Medical Cannabis: Is It Good For Our Dogs?

A Bulldog who spent two years either lying down or throwing up plays like a puppy thanks to a daily dose of medical marijuana. A Boxer’s skin cancer begins to disappear following topical applications of cannabis oil. A 12-year-old Lab mix diagnosed with liver and lung cancer regains his appetite and becomes more himself after his owner gives him a cannabis tincture purchased from a licensed medical marijuana dispensary.

These stories offer hope to pet parents with aging and/or sick dogs — hope that we can improve the quality of their lives and perhaps even extend them with medical cannabis. Even more hopeful is the fact that these aren’t isolated incidents, but rather, three in an ever-increasing narrative of companion animals and cannabis-assisted healing. Yet, despite marijuana now being legal in over 20 states, most veterinarians still won’t prescribe it. Why? Because, with the exception of Colorado, it’s illegal for veterinarians to even discuss (nevermind prescribe) cannabis for pets unless the state explicitly grants the vet the right to do so. So, even if vets believe that medical marijuana could relieve a dog’s pain, nausea or seizures, their hands are often tied. Physicians in those states are exempt from prosecution, but veterinarians don’t have the same protection.

Nonetheless, some have put their livelihoods at risk by challenging that prohibition, usually for the same reasons given by the late Doug Kramer, DVM, of Chatsworth, California: compassion, and to prevent owners from accidentally overdosing their animals in well-intentioned efforts to relieve their pain. In doing so, they’re not necessarily curing incurable conditions but rather, are helping their animals enjoy daily life with better appetite and less pain until age or disease ultimately catches up.

The Science Behind Cannabis and Dogs

There’s a scarcity of rigorous research on the topic, particularly for veterinary application, mainly because of the way cannabis has been culturally demonized in the past.

The first published research related to cannabis and companion animals appeared in 1899 in the British Medical Journal. Written by English physician and pharmacologist Walter E. Dixon, the article included Dixon’s observations on dogs’ response to cannabis. However, it would be almost 100 years before we understood where the response originated: in the endocannabinoid system (ECS).

All vertebrates, from sea squirts to humans, have an endocannabinoid system, which scientists estimate evolved more than 600 million years ago. This ancient system, unknown until the late 20th century, is named for the botanical that most dramatically affects it, Cannabis sativa. Cannabinoids are the ECS’s messengers. The system’s purpose is to maintain internal balance — to “Relax, Eat, Sleep, Forget and Protect.”

Marijuana, a complex botanical with more than 400 known natural compounds, contains at least 64 phytocannabinoids (plant-based cannabinoids). The two produced in greatest abundance are cannabidiol (CBD) and tetrahydrocannabinol (THC).

How do they work? According to the National Cancer Society, cannabinoids “activate specific receptors found throughout the body to produce pharmacologic effects, particularly in the central nervous system and the immune system.” The effects depend on the receptors to which they bind.

Dr. Robert J. Silver, DVM and veterinary herbalist of Boulder, Colorado, provides another way to look at it. “Receptors are like locks, and cannabinoids are like keys. They fit together perfectly. Once the cannabinoid connects to the receptor and ‘turns that lock,’ a series of actions in the cell membrane occur; these actions are responsible for some of the cannabinoid’s effects.”

In his book, Medical Marijuana and Your Pet, Dr. Silver notes that the ECS is unique in the world of neurotransmitters. Instead of releasing signals across a synapse (gap) in a forward direction, “the body’s naturally occurring endocannabinoids travel backward from the post- to the presynaptic nerve cell, inhibiting its ability to fire a signal. This is one way the ECS helps modulate and influence the nervous system.”

Research has revealed two distinct cannabinoid receptors, CB1 and CB2. As in other vertebrates, canine CB1 receptors are primarily found in the brain, but also appear in dogs’ salivary glands and hair follicles, while CB2 receptors are localized in canine skin, immune system, peripheral nervous system and some organs, such as the liver and kidneys.

