannabis has been touted as a panacea for just about every medical condition in humans that you could imagine. Like many new medical treatments, however, there is a lot more initial hype and anecdotal support than there is solid scientific support.
One should initially appreciate that not all cannabis is created equally. There are a large variety of cultivation techniques and the methods of preparation are also varied. The cannabis plant – Cannabis sativa – is used for both marijuana and hemp. The main difference is that hemp is cultivated for its fiber content with extremely little psychoactive components, whereas medical and recreational cannabis (marijuana) is cultivated for the high concentrations of chemicals known as cannabinoids. Marijuana also contains one particular cannabinoid known as THC (tetrahydrocannabinol) which is responsible for the psychoactive effects in humans and is presumed to be the cause for the toxic effects to our pets. However, to date, no work has been done to establish whether or not even medical cannabis is completely safe for pets.
In veterinary medicine, with the imminent increased availability of cannabis, there are two issues of interest. Firstly, what are the possible benefits to our pets from medical cannabis and secondly, how do we prevent our pets from being exposed to the toxic effects of accidental consumption of recreational cannabis?
Based on research done in lab animals and to a lesser extent in humans, there may well be potential medical benefits from judicious use in companion animals, but as is often the case with this inter-species extrapolation, there are risks as well. There are different types of cannabinoid receptors and the ones of interest in medicine are categorized as CB1 and CB2. No two species will process drugs/ chemicals in identical ways and so to assume that a dog or cat will receive the same benefits as a human with no side effects would be a risky proposal. There are also significant differences between dogs and cats, which will complicate the situation. Dogs have many more cannabinoid receptors than humans or cats and so accurate dosage will be a concern.
Areas in human medicine where there is some supporting evidence is the use of cannabinoids for the treatment of chemotherapy induced nausea and vomiting. The other area of support comes from their use in the treatment of chronic pain, such as arthritis. There is, however, no evidence that cannabinoids are of any value for the treatment of acute pain such as that experienced post-operatively. Cannabis has also shown promise in the treatment of some types of pediatric epilepsy.
There are presently cannabis-based products on the market for our pets in B.C. and some US states, as well as online. However, in spite of the claims, there is no consistent scientific indication that they have any benefits. To complicate matters, at the moment the regulations governing the labeling of these products or the quality of the cannabinoids upon which they are based are not stringently enforced. As a plant cannabis is grown under intense production techniques, one can anticipate that herbicides will be used and the levels of these chemicals in the finished product is unknown to the consumer. Additionally, how the product is dried and prepared is also highly variable and the impact on the final product is very significant. Hence, until these variables are better regulated, one can never be sure just what is in the final product. Even in states that have labeling and quality control regulations for medical cannabis, there can be significant variations in the finished product. A study done by the FDA in the US found that almost 90% of the products that they tested did not meet their label claims. At the moment, no such regulations exist for veterinary destined products and so the potential variabilities and risks are that much higher.
To date, there is limited concrete evidence to support the use of medical cannabis for any condition in our pets. This paucity of supporting research is largely due to the strict laws that previously existed which regulated the availability and usage of cannabis. With these laws now changing, one can expect that more research will begin in earnest and hopefully evidence-based supportive research will be forthcoming.
However, surveys done amongst pet owners in the U.S. anecdotally report that most owners felt an improvement in the pet’s condition (these conditions included chronic pain, inflammation, anxiety, seizures, and age-related behavioural changes) upon using these cannabinoid-based products. As intriguing as this appears with respect to the efficacy of these products, it is also worthwhile knowing that the “caregiver effect”, i.e. the pet owner’s perception, can have a very significant bias on the actual positive impact from administering a product to their pet. In other words, giving a placebo to their pet resulted in 55% of dog owners and 80% of cat owners feeling their pet had improved.
The concern about our pets being more exposed to the toxic effects of cannabis once legalized is borne out by what has happened in the those US states that have legalized cannabis. Pet Poison Helpline has reported an increase of about 450% of calls relating to the accidental ingestion of marijuana – mostly in dogs. Veterinarians are used to dealing with these cases, so it would be safe to assume that the actual number of intoxication cases is much higher. Typical clinical signs include disorientation, ataxia, and urinary incontinence. Fortunately, to date, there have been very few cases of lethal cannabis ingestion. However, as newer and more concentrated forms are developed, this may not be the case in the future. As with any product that is toxic to our pets, such as dark chocolate and xylitol, it behooves owners who have either medical or recreational cannabis in their home to ensure that it doesn’t get consumed by inquisitive pets. If you feel the need to try a cannabinoid-based product, as part of the treatment for your pet’s condition, please discuss the pros and cons with your veterinarian first.