Editor’s note: Dr. Narda Robinson is the country’s leading authority on scientific integrative medicine (SIM). Dr. Robinson is a scholar, researcher and widely read author on evidence-based approaches to SIM.

Marijuana Plant

Both the promises and perils of medical marijuana (MMJ) point to the need for science-based education, regulation and research. Many of us living in Colorado, one of the first states to legalize the sale of marijuana for both medical and recreational purposes, find ourselves touched deeply on a daily basis by stories that both uplift as well as cause grave concern for our veterinary patients.

On the up side, marijuana appears to afford a “lifesaving” alternative for a daunting gamut of difficult-to-treat disorders, including intractable epilepsy (seizure disorders that drugs cannot control). For companion animals, even the American Veterinary Medical Association website carries testimonials favoring veterinary cannabis, in which caregivers attest to significant benefits in their animals, who were unresponsive or intolerant of mainstream pharmaceuticals.

Now that marijuana is becoming legal to buy for humans in a growing number of states, many are trying it on animals. But should you be administering it to your pet? Should your veterinarian?

Unanswered Questions

Because of the higher toxicity of tetrahydrocannabinol (THC) in dogs compared to humans, many cannabis products sold for dogs list cannabidiol (CBD) instead of THC as the main active ingredient. (THC is the substance in cannabis that typically makes human users high.) Websites selling CBD-predominant substances for dogs may claim that their products are “completely safe” but lack reliable research to back those claims. There are, in fact, many potentially helpful chemicals in the cannabis plant, but THC and CBD usually outnumber the rest, although amounts are dependent on the strain of plant. What that means is that the ratio of cannabinoids (i.e., chemicals in the cannabis plant) differs among plants based on their genetics. While the CBD in cannabis does not make someone “high” in the usual sense, it may benefit human patients with various medical problems, including Crohn’s disease, post-traumatic stress disorder and multiple sclerosis. CBD reduces pain, inflammation and anxiety as well as seizure activity. Research suggests that CBD has lower toxicity and higher tolerability than THC in both humans and non-humans. However, research has not yet established safe dosing guidelines for either population, partly because of highly restrictive federal laws that prohibit scientists from thoroughly investigating its effects.

A Deadly Uncertainty

Lacking rigorous scientific evidence, veterinarians cannot determine safe dosages and THC/CBD ratios of medical marijuana for dogs, cats and other animals. Veterinarians and owners are left relying on anecdotal reports, trial and error and companies’ claims. If the tolerable and safe dose, whatever that might be, is exceeded, an animal may land in the local veterinary emergency clinic, and there are no antidotes for THC poisoning. While many insist that marijuana overdoses cannot kill, the consequences of cannabis can indeed turn deadly in dogs as the result of THC overdose.

Dogs are most commonly exposed to cannabis through THC-laced edibles they find in the trash or in other opportune places, though some may ingest marijuana through purposeful exposure by their owners to tinctures, vapors and even homemade dog biscuits. The incidence of both intentional and unintended exposure is increasing as legalization spreads throughout the United States. As a cautionary tale, veterinary hospitals in Colorado have witnessed growing numbers of animals admitted for marijuana poisoning. Even before laws passed in Colorado allowing sales for recreational purposes, the number of dogs presenting with marijuana toxicosis quadrupled. Contributing factors beyond increased availability likely include a higher awareness among clinicians of the signs of poisoning, population shifts (e.g., marijuana “tourism” and immigration) and a greater willingness of clients to seek veterinary assistance for the condition.

Depending on the dose and route of administration, problems usually appear within 30 to 60 minutes after exposure. The ASPCA’s Pet Poison Helpline lists 12 common signs of toxicity ranging from coma to seizures and respiratory depression to hyperactivity.

Calls for Caution

Much more needs to be done to make marijuana safe not only for pets but for humans, too. To both pets and people, marijuana-laced foodstuffs are indistinguishable from their innocuous counterparts, raising the risk of accidental ingestion by children, animals and unsuspecting adults. The amount of THC cooked into the cookies, chocolates and other foods can also take those intentionally consuming the products by surprise. For example, shortly after consuming a marijuana cookie, a college student jumped to his death from a motel balcony. In another case, a Denver man shot and killed his wife after supposedly eating cannabis candy.

Those incidents underscore the urgent need for education, regulation and research. Unfortunately, federal restrictions on marijuana research have hampered investigation into both its value and dangers. Decade after decade, advocates of less restrictive marijuana laws have unsuccessfully petitioned the Drug Enforcement Administration (DEA) to rethink the listing of marijuana as a Schedule I addictive drug with no therapeutic value. Delisting cannabis would ease research restrictions and allow studies on safety and efficacy to move forward.

Today, inadequate oversight of the amount of THC that producers are putting into each serving of edible marijuana is resulting in injuries, as is the lack of guidelines for and availability of testing, labeling and protective packaging. Consumers are confused about how much to eat and whether one batch of cookies or candies will produce the same effects as the next, turning self-medicating into a game of wild guessing.

Safety Requires Study

As a result, Colorado is earning the reputation as the Wild West of medical marijuana. Tying the hands of researchers and clinicians who desperately want to begin research is federal law that bars them from studying the safety and effectiveness of medical marijuana. That is putting the safety of people, pets and the public in jeopardy. The cure? Remove restrictions on research so that scientists, physicians and veterinarians can study cannabis carefully and without risking their licenses, federal funding and/or freedom through imprisonment. Only then will we be able to safely determine the benefits and appropriate uses of medical marijuana for veterinary patients.

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