Of the currently known cannabinoids, only one —THC — provokes a “mind-bending” response. CBD, on the other hand, has several well-documented biological effects, including antianxiety, anticonvulsive, antinausea, anti-inflammatory and antitumor properties.

Terpenoids, components that give plants their distinctive odors, also play a role, helping cannabis cross the blood-brain barrier and work synergistically. Dr. Ethan B. Russo, MD, associated with GW Pharmaceuticals in the UK, calls this the “ entourage effect.” In an article in the British Journal of Pharmacology, Russo notes that terpenoids may make a meaningful contribution to cannabis based medicinal extracts “with respect to treatment of pain, inflammation, depression, anxiety, addiction, epilepsy, cancer, fungal and bacterial infections (including methicillin-resistant Staphylococcus aureus [MRSA]).” The entourage effect also suggests that in general, the whole plant, with all of its phytocannabinoids, is likely to be most effective for medicinal purposes.

How to Treat Your Dog With Cannabis

Those who choose to treat their companion animals with medical marijuana generally give it to them in one of two ways: as an oil or as an edible — a food item made with marijuana or infused with its oil. While edibles intended for human consumption usually contain THC, those for dogs and cats more commonly use CBD from industrial hemp, strains of cannabis cultivated for non-drug use, which has almost no THC.

In 1996, California became the first state in the nation to legalize medical marijuana. It now has the largest legal medical marijuana market in the U.S. — not to mention an almost clichéd historical relationship with the herb — so it’s no surprise that many who are pushing the boundaries of its use with companion animals are based there.

Constance Finley, founder of Constance Pure Botanical Extracts (a Northern California legal medical cannabis collective), became involved in cannabis use with dogs when her 10-year-old service dog was diagnosed with hemangiosarcoma and given six weeks to six months to live.

Finley had been using cannabis oil herself to treat the effects of a debilitating autoimmune disease that began when she was in her mid-40s. The prescription medication she took almost killed her, she says, an experience that inspired her to set aside her long-held bias against marijuana and give it a try. The oil provided both pain and symptom relief, and Finley went on to study cannabis cultivation and the complicated laws around its use. She eventually developed proprietary blends of highly concentrated oils from multiple strains of cannabis, extracted with organic, food-grade solvents.

So, when her much-loved dog was struggling with cancer, she began giving the dog small amounts of cannabis oil, wiping it on her gums. Within days, the dog started to move around normally and eat; after three weeks of treatment with the oil, her vet could find no signs of the cancer. Unfortunately, she didn’t completely understand how cannabis worked; she figured her dog was cured and stopped using the oil. Within six months, the cancer was back, and ultimately it claimed her dog’s life.

However, the experience made her a believer in its value for companion animals. While to date, there’s been no dog-specific research on its medical use, Finley is confident that cannabis oil has a place in the veterinary toolbox. In her work with people, Finley says she has yet to see a conflict between conventional medications and cannabis, although anyone using it with dogs needs to be aware of the dog’s entire situation. It’s critically important, she says, that the dose be correctly titrated so the dog’s system isn’t hit with too much THC too quickly. She also notes that the effectiveness of an individual dog’s endocannabinoid system, not the dog’s weight, determines the dose. To establish the correct dose, it’s necessary to observe the dog.

A dosage protocol for dogs is one of the areas in need of study and standardization. In the mid-1970s, researchers found that dogs have a high concentration of CB1 endocannabinoid receptors in their hindbrain and medulla as well as other areas of the brain. This suggests that, in terms of compounds that include THC, dogs require less to get the desired effect. (One of the diagnostic signs of THC overdose is something called “static ataxia,” first described in the 19th century and unique to dogs. Dogs in this condition rock rigidly back and forth and drool, their muscles tense up, and their pupils dilate.) According to Dr. Silver, when it comes to dogs and medical marijuana, “The ratio of brain weight — and by extension, receptors — to body weight is not linear.”

Finley also observes that there are at least two myths about medical marijuana that need to be dispelled. First, that CBD is good and THC is bad; each has its uses, but for cancer in particular, she says, THC is the workhorse. Second, that hemp and cannabis are the same; they are different varieties or sub-species, and while CBD can be refined from hemp, she feels that cannabis provides oil that is more easily used by the body.

