For decades, stereotypes about people high on marijuana have included images of unmotivated, relaxed (maybe even sleepy) people sitting on couches, eating potato chips and ice cream. Sadly, the picture is not-so-innocent when animals are exposed to marijuana, and that is happening more frequently.

While marijuana remains illegal under federal law, 33 states now have laws that legalize it in some form. In the 2018 election, Michigan citizens voted to legalize recreational marijuana, which made Michigan 1 of 10 states (plus Washington, D.C.) to allow marijuana for recreational use. With increased legal access to marijuana and marijuana-infused products for people (both medicinal and recreational), veterinarians are seeing an unfortunate increase in cases of marijuana poisoning in pets. In the past several years, Pet Poison Helpline has seen a 448 percent increase in marijuana cases.

Marijuana is toxic to cats, dogs, and horses. Animals process many compounds differently than humans do, and as a result, many foods and medications that are safe for us are not safe for them. These include acetaminophen, ibuprofen, raisins and grapes, macadamia nuts, chocolate, and the artificial sweetener xylitol.

The psychoactive compound in marijuana that makes people high, THC (delta-9 tetrahydrocannabinol), is toxic to pets. THC and CBD (cannabidiol) are the most commonly known and studied cannabinoid compounds in marijuana, but more than 500 chemical compounds and 100 cannabinoids have been identified in marijuana (cannabis) plants so far. The amount of THC and CBD can vary widely from plant to plant. CBD is not psychoactive, and is thought to be non-toxic, or to have limited toxicity. Recent research is providing more data about the pharmacokinetics, safety, and efficacy of CBD in pets. However, products that claim to contain only CBD can be contaminated with THC, so there is still some risk in using CBD products for pets.

Marijuana-infused edibles for people are made with oil or butter used to extract THC from the plant material. As a result, these products often contain higher levels of THC than plant material (buds, leaves, and stems) and pose a greater risk for poisoning pets. In addition, they may contain chocolate or other substances that also are toxic and/or that could make an animal sick.

Because THC is toxic to pets, animals that are accidentally or intentionally exposed are not just high or stoned. They don’t simply need to “sleep it off.” They should be taken to a veterinarian for an examination and/or for supportive care.

If animals eat or inhale THC (even second-hand smoke can affect pets), common signs that owners may notice include inactivity; incoordination; dilated pupils; increased sensitivity to motion, sound, or touch; hypersalivation; and urinary incontinence. A veterinary exam can reveal depression of the central nervous system and an abnormally slow heart rate. Less common signs include restlessness, aggression, slow breathing, low blood pressure, an abnormally fast heart rate, and rapid, involuntary eye movements. Rarely, animals can have seizures or become comatose. Death is extremely rare. Signs can last for less than an hour or for several days, depending on the amount of THC to which the animal was exposed.

One of the reasons that animals experiencing these outward signs of poisoning should be taken to the veterinarian is that many of the common signs of THC poisoning are similar to the signs of antifreeze poisoning, which is extremely dangerous. In those cases, an antidote can be given early, but if the antidote is not given in time, antifreeze poisoning is almost 100 percent fatal without aggressive treatment.

Owners who know or suspect that their pet has eaten or was exposed to marijuana (plant material, edibles, oils, prescription medications, and/or smoke) should be completely honest with their veterinarian. The doctors, technicians, and staff at the veterinary clinic only care about the well-being of the pet. Being honest and open helps them provide the best and most appropriate care, and avoid unnecessary tests or treatments.

If exposure cannot be confirmed, the veterinarian must consider other diagnoses. These include alcohols (including antifreeze), opioids and other drugs, and rodenticides.

While diagnostic laboratories, such as the Michigan State University Veterinary Diagnostic Laboratory, can test for marijuana (and other drug or toxin) exposure, those tests take days to run, and animals have typically recovered by the time results are available. Urine tests widely available for human use often have false negative results when used on animals for a variety of reasons. One reason is that dogs process THC differently than people, and their urine contains different compounds that tests designed for people do not detect.

Recommended tests might include X-rays (depending on what was eaten) and general blood tests to establish a baseline, rule out other conditions, and to monitor the animal’s response to supportive care. Supportive care may involve inducing vomiting (only if a toxic dose was eaten, and if exposure was very recent, and the animal is showing no signs), using activated charcoal, providing IV fluids, warming or cooling therapy (hypothermia is common), and general nursing care. Medications are needed for animals experiencing more severe signs, such as agitation, tremors, seizures, or slowed heart rate.

Marijuana products (plants, edibles, lotions, oils, etc.) in the home should be kept securely away from pets, just like alcohol or medications. Pet owners should be particularly vigilant about how they store and use products with concentrated levels of THC. If owners suspect poisoning or notice signs of potential poisoning in their pets, they should call their veterinarian or a pet poison hotline immediately. Emergency veterinary treatment may be needed. The Michigan State University Veterinary Medical Center is open 24 hours a day, 365 days a year.