Marijuana (or cannabis) refers to the dried parts of the Cannabis plant. Cannabis has been used since 500 BC as an 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.
"The increased accessibility to the drug has led to an increase in accidental exposure in pets"
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, 9 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.
How do cats and dogs become intoxicated?
Cats and dogs can become intoxicated by cannabis in various ways; by inhaling second-hand smoke, eating edibles (baked goods, candies, chocolate bars, and chips containing cannabis), or ingesting cannabis directly (in any form). 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.
"Accurate and complete information is imperative to treating the patient successfully."
Regardless of the method of exposure, accurate and complete information is imperative to treating 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 binds with specific neuroreceptors in the brain, altering normal neurotransmitter function. THC interacts with neurotransmitters such as norepinephrine, dopamine, serotonin, and acetylcholine. Humans and pets have two types of receptors in their bodies. One type, CB1, affects the central nervous system, and the other, CB2, affects the peripheral tissues. Although not all the pharmacologic mechanisms triggered by cannabinoids have been identified, it is thought that CB1 is responsible for most of the effects of cannabis.
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.
"Deaths have been noted after ingestion of foods containing highly concentrated cannabis such as medical-grade THC."
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 signs of cannabis intoxication?
Many of the signs of intoxication are neurological. Pets may become wobbly and uncoordinated. They may be hyperactive, disoriented, and 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.
"Side effects are usually short-lived, but they can still be dangerous."
Physical signs include low or elevated heart rate and 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 the 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 which inhibits vomiting. In life-threatening cases, the stomach may be pumped (gastric lavage). Activated charcoal may be administered every 6-8 hours to neutralize the toxin. Enemas are also used to reduce toxin absorption from the GI tract.
"Activated charcoal may be administered every 6-8 hours to neutralize the toxin."
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 the pet's heart rate, respiration, and body temperature are used if needed. Since the 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. To prevent self trauma while the pet is disoriented and uncoordinated, confinement in a safe, comfortable space is helpful. Noise should be kept to a minimum to decrease sensory stimulation.
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.