Veterinarians Caution: Medical Marijuana Exposure in Pets

September 7, 2017

Marijuana has been prominent in pet news recently due to the rise of medical marijuana use in people. It is important for you to know about these products since the probability of your pet becoming exposed is increasing.
The effects of using medical marijuana in pets is not well studied to date. 
It appears dogs are proportionately more sensitive to the active compounds in marijuana than people. An American study in 2012 by Meola and others reported increased rates of toxicity seen in dogs living in Colorado, a state with recent legalization of marijuana. In fact a four-fold increase in toxicities was reported between 2010 and 2015.
In small dogs, excessive intake can easily result in signs of toxicity, as listed below. Cats are not immune to toxic side effects, but are much more selective in their food intake. Cats generally avoid eating garbage, scavenging butts on walks around the block, or table or counter surfing, and they lack a sweet tooth so we do not see them take in “pot” products like dogs do.
Though, no pet is immune to respiratory irritation from side-stream smoke or purposeful cannabinoid product administration, with possible inadvertent (or, very rarely intended) overdose or illness resulting. 
Signs of excess cannabis exposure in pets include:
  • Salivation
  • Sleepiness
  • Fast or slow heart rate
  • Depression
  • Dilated pupils
  • Bloodshot eyes
  • Low body temperature
  • Wobbling, pacing and agitation
  • Vocalizing
  • Sound or light sensitivity
  • Inappropriate urination
  • Vomiting 

Where does Marijuana come from?

Cannabis sativa L plants are the source from which recreational and most medical marijuana products are prepared. Preparation includes drying of leaves and flowers. Different types of prepared marijuana have a range of levels of THC (tetrahydrocannabinol), which is the well-known psychoactive compound. “Marijuana” refers to products containing any bioactive cannabinoid compounds, of which THC is just one example. 
Marijuana can be broke down into three classes:
  1. Recreational: The plants can be smoked or vaporized from the dried leaves and flowers, or used in baking and other oral preparations for humans. This class has the highest risk for pet toxicity due to high THC levels.
  2. Medical: These products contain moderate to high CBD levels (cannabidiol, another cannabinoid; a non-psychoactive compound), and minimal to moderate THC. These medicinal products are used for antibacterial, gut soothing, and anxiety soothing treatments in people. They are also used for anti-nausea and vomiting, anti-oxidant, pain relieving, and anti-itch properties in people in addition to the psychological effects. Medical marijuana may be prescribed for cancer, osteoarthritis, chemotherapy, epilepsy, and certain inflammatory bowel conditions in humans.  There are many plant cannabinoids (80-113 different types reported), and CBD is the main cannabinoid selected for in most medical marijuana products.  Human medical products do not emphasize psychological effects (THC), but rather promote proposed medicinal effects (CBD).  Strong psychoactive effects of THC are not generally desired for human medicinal use. Some of these products contain enough THC to produce toxicity in pets. 
  3. Hemp: A different subspecies, industrial hemp, has been cultivated for centuries for its rich fibre. It has been used in textiles and paper. Hemp tends to be the plant type used for pet “medical cannabis”; most of those products are hemp oil, tincture, or hemp powder. Some pet hemp oil products are available for legal purchase in Canada and Europe because the products contain either none or just a trace of THC, and they are derived from legal hemp plants.  Currently, pet hemp products are being promoted as aids for itching, anxiety, nausea, poor appetite, seizures, cancer, digestive problems, inflammation, immune disease, and reduced mobility due to joint pain in animals. Hemp products do not get the pet “high”, but effective and safe dosages have not been studied. Hemp is very low in THC and contains minor to moderate CBD levels; there is currently insufficient research data to know rates or thresholds for toxicity.

Veterinarians are not allowed to prescribe any of these products for pets

Certain legal hemp products may be useful in pets according to some experts, but veterinarians are not allowed to prescribe any of these products for pets. In fact, the College of Veterinarians of Ontario (CVO) reminded its veterinarians that: "There are currently no *CBD products approved by Health Canada and therefore no legal pathway to obtain these products.”  ("CBD" refers to cannabidiol).
Pet owners who intend to administer these products without veterinary consultation, as some have done when traditional medicines have failed, are doing so even though no proven safe and effective doses have been published. Due to lack of sufficient evidence about effective, safe dosage and optimal frequency of administration in dogs and cats, owners should not dose their pets with any type of marijuana product. The only information we know for certain at this time is that dogs have a higher sensitivity to the same dose of cannabinoids when compared proportionately to people. 
Read More About Excessive Marijuana Exposure in Your Pets
Further research is recommended to understand the safety and effectiveness of medical marijuana in veterinary medicine. For now, marijuana of any type is not approved for medicinal use in animals, and giving products to your pet may have unknown side effects and unproven effectiveness. Especially, exposing them to THC-rich recreational marijuana could put them in a life-threatening medical crisis. 
Kathleen Cavanagh BSc DVM MET
CVMA Consultant Online Editor
Jennifer Kyes, DVM, DACVECC (Critical Care) 
Specialist Editor  
September 7, 2017