What is cannabis?
Cannabis (marijuana) refers to the dried parts of the Cannabis plant. Cannabis has been used since 500 BC as herbal medicine and for products such as rope, textiles, and paper. Today, cannabis is primarily used for medicinal or recreational purposes. Cannabis can be smoked like a cigarette, inhaled via vaporizers, or ingested via food and drink.
Cannabis contains more than 100 different chemicals (or compounds) called cannabinoids. Tetrahydrocannabinol (THC) is the cannabinoid that has the most psychoactive effects. It is also the compound responsible for some medicinal applications of cannabis, such as treating nausea and improving appetite in cancer patients. Other compounds, such as cannabidiol (CBD), have shown promise for medicinal use and do not have psychoactive effects.
While cannabis use is not new, its recreational use is more recent. In the 1970s, cannabis was criminalized in the U.S. when it was labeled a Schedule 1 (Class I) drug. In the 1990s, individual states began legalizing cannabis for medicinal use, and more recently, some states have legalized it for recreational use. Legalization for recreational use occurred in Canada in 2018. As with any other medication, increased accessibility to the drug has led to an increase in accidental exposure in pets.
How does cannabis affect cats and dogs?
Cannabis enters the body via inhalation or ingestion, then interacts with and alters the brain’s chemical messengers, such as norepinephrine, dopamine, serotonin, and acetylcholine. THC is very lipid-soluble, which means it is easily stored in the fatty tissue of the liver, brain, and kidneys before being eliminated from the body. THC is metabolized in the liver and most of it is excreted in the feces (65% to 90%), while a small percentage is eliminated through the kidneys (10% to 35%). The drug must be metabolized and excreted for the effects to wear off.
How do cats and dogs become intoxicated?
Cats and dogs can become intoxicated by cannabis in various ways, most commonly by eating things that include cannabis (e.g., baked goods, candies, chocolate bars, and chips) or by ingesting cannabis directly (in any form). Pets can also be exposed to second-hand smoke.
Most exposures are accidental, when curious pets discover the drug in the house or when they are present in the same room with a person smoking cannabis. Dogs have more cannabinoid receptors in their brains, which means the effects of cannabis are more dramatic and potentially more toxic in dogs. A small amount of cannabis is all it takes to cause toxicity in cats and dogs.
To treat a dog or cat with cannabis intoxication, it is imperative for your veterinarian to have accurate and complete information about how the pet was exposed. For example, ingestion of a pot brownie needs different treatment than inhalation because a dog who ate a pot brownie requires treatment for cannabis and chocolate toxicity, whereas a dog who inhaled cannabis may require additional treatment for respiratory irritation.
How toxic is cannabis?
Cannabis is considered to have a high margin of safety for people, but not all people follow the same pattern of intoxication. The same is true of pets. A small amount of cannabis may affect one pet more than another, so there is no official safe level of exposure. Differences in age, health status, and body size are some of the factors that can lead to toxicity differences.
Cannabis intoxication is seldom fatal. The average marijuana cigarette contains about 150 mg of THC, and the minimum lethal oral dose of THC in pets is fairly high. However, animals have died after eating foods that contain highly concentrated cannabis, such as medical-grade THC. In fact, fatalities were rare until the development of medical-grade products.
What are the clinical signs of cannabis intoxication?
Many of the signs of cannabis intoxication are neurological:
- Wobbly and uncoordinated movements
- Hyperactivity or sleepiness
- Disorientation
- More vocal
- Dilated pupils (wild-eyed appearance)
- Excessive drooling
- Vomiting
- Urinary incontinence (i.e., urine leakage)
- Tremors, seizures, or coma in severe cases
Physical signs include:
- Slow or fast heart rate
- Altered blood pressure
- Slowed respiration rate (breathing rate)
- Lethargy is possible
- Increases or decreases in body temperature are possible
Fortunately, these side effects are usually short-lived, but they can still be dangerous and make your pet miserable.
How is intoxication diagnosed?
Diagnosis is based on an accurate history and clinical signs. There are tests to determine the level of THC in the urine, but the results take time, which makes them impractical. Human urine drug screening tests are quicker, but they are not dependable in pets. The diagnosis can be made much more quickly, and treatment can begin sooner, if you can provide accurate information regarding the pet's exposure.
How is intoxication treated?
If the toxicity is discovered shortly after ingestion, your veterinarian may induce vomiting to prevent further absorption of the toxin. Two factors may interfere with this early defensive strategy: the signs of toxicity may manifest only after the drug has been absorbed, meaning it is already in the system, and cannabis has an anti-emetic effect that inhibits vomiting.
In life-threatening cases, the stomach may be pumped (gastric lavage). Activated charcoal may be administered every six to eight hours to neutralize the toxin. Enemas are also used to reduce toxin absorption from the gastrointestinal tract.
Treatment also involves giving supportive care until the drug’s effects wear off, including:
- Medications and supportive care to regulate your pet's heart rate, respiration, and body temperature
- Intravenous (IV) fluids to help prevent dehydration, support blood pressure, and maintain organ function
- Anti-anxiety medications to minimize agitation
- Gastrointestinal treatments for nausea or vomiting
- Confinement to a safe, comfortable space while your pet is disoriented and uncoordinated (reduces self-trauma)
- Minimal noise to decrease sensory stimulation
If your pet ingests cannabis along with other toxic or problematic substances, such as xylitol, chocolate, raisins, or foods containing a lot of fat, they may need additional supportive care or treatments for conditions associated with the ingestion of those substances.
How can I prevent cannabis intoxication in my pet?
To prevent cannabis intoxication, treat cannabis the same as any other drug in the house.
- Keep all forms of cannabis out of your pet’s reach, whether they are medical or recreational.
- Consider storing cannabis in high cabinets or locked drawers.
- Keep pets in a separate and well-ventilated room, away from second-hand smoke.
Remember that pets have a good sense of smell and will be tempted to eat candies, chips, chocolates, and cannabis directly, if accessible. If you notice suspicious behavior in your cat or dog and cannabis exposure is a possibility, take your pet to your veterinarian or the nearest emergency veterinary hospital for treatment.
