The issue of “pot and pets” is a complicated one for veterinarians. More than half of U.S. states have passed legislation permitting medicinal use of marijuana in humans, but these laws apply to people only; they do not apply to animal patients. Veterinarians lack the legal authorization for veterinary use and are not protected in recommending its use. Pet owners who are using medical marijuana for a variety of ailments for themselves or who are aware of cannabis-derived products, are now asking veterinarians about using these products for their pets. Although cannabinoids such as CBD appear to be therapeutically beneficial for conditions such as for the treatment of epilepsy and the management of pain and inflammation associated with osteoarthritis, the available scientific evidence pertaining to their use in animals is limited. Further complicating the issue is that with recreational marijuana becoming law in a number of U.S. states, accidental exposures in pets are on the rise.
When Illinois Governor JB Pritzker signed HB 1438 into law in June, making Illinois the 11th state to legalize recreational marijuana, the American Veterinary Medical Association (AVMA) issued a statement encouraging all pet owners to make sure an increase in legalization doesn’t lead to an increase in pet poisonings.
While marijuana use can be a pleasurable experience for people, the AVMA said, it can be dangerous for dogs. Tetrahydrocannabinol (THC), the psychoactive substance in marijuana that produces a high for humans, is toxic to dogs, and can cause vomiting, incoordination, depression, sleepiness or excitation, low blood pressure, low body temperature and seizures. Death is rare, says the AVMA, but there have been a few cases reported.
In 2019, the ASPCA’s Animal Poison Control Center reported a 765% increase in calls about marijuana ingestion by animals over the same period last year. The Pet Poison Helpline has reported an over 400% increase in marijuana-related calls over the past six years.
“There’s a lot of factors to it,” says Samuel D. Stewart, DVM, DACVECC, at Boston West Veterinary Emergency and Specialty. “We legalized recreational use in Massachusetts, and since the recreational dispensaries opened, we’ve seen an increased number of pets brought in for ingestion of cannabis products. People who never had cannabis products in their house don’t think, ‘Maybe I should put this up and away from where my pet can’t get to it.’”
Edible products — such as pot brownies, candy bars and other baked goods — are especially concerning. Due to its “fat-loving” (lipophilic) nature, THC is highly concentrated in the butter used for such edible products compared to plant material, says the AVMA. Consequently, these products can cause pets to become particularly ill. These products could pose an increased risk due to additional toxic ingredients, such as chocolate, raisins or sugar-free sweeteners such as xylitol, which could compound their toxicity.
A 2012 study published in the Journal of Veterinary Emergency and Critical Care showed that cases of marijuana toxicosis at two Colorado veterinary hospitals quadrupled over a five-year period (2005-2010). During this period, the number of state medical marijuana registrations increased by more than 100 percent. Two dogs died after eating baked goods containing tetrahydrocannabinol (THC), the active ingredient in cannabis, the study reported.
Pets and Marijuana Exposure
Exposure to marijuana is rarely fatal in dogs, according to a study published in Topics in Companion Animal Medicine. The minimum lethal oral dose for THC is more than 3 g/kg, which is more than 1,000 times the dosage where the pet owner can begin to notice behavioral symptoms, such as a glazed look. While the drug has a high margin of safety, medical-grade THC butter is more concentrated, and this is what may have caused the deaths of the two dogs in the Colorado study.
Marijuana is the dried material of the plant Cannabis sativa. Herbal preparations contain over 400 compounds, including 60 cannabinoids, according to a 2012 article published in Therapeutic Advances in Psychopharmacology. The most potent psychoactive cannabinoid is THC (delta 9 tetrahydrocannabinol).
Dogs tend to be indiscriminate eaters, but even if Fido were to wolf down the flowers of a marijuana plant, there wouldn’t be any adverse effect, says Dr. Stewart. “That’s because the flowers have to be heated first to convert to its active form — if a dog were to eat just a bag of flower, nothing’s going to happen,” he says. “They have to eat either an edible or perhaps the oil used for people who are vaping.” Dr. Stewart says most cases at Boston West are due to the pet ingesting edible products.
Fortunately, most marijuana exposures are not serious. “It’s not really a marijuana intoxication — the dog is going to be just fine,” says Dr. Stewart. “I prefer the term ingestion. They’re not poisoned from this. They dog will eat a whole bunch of edibles, for example, and they have symptoms. How much does the pet have to ingest for it to be lethal? That number is astronomically high.”