The Latest Legislation on Dogs and Cannabis

While many have seen positive outcomes, some veterinary professionals worry about people extrapolating from their own experiences with medical cannabis and giving dogs with health problems inappropriate amounts. “Sometimes public sentiment and activity get ahead of the scientific background, and that can be dangerous,” Barry Kellogg, senior veterinary adviser to the Humane Society of the United States, has said.

To date, the American Veterinary Medical Association has not taken an official position on the use of medical marijuana with animals but has provided a FAQ for members. The American Holistic VMA is the first, and so far only, veterinary organization to officially encourage research into the safety, dosing and uses of cannabis in animals. In 2014, the group released a statement that said in part, “There is a growing body of veterinary evidence that cannabis can reduce pain and nausea in chronically ill or suffering animals, often without the dulling effects of narcotics. This herb may be able to improve the quality of life for many patients, even in the face of life-threatening illnesses.”

According to Finley, the fact that the marijuana industry is unregulated has been part of the problem regarding access. But next year may be the tipping point. If California’s AB 266 is passed and the marijuana industry comes out of the shadows into effective regulation, particularly in terms of verifiable cannabinoid content and freedom from contaminants, the rest of the nation could follow. The state’s size, market potential, and trailblazing environmental and technology industries have historically influenced trends nationwide, and that dynamic is likely to drive the discussion in this case as well.

Veterinary professionals are generally in agreement that more study is needed. In a 2013 interview with R. Scott Nolen, Dawn Boothe, DVM and director of the Clinical Pharmacology Laboratory at Auburn University’s College of Veterinary Medicine, commented: “Veterinarians do need to be part of the dialogue. I can see a welldesigned, controlled clinical trial looking at the use of marijuana to treat cancer pain in animals. That would be a wonderful translational study, with relevance to both pets and their people.” (In translational research, laboratory science and clinical medicine combine their efforts to develop new treatments and bring them to market.)

Dr. Narda G. Robinson, DVM, director of Colorado State University’s Center for Comparative and Integrative Pain Medicine, agrees. In an email exchange, Dr. Robinson said, “There is a big gap that needs to be addressed between those who are already using hemp products and finding value for their animal and science-based practitioners who want to make sure that their patients are receiving safe and effective treatment. Research will help bridge that gap.”

What’s Next for Dogs and Cannabis

Clearly, veterinarians — our partners in keeping our animals healthy — need a voice in this debate. While interested in the herb’s potential, many are leery about trying it, not only because of the legal consequences but also, because there’s so little evidence-based information. On the other hand, pet parents who have found it useful feel that not including it in the vet-med repertoire is a missed opportunity.

Although the tide is slowly turning in its favor, the debate about the utility of medical marijuana and its related components for both humans and their pets is often mired in personal bias and opinion. Regardless of what position we take, it would seem that the best way to come to a resolution is to focus on the science. Controlled studies that determine cannabis’s therapeutic and toxic ranges in veterinary use and standardization of THC and/or CBD content have the potential to make a potent natural ally legally and safely available to our pups.

When Marijuana and Dogs Don’t Mix

As is often the case, if people consume something, dogs are likely to do so as well — either deliberately or on the sly. In states where marijuana is legal, an uptick has been reported in the number of vet visits for dogs who’ve ingested pot (as an FYI, they also show up in states where it’s illegal). Two dogs, a Schipperke and a Cocker Spaniel, died after  eating baked goods made with unusually large amounts of THC butter (as well as rich in chocolate and raisins, two known canine toxins). 

An ASPCA Animal Poison Control Center study lists the top five symptoms of marijuana toxicity as ataxia — loss of control of body movements — depression, vomiting, urinary incontinence and bradycardia, or abnormally slow heart rate. The takeaway? While death by pot isn’t common, it’s not unheard of. Dogs who get into a private stash or eat marijuana-enhanced edibles intended for people require immediate veterinary attention.