Cannabis (Marijuana) Intoxication in Cats and Dogs

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 of cannabis’ medicinal uses, 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 use for recreational purposes is more recent. In the 1970s, cannabis was criminalized in the US when it was labeled a Schedule 1 (Class I) drug. In the 1990s, individual states began legalizing cannabis for medicinal use, and more recently, 18 states have legalized it for recreational use. Legalization for recreational use in Canada occurred in 2018. As with any other medication, the increased accessibility to the drug has led to an increase in accidental exposure in pets.

"...increased accessibility to the drug has led to an increase in accidental exposure in pets."

How do cats and dogs become intoxicated?

Cats and dogs can become intoxicated by cannabis in various ways, most commonly by eating edibles (e.g., baked goods, candies, chocolate bars, and chips containing cannabis), 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 access to the drug 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 when compared to humans. A small amount of cannabis is all it takes to cause toxicity in cats and dogs.

Regardless of the method of exposure, accurate and complete information is imperative to treat the patient successfully. For example, ingestion of a 'pot brownie’ needs different treatment than inhalation because eating the brownie requires treatment for cannabis and chocolate toxicity, whereas inhalation may require additional treatment for respiratory irritation.

How does cannabis affect cats and dogs?

Like most drugs, the effects of cannabis are based on chemistry. The drug enters the body via inhalation or ingestion and interacts with and alters the brain’s chemical messengers, such as norepinephrine, dopamine, serotonin, and acetylcholine.

Everything that enters the body has to exit the body. THC is very lipid-soluble, which means that it is easily stored in the fatty tissue in the liver, brain, and kidneys before being eliminated from the body. THC is metabolized in the liver and the majority (65-90%) is excreted in the feces, while a small percentage (10-35%) is eliminated through the kidneys. The drug has to be metabolized and excreted for the effects to wear off.

How toxic is cannabis?

Cannabis is considered to have a high margin of safety for people; however, not all people, and certainly not all pets, follow a single pattern of intoxication. A small amount 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.

"A small amount may affect one pet more than another..."

Luckily, cannabis intoxication is seldom fatal. The average marijuana cigarette contains about 150 mg of THC. The minimum lethal oral dose of THC in pets is fairly high; however, deaths have been noted after ingestion of foods containing highly concentrated cannabis, such as medical-grade THC. In fact, fatalities were very rare until the development of medical-grade products.

What are the clinical signs of cannabis intoxication?

Many of the signs of intoxication are neurological. Pets may become wobbly and uncoordinated. They may be hyperactive or sleepy, disoriented, and/or very vocal. Their pupils may dilate, giving them a wild-eyed appearance, and they may drool excessively or vomit. They may also develop urinary incontinence (i.e., urine leakage). In severe cases, tremors, seizures, and coma can result.

Physical signs include slow or fast heart rate, altered blood pressure, and slowed respiration rate (breathing rate). Lethargy and increases or decreases in body temperature may also be observed. Fortunately, these side effects are usually short-lived but they can still be dangerous and make your pet quite miserable.

How is intoxication diagnosed?

Diagnosis is based on an accurate history and clinical signs. Although there are tests to determine the level of THC in the urine, the results take time, making them impractical. Human urine drug screening tests are quicker but are not dependable in pets. The diagnosis is made much more quickly, and treatment initiated, when responsible pet owners provide accurate information regarding the pet's exposure.

How is intoxication treated?

When a toxin enters the body, often the first line of defense is to get it out. 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. First, the signs of toxicity may manifest only after the drug has been absorbed, meaning it is already in the system. Second, 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.

"When a toxin enters the body, often the first line of defense is to get it out."

The second line of defense in cannabis toxicity involves providing supportive care until the effects of the drug wear off. Medications and supportive care to regulate your pet's heart rate, respiration, and body temperature are used if needed. Since your pet may be lethargic, with no desire to eat or drink, IV fluids can help prevent dehydration, support blood pressure, and maintain organ function. Anti-anxiety medications can minimize agitation. Gastrointestinal treatments may be needed for nausea or vomiting. To prevent self-trauma while your pet is disoriented and uncoordinated, confinement in a safe, comfortable space is helpful. Noise should be kept to a minimum to decrease sensory stimulation.

If cannabis is ingested with toxic or problematic substances, such as xylitol, chocolate, raisins, or foods containing a lot of fat, supportive care or additional treatments may be required to treat conditions associated with the ingestion of those substances.

The Bottom Line

The bottom line, when it comes to cannabis use and pets, is similar to that with other drugs in the home: Be careful. Keep all forms of cannabis, medical or recreational, out of reach of your pet. Consider storage in high cabinets or in locked drawers when not in use. 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.

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