Getting an Accurate History
Before recreational pot was legalized in Massachusetts, only 25% of clients would be honest about what their pets had ingested when coming to the clinic, says Dr. Stewart. “Even before it was legal, we as doctors don’t care if you have cannabis in the house. We don’t care if you smoke it. Most people think we’re going to report them. That’s rarely ever the case. But there’s that stigma that people don’t want to tell you. Even though now it’s legal, that stigma is still there, but about 50% of people bringing their pets in now [since the state legalized recreational use] are honest [that the ingestion took place in the home].”
The ASPCA’s Animal Poison Control Center (APCC) Medical Director Dr. Tina Wismer says that “the abundance of edibles makes marijuana more enticing to dogs, since they often smell and taste like regular baked goods. Cats, on the other hand, are more attracted by marijuana in its bud form.”
The typical presentation in the clinic is a dog that has a dazed expression, glassy eyes, incoordination, slow response times, and dribbling urine. “They’re really high, but they’re not going to die,” says Dr. Stewart.
Clinical Signs of Marijuana Ingestion
An animal that has been exposed to marijuana generally has signs and symptoms that include depression, ataxia, mydriasis, bradycardia, hypothermia and urinary incontinence, says the APCC. While there are many toxins that can cause ataxia and lethargy, urinary incontinence is not as common and can be a clue as to the exposure. Pets exposed to marijuana may exhibit other signs such as agitation and tachycardia; seizures and coma, although not common, may occur as well.
“The symptoms of cannabis ingestion are incredibly obvious,” says Dr. Stewart. “My technicians diagnose it before I even see the dog. The flip side is that if it’s not cannabis ingestion, then it’s nothing good; it’s something really serious. So I tell clients, ‘If it’s cannabis ingestion, I just need you to tell me, because if it’s not, it’s going to be something way worse.’ That’s the challenging part [of pet owners not being honest].”
Fortunately, most marijuana exposures are not serious.
Veterinary Medicine and Cannabis
Dr. Stewart is interested in “both sides of the coin.” In addition to being a specialist in emergency and critical care at Boston West, he is also involved in Ethos Discovery’s upcoming clinical study on cannabidiol (CBD) for the treatment of pain in dogs with osteoarthritis. Once underway, the study will evaluate the pharmacology profile of CBD in dogs (i.e., how it’s processed in the body), as well as its effectiveness in treating pain in dogs with chronic osteoarthritis.
“There’s a humongous potential for actual therapeutic benefit of CBD products,” says Dr. Stewart. “I support people who want to use these products, but there’s no good avenue for them to do it now. What I tell people is that I believe in the science behind it, but there’s not been the research done [to inform our recommendations]. We don’t know what the dose should be, what the frequency should be, what actual applications for what diseases we can use it for.”
In July 2019, the AVMA submitted comments to the FDA urging the agency to provide regulatory clarity about the labeling, safety, and use of cannabis-derived and cannabis-related products.
Ethical Considerations
The ethical challenge for veterinarians regarding cannabis is the debate over medical use for pets. Pet owners using marijuana for medical purposes may approach veterinarians about the possibility of treating similar conditions — such as pain, seizures, and cancers — in their pets. These clients want to know whether these products are legal, safe, and effective for treating their pets’ medical conditions.
In a recent Facebook poll that we conducted on Today’s Veterinary Practice’s Facebook page, 73% of 180 respondents said clients have asked them about cannabinoid treatments for their pets:
One issue is that these CBD products are not produced by FDA-regulated companies. “There’s no regulation guiding how they make their products,” says Dr. Stewart. “There’s not a wealth of research being done. There’s a few studies; the majority of work that’s been done is at Colorado State, and Cornell. You can probably count on one hand the number of studies that are being done.”
The AVMA encourages well-controlled clinical research and getting FDA approval by manufacturers of cannabis-derived products so that high-quality products of known safety and efficacy can be made available for veterinarians and their patients.
Clinical researchers face obstacles, however. On the federal level, marijuana is classified as a Schedule I narcotic — with the exception of hemp, a type of cannabis that was recently descheduled through passage of the 2018 Farm Bill — and is difficult to obtain legally for purposes of scientific research. Rescheduling marijuana could allow veterinary researchers easier access for medical studies.
“That’s my big hope. I’m happy to see so many companies making products and putting them on the market, but they’re putting them on the market and they’re advertising it as treating a specific condition. I’m hoping the research will advance quickly. CBD is a good launching point. I hope the studies will show that there’s a reason to be looking at whole plant cannabis.”
Learn More
Read a recent survey of what veterinarians know about medical marijuana.
Read about Colorado State’s study about cannabis and dogs with epilepsy.
Visit the Toxicology Archives of Today’s Veterinary Practice.
This article is based on an AVMA press release with additional reporting by Patricia Wuest, Editorial Director of NAVC.