This blog installment looks at the use of cannabis for pets. Topics covered include the history of cannabis use in veterinary medicine, current laws on cannabis for pets, market size and segment, reported experiences from both pet owners and veterinarians, and pet toxicology.
Historical references to the use of cannabis to treat animals tend to focus on horses. In a recent paper in Animals by De Briyne and colleagues (1), they state: “[Ancient] Greek writers reported the use of cannabis for dressing sores and wounds in humans and horses,” and “until relatively recently, cannabis was found in a large number of veterinary medications designed to treat colic, spasmodic colon, and other ailments in equine patients.”
In more recent times, clinical studies of the pharmacology, safety, and efficacy of cannabis for animals tend to be conducted mostly on dogs. The research in this area shows that when compared to studies of other animal species, dogs have a higher density of CB1 receptors in their cerebellum. This makes dogs more sensitive to the effects of tetrahydrocannabinol (THC). Furthermore, dogs metabolize cannabinoids differently than humans, and researchers still don’t know which cannabis metabolites are active for dogs. As a result, most cannabis therapeutics for pets focus on cannabinol (CBD) rather than THC. Finally, the few clinical studies that have been performed on dogs generally examine the use of CBD to treat osteoarthritis or epilepsy, and the studies tend to find CBD to be effective in treating these conditions (1,2).
More generally, CBD may provide benefits for dogs and other animals in the treatment of, for example (3):
When it comes to cannabis and animals, the European Union (EU), Canada, and the United States (US) all distinguish between two primary uses of cannabis for animals, either as a source of nutritional benefits or as a source of therapeutic benefits. Let’s take a closer look at each of those uses.
On the one hand, hemp seed products provide nutritional benefits when used in animal food and livestock feed.
The EU, Canada, and the US all recognize this potential. At the same time, however, an overriding concern is the potential for people to become “unintentionally exposed” to cannabinoids used for animals “through meat, milk and eggs”(4). Consequently, both Canada (1) and the US (4) prohibit using hemp products in livestock feed. In contrast, the EU does allow the use of hemp seed products in animal feed as a source of “crude protein and essential fats” (1).
On the other hand, cannabinoids (such as CBD and THC) have the potential to provide therapeutic benefits when used in health and wellness products.
In the EU, despite a lack of government approval of any cannabis animal products for therapeutic uses, many companies are currently selling such products with wellness claims (1):
There are many companies in the EU marketplace today selling ‘nutritional supplement’ cannabis-derived products for dogs, cats, and horses, some of which make what clearly appear to be therapeutic feed claims. These products are being promoted as aids for itching, anxiety, nausea, poor appetite, seizures, cancer, digestive problems, inflammation, immune disease, and reduced mobility due to joint pain in animals. It is against the law to make therapeutic feed claims about nutritional products.
None of these products are approved for therapeutic use; so, legally, veterinarians cannot “offer scientific advice on the effectiveness of a nutritional product to treat a disease” (1). Presumably, the government is simply not enforcing the laws regarding wellness claims in marketing. It’s not clear whether or not the government is enforcing laws against veterinarian advocacy for these products either.
Canada allows cannabis-derived veterinary health products (VHPs) only when derived from the seeds of the plant and when containing minimal amounts (< 10 ppm (mg/kg)) of THC (1). Notably, by precluding use of hemp flower products, the Canadian government is also limiting the amount of CBD that can be cost effectively included in cannabis VHPs.
Regardless of the recognized potential for cannabis’s therapeutic benefits, the fear that human food products may be contaminated through animal consumption of cannabis has led to a ban on their use in the US (1): “Accordingly, as of this writing , there are no hemp- or marijuana-derived foods, drugs, or supplements approved for use in animals in the US.” Furthermore, the position of the American Veterinary Medical Association (2) is that there is not enough scientific evidence to support any therapeutic benefits of CBD for dogs (3). Nevertheless, some US states have passed laws loosening the federal restrictions on cannabis pet products (1).
Veterinarian laws in the US ban veterinarians from prescribing cannabis products for animals. At the same time, however, “veterinarians may be permitted to discuss cannabis with pet owners or recommend cannabis to companion animals, depending on state law.” Yet, laws vary dramatically by state, “and there could be real consequences for veterinarians who run afoul of these laws, including a loss of their DEA [Drug Enforcement Administration] registration. Before discussing cannabis with clients, veterinarians should ensure they are aware of all relevant information in the state where they practice.” As a point of clarification, cannabis-derived products for pets are illegal, which means veterinarians cannot sell these products. Yet, recommending cannabis products for pets is not against the law (4) (see Figure 1).
