Marijuana toxicity can pose health problems for pets

The first time I treated a cannabis overdose was when a man brought in his beautiful, new nine-week-old puppy. The roly-poly bundle of joy had ripped open a baggy and gorged on the entire stash. The man was sick with worry and rightly so — marijuana toxicity can be very serious in pets.

The recent legalization of recreational cannabis will bring some changes to Canadian society. With it come some particular issues related to animal health.

The first is the concern about overdoses in pets. Legalization will create more openness with having and using cannabis, and with more pot lying around, the greater the chances of a pet accidentally eating it.

Dogs are at greater risk compared to cats due to their curiosity and often unscrupulous eating habits.

After Colorado legalized recreational cannabis use there were four times more calls to a pet poison information line about marijuana toxicity.

Deaths from cannabis overdose are rare in dogs because the lethal dose is large (more than three grams per kilogram). Lethal cases tend to occur in dogs that consume higher-concentration oils and edible products. Exposed dogs have a range of clinical signs including excessive salivation, dilated pupils, depression, vomiting, urination, low body temperature and tremors. With very high doses, the clinical signs are much more serious, including seizures, agitation, inco-ordination and rapid breathing or heart rate.

Treatment involves supportive care because there is no antidote. Keeping cannabis products, especially oils and edibles, safely stored is key to prevention.

The second health consideration is the use of marijuana for the treatment of medical conditions in animals. As with the use in human medicine, there is a huge lack of scientific knowledge about its therapeutic uses. The strict controls that were previously in place prevented research from progressing.

That isn’t to say that people and potentially some pets may benefit from cannabis, but we don’t yet have the evidence to inform science-based recommendations. With legalization, research on the use of medical marijuana for people and pets can occur and will greatly advance our understanding of its benefits and risks.

For now, veterinarians cannot legally prescribe cannabis for animals. The laws that permit human use for medical purposes do not extend to vets or their patients.

Beyond the legal issues, there is little scientific evidence to support its use. There needs to be well-designed, randomized clinical trials to support that there is a benefit to treatment.

We also need more information about its safety, including the risk of long-term effects. In an example of the types of studies we need, a recent randomized clinical trial in dogs at Cornell University in New York investigated the use of cannabis oil in dogs with arthritis. Dogs were randomly assigned to receive either the treatment or a placebo oil with the owners and vets blinded to their treatment type. After one month, the dogs were given a two-week break and then switched to receive the opposite oil. Both vets and owners found a significant decrease in pain and an increase in activity when dogs received the cannabis oil compared to the placebo, suggesting a substantial clinical benefit for arthritis treatment. Owners did not see any side effects.

This study, which was published in Frontiers in Veterinary Science, shows that the use of medical marijuana in animals has promise. It also provides an excellent example of the type of high-quality studies needed to make informed treatment decisions.

According to the Alberta Veterinary Medical Association, another issue hindering research and use in animals is the products themselves. There is a variety of active compounds between plant strains. The way plants are stored and processed also affects potency. Collectively, this makes it very difficult to study medical marijuana because it is challenging to standardize the dose. It will also be an issue to overcome if the laws change to allow vets to prescribe its use in animals.

As for the puppy, I administered a medication to make her vomit before a high set in. I also weighed what came up to estimate her dose compared to what she had eaten. The puppy went home a bit subdued but made a full recovery. And I’m sure her owner found a more secure place for storing his weed.

Dr. Jamie Rothenburger, MVetSc, PhD, DACVP, is a veterinarian who practices pathology and is an assistant professor at the University of Calgary’s Faculty of Veterinary Medicine. Twitter: @JRothenburger

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