April 20th has arrived, officially 420 Day in the marijuana advocacy community. Before lighting up at 4:20pm or indulging in a special brownie, read The Meowing Vet‘s article on the effects of marijuana and cannabis in pets. We’ll address various viewpoints on cannabis, including how marijuana is toxic to dogs and cats as well as potential benefits of certain cannabinoids in veterinary medicine.
Learn more below…
Note: The following article is predominately based upon current animal and veterinary laws regarding cannabis use in the United States of America as of the time of publication (April 2018).
Introduction
The conversation of marijuana in the veterinary community has expanded in recent years. Marijuana usage in the United States is still a hot issue, pulsing in news headlines as discussions continue regarding potential health benefits of cannabis, the decriminalization of pot in some locations, and an increase in the number of medical marijuana dispensaries for humans. In human medicine, cannabis and its derivatives have been used to alleviate a plethora of ailments ranging from cancer-related inappetance and chronic pain, arthritis, anxiety, depression, and certain neurological disorders. Since our dogs and cats are members of our families, pet owners naturally wonder if cannabis can also help our furry friends.
For the most part, marijuana and cannabis are regarded as synonyms for the Cannabis sativa plant. The key chemical components of marijuana are contained in the leaves, flowering tops, seeds, and resin of the plant. These chemicals are termed cannabinoids, the main of which are tetrahydrocannabinols (THC) and cannabidiols (CBD), which develop when the plant is dried and processed. An exemption of cannabinoid properties lies in hemp, the fibrous components of the Cannabis plant; hemp (and hemp seed oil) is largely derived from the stalk of the plant and harbors no or only trace levels of THC or CBD. Therefore, hemp has minute to no recreational drug potential and is predominately utilized as a natural fiber source for paper goods and textiles (not to be confused with hemp oil, which contains a high level of cannabidiols – note: hemp oil and hemp seed oil are different).
Both THC and CBD affect the nervous system. THC is the psychoactive chemical used recreationally by humans to achieve a euphoric state achieved by altering levels of important neurotransmitters in the brain (serotonin, dopamine, and norepinephrine). THC also affects the nervous system of dogs and cats, but it does not cause the same feelings reported as pleasant by human users. In fact, THC can achieve the opposite in companion animals, causing anxiety in these pets while also being very toxic otherwise, depending on dosage (read below for details).
CBD is regarded as reducing anxiety, depression, and pain in human users while also being beneficial for various psychoses and neurological disorders such as seizure activity and epilepsy as well as Parkinson’s disease. CBD is also thought to have anti-inflammatory, anti-itch, antioxidant, antibacterial, and antifungal effects. CBD functions at cell receptors on neurons and in the gastrointestinal system (CB1 receptors) by causing the release of the neurotransmitter GABA. CBD also triggers a response of certain cell receptors of the immune system (CB2 receptors). The cerebellar region of the brain in dogs has been found to have a large number of CB1 neuron receptors, so the future use of appropriately tested and dosed CBD products has the potential to positively impact canine health. Research centered around the use of cannabis products in felines is currently lacking.
Edited on May 17, 2018 to add: Cornell University College of Veterinary Medicine recently completed a clinical study investigating the role of CBD in alleviating canine osteoarthritic pain, showing improvement in the pain management of treated dogs.
Looking for a calming treat for your dog? Learn what ingredients you should look for in this article for The Anxious Pet.
Marijuana Toxicity in Dogs and Cats
As discussed, THC is the component of marijuana that is toxic to dogs and cats at certain doses when either inhaled or consumed. Depending on the food ingredients in any edibles ingested by a pet, concurrent toxicities may also occur, such as chocolate, raisin, or xylitol toxicity. In addition to marijuana plant exposure (via joints, bongs, and pot-based edibles), synthetic cannabinoids (dronabinol, nabilone, and synthetic THC) prescribed to human patients should be kept away from dogs and cats as exposure can be fatal to pets due to high concentrations of THC. Fortunately, however, most marijuana toxicity cases in pets are not deadly, though dogs and cats can become very ill. Marijuana affects the central nervous system of pets within 30 minutes to 2 hours following exposure. The effects can last up to 3 days in some cases. If you know or suspect that your dog or cat has come into contact with pot, you are highly encouraged to disclose this information to your veterinarian for the appropriate diagnosis and treatment of the pet whose well-being you’re responsible. The American Veterinary Medical Association (AVMA) clearly states that “veterinarians have no ethical or legal obligation to report marijuana toxicosis to any authorities; their focus is on patient care, which requires an accurate history.” Therefore, please inform your vet of any potential for marijuana exposure to your pets without fear of legal action.
Signs of Marijuana Toxicity in Dogs & Cats
Depression and lethargy (can progress to a stupor or even a coma and death)- Hyperesthesia (an unpleasant and frightening state of increased sensitivity to physical stimuli) or other abnormal behavioral status, such as “fly-biting”
- Wobbliness (ataxia) or a stiffened stance with a dull mental state or drowsiness
- Muscle tremors or seizures
- Decreased appetite
- Vomiting
- Salivation/drooling
- Dribbling urine due to lack of bladder control
- Dilated pupils (mydriasis) with a “glazed/stoned look”; red eyes (conjunctival injection); eyes twitching back and forth horizontally (nystagmus)
- Low body temperature (hypothermia)
- Heart rate may be increased (tachycardia) or decreased (bradycardia); blood pressure may be low (hypotension)
Diagnosis and Treatment of Marijuana Toxicity in Dogs & Cats
Diagnosis of marijuana toxicosis in pets is based upon reported exposure, the clinical signs depicted above, as well as subsequent urine or blood tests used to detect THC levels (both tests have their diagnostic flaws but may be useful in some cases).