Despite tight international laws on the use of cannabis products for animals, the market for CBD products for pets is relatively large and quickly growing. Grand View Research reported (5) that in 2022 global CBD pet products generated $196 million in sales, and the market “is expected to grow at a lucrative compound annual growth rate (CAGR) of 31.8% from 2023 to 2030.” The report further indicates that the largest market segments were as follows (5):
Surveys of pet owners and veterinarians indicate that CBD use in pets has largely been driven by pet owners and CBD companies (6–8). Notably, most pet owners who use CBD for their pets also use CBD themselves (8), and their motivations for using CBD products rather than more traditional veterinary products is that they believe CBD is more natural and more effective (9). Most users are using CBD products to treat veterinarian-diagnosed problems, but they did not generally start using CBD products on the recommendations of their veterinarians, and they’re not necessarily discussing their use of CBD products on their pets with their veterinarians (6–8). The most common conditions being treated with CBD include seizures, cancer, anxiety, and arthritis(7).
In short, these surveys are showing that therapeutic cannabis use by pets is similar to therapeutic cannabis use by people in that:
Finally, most pet owners purchase their pet products online, or alternatively in pet stores, and most pet owners feel they lack sufficient information on appropriate CBD usage and dosing for their pets (6).
In 2019, Lori Kogan and Regina Schoenfeld-Tacher published an insightful survey of US veterinarians on their experiences with cannabis for pets (10). In states that have legalized recreational cannabis use, more than 60% of veterinarians receive daily or weekly inquiries from pet owners about CBD for pets. In non-legal states, that frequency drops to less than 25%. The most common condition for which pet owners seek advice is pain, but inquiries about CBD for anxiety and seizures are also common.
Of course, over time veterinarians have become more comfortable—relatively speaking—in discussing cannabis use for pets. Yet, while a larger majority of veterinarians (roughly 70%) feel comfortable discussing CBD for pets with other veterinarians, a smaller minority (roughly 55%) feel comfortable discussing it with patients. In fact, only about one in four of veterinarians will “advise” clients about CBD use for their pets, less than one in five veterinarians will recommend CBD, and less than one in 10 will prescribe CBD. The reasons given for not advising, recommending, or prescribing cannabis was (in decreasing frequency): lack of knowledge by veterinarians, lack of CBD efficacy, lack of legality, and potential toxicity.
While most veterinarians have little clinical experience with CBD products for pets, most perceive it as being very or somewhat helpful for a variety of conditions, including pain, anxiety, seizures, storm or firework phobia, motion sickness, and vomiting. Yet, a majority of veterinarians feel their state veterinary organizations have not provided them with sufficient guidance on the use of CBD or cannabis for pets for them to feel comfortable practicing within state or federal laws.
In 2022 cannabis products were listed on the American Society for the Prevention of Cruelty to Animals’ (ASPCA’s) top 10 list of pet toxins for the first time, coming in at number 10 (11). Importantly, it was noted by Brutlag and Hommerding (12) that “ingestion or inhalation of THC carries a high morbidity but low mortality rate.” As we might expect, two-thirds (66%) of calls to the Pet Poison Helpline involve pets eating edibles (12).
Nancy De Briyne and colleagues provide a wealth of information regarding marijuana toxicosis in pets (1): In addition to THC, other ingredients in cannabis products, including chocolate, raisins, or xylitol, may cause problems for pets. At the same time, CBD products may also be toxic, especially if they contain products other than CBD. The onset of signs of cannabis toxicosis in dogs typically occurs within 30–90 minutes of exposure and can last up to 96 hours. The most common signs of excess cannabis exposure in dogs and cats include:
The authors state (1): “Because no antidote has been described to date, the treatment of cannabis toxicosis consists of supportive care. Because of the wide margin of safety of most known cannabinoids, toxicosis is rarely fatal.” And finally, “Recovery may take 24 to 72 h, or longer (up to 5 days), depending on the ingested dose.”
Documented early historical use, together with more recently established mechanisms of action, support clear applications for using cannabis to treat pets. And given the prevalence of pets in society (more than half of Americans own cats or dogs) and the devotion of owners towards their pets (in 2022 owners spent roughly $125 billion on their pets) (13), it’s no surprise that owners are preempting both the laws and their doctors’ ability to guide them in treating pets with CBD. It’s also no surprise that early users of CBD for pets are owners who have used CBD for themselves.
The biggest threat cannabis poses for pets appears to be the same as that for children: unwitting consumption of THC products, which may cause cannabis toxicosis. The good news, though, is that most accidental overdoses are temporary in nature, with no long-lasting effects. Similarly, the biggest challenge cannabis poses for pet patients appears to be the same as that for human patients: having the laws and doctor education catch up to human and pet use.
Ruth Fisher, PhD, is a systems design researcher and analyst. She analyzes markets to determine how environments shape outcomes. She is co-founder of CannDynamics, and author of The Medical Cannabis Primer and Winning the Hardware-Software Game: Using Game Theory to Optimize the Pace of New Technology Adoption. Dr. Fisher has worked in the technology and healthcare sectors on behalf of technology companies, early-stage researchers, physicians, and technology start-ups.