The treatment of marijuana toxicosis involves supportive care only (i.e. managing symptoms) since no antidote currently exists. If the aforementioned clinical signs have not yet developed following the immediate ingestion of marijuana, your vet may induce vomiting in your pet to prevent THC absorption in the GI tract. In these early cases, activated charcoal may also be administered orally to help bind the toxin. Regulating vital signs (body temperature, heart rate, respiratory rate) will also be a key feature of therapy. Anti-nausea medications may also be given to treat vomiting, and fluids may be administered to correct dehydration and electrolyte disturbances. Anti-convulsant drugs or tranquilizers may also be necessary to use in some cases. 
Furthermore, harsh stimuli such as bright lights, loud noises, and sudden movements are also avoided to protect these patients’ fearful, anxious mental states.. Pets often remain in hospital at least 24 hours before being discharged from the veterinary clinic. Long term effects are unlikely.
As previously stated, canine and feline death from marijuana toxicity is uncommon but does occasionally occur. Pet owners are strongly urged to responsibly store and use any marijuana products well away from their pets, and cannabis should never be purposefully offered to any animal.
Can Cannabis Improve Your Pet’s Health?
As veterinary students, the topic of marijuana in vet school was confined solely to our Toxicology course in which we discussed the toxic effects of accidental marijuana inhalation or ingestion by dogs or cats. Once out in practice as a veterinarian, I was suddenly inundated with questions from well-meaning clients who wanted to know if certain properties in the Cannabis sativa plant could benefit their pets and whether or not they could trust supplements marketed for companion animals. However, many veterinarians are not well versed with therapeutic 
cannabinoid supplementation in dogs and cats, mainly because sources were not widely and legally available until recently and because not much research on potential health benefits in pets has been performed. More medical and veterinary clinical trials centered around the infamous five-leaved plant are currently in the works, including a study at the Colorado State University Veterinary Teaching Hospital investigating the role of cannabidiol (CBD) in treating dogs with epilepsy. Additionally, a 3-year study on the effects of CBD on canine bladder cancer has commenced at the University of Guelph’s Ontario Veterinary College.
With more elaborate information in our educational armory and because more inquisitive pet owners are asking for our input, we veterinarians are becoming better able to advise our clients concerning the negatives and possible positives of cannabis derivatives for dogs and cats. With the legalization of marijuana in several U.S. states and jurisdictions and with other states proposing bills to do the same, marijuana may be more readily available to many individuals. Therefore, either accidental or purposeful exposure by pets to high levels of marijuana is expected to lead to an increase in toxicity cases.
The U.S. Food and Drug Administration (FDA) currently has no protocol to measure the safety or efficacy of marijuana or similar dietary supplements intended for animal use. Therefore, pet owners should take heed when using such products, as many are often illegal to administer to pets and may be non-therapeutic or even harmful to dogs and cats. This includes the use of hemp feed for livestock as well as administration of cannabis to companion animals via direct marijuana exposure or use of CBD oil, CBD chews, and THC or CBD-based nutritional supplements — all of which are currently unauthorized by the FDA and largely regarded as illegal in the United States, both for purchasing and/or for administering to pets. While industrial hemp itself is not illegal to purchase, no FDA guidelines currently exist for animal use. Please keep in mind that some CBD products (such as hemp oil) are marketed as being derived from legal hemp, but this is often untrue. Obtaining such CBD-based products, though they may be legal for purchase, are illegal to administer to animals. Additionally, certain products claiming to contain only CBD may also include toxic THC due to lack of FDA testing regarding these products’ manufacturing.
At the present time in the U.S., no veterinarian may prescribe or recommend cannabis-based products for their animal patients, even in states where human use of medical marijuana is legal. More veterinary research and safeguarding by the FDA is clearly necessary at this point in time to support the potential health benefits that appropriate doses of cannabis may yield for pets. The possibility of utilizing cannabidiols in veterinary medicine has promise. However, more time and work is certainly required first to understand whether or not controlled cannabis use in dogs and cats may reduce anxiety, alleviate chronic pain, stimulate appetite, and aid in the control of epilepsy. In the meantime, pet owners should be very cautious with the use of CBD products and should prevent the accidental inhalation or ingestion of pot by dogs and cats.
Despite your well-meaning intentions based in plans to help your pet, being overzealous by using CBD products in these very early stages of research and pre-regulatory marketing may cause more harm than good. The best thing you can do for your dog or cat right now is to wait… keep yourself out of potential legal trouble, adhere to your personal veterinarian’s other treatment plan recommendations for your pet, and stay informed with reliable sources such as via your vet concerning cannabis research for pets.– Maranda Elswick, DVM
Always consult with your veterinarian before offering any cannabis product to your dog or cat as many are illegal or may be unsafe, be honest with your vet if your pet has been exposed to marijuana, and keep your pot stash and edibles out of your pet’s reach.
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