Hemp plants are legal to grow so long as they contain less than 0.3% THC, the chief recreational cannabinoid of Cannabis.

Cannabinoids are the active Cannabis-derived substances that have pharmaceutical activity. Over 480 relevant substances have been isolated. The amount of each contained in a sample of Cannabis will depend on the subspecies of plant, how it has been dried, the time of year it was harvested, the age of the plant, and other factors.

The body has natural cannabinoid receptors in neurologic cells as well as in immune cells. Effects of cannabinoids are only partly through these receptors. Our bodies make natural cannabinoids as well. Cannabinoids can have assorted pharmaceutical effects: reduction in nausea, induction of euphoria, interference with short term memory and ability to filter insignificant information, increased appetite, antioxidant effects, anti-inflammatory effects, antibacterial effects, and more.

The psychoactive chemical that makes a recreational drug is delta 9-tetrahydrocannabinol, more commonly called THC. It is typically 1-8% THC while hashish, made from the flowering tops of the plant and their resins, can contain up to 10% THC.

Another cannabinoid chemical is cannabidiol, commonly referred to “CBD”, which is not considered recreational and is of a more medicinal nature. Cannabidiol has been used in human medicine to mitigate anxiety, improve appetite, relieve nausea, control seizures of certain types, and assist in sleep disorders. Assorted CBD products are available for human use both online and through dispensaries. Some products are marketed for pet use though is, with rare exception, not legal (see section below).

Cannabis plants have been used medicinally for thousands of years. Cannabis was made illegal in the U.S. first in 1911 and was ultimately listed in the Controlled Substance Act of 1970 as a schedule I substance, meaning that it has no accepted medical use. In recent years, attitudes have changed and medical use first became legal in 1996. As medical uses for cannabinoids are being explored and more states legalize medical and recreational Cannabis, exposure of pets to THC has increased dramatically, particularly in dogs.

Cannabis Intoxication in Dogs

The usual pet toxicity case involves a dog that has inadvertently eaten it. In dogs, clinical signs typically begin 30 to 90 minutes after it has been eaten. Because THC is stored in the body’s fat deposits, the effects of ingestion can last for several days.

Symptoms

Signs include: incoordination and listlessness along with dilated pupils, slow heart rate and sometimes urinary incontinence. A characteristic startle reaction has been described where the pet appears drowsy and even may begin to fall over but catches balance. Cannabis toxicity can look similar to intoxication with numerous other sedatives, but the most serious consideration is anti-freeze poisoning, which looks similar in its early stages and is usually fatal if not diagnosed early.

The dog in this video stole a Cannabis-containing baked good from the owner. Note the characteristic startle response and balance issues.

It is important for all the relevant exposure information to be given to the veterinarian if the pet is to be helped; veterinarians are not obligated to report anything to local police. If you know Cannabis was involved in an intoxication, you must tell the attending doctor. Obviously this goes for other recreational drugs as well.

Urine testing similar to that done with humans can be done in dogs to make the diagnosis of Cannabis intoxication. Test kits are available at most drug stores and can include assays for a number of recreational drugs. A relatively large volume is needed to run these tests, so if the pet is small this may be difficult to obtain, particularly in a female. Also, false negatives are common when the THC urine test is performed on pet urine; a positive is confirmatory but there are many false negatives as the metabolites relevant to the test are different between dogs and humans. In most cases, the diagnosis is made based on the clinical presentation of the dog plus history of Cannabis exposure.

Treatment

If less than 30 minutes have passed since the Cannabis has been eaten, it may be possible to induce vomiting, but after symptoms have started the nausea control properties of the cannabidiol make it difficult to induce vomiting. Furthermore, if the patient is extremely sedated, vomiting can be dangerous as vomit can be inhaled and cause a serious and deadly aspiration pneumonia.

Activated charcoal is a liquid material used in treating poisoning. Activated charcoal is given orally and as it passes from one end to the other, toxins are trapped in the charcoal so that when the charcoal passes from the patient, the toxins pass too. This technique of detoxification may be used to treat Cannabis toxicity if ingestion has occurred recently.

Fluid support and keeping the patient warm may also be needed. If the patient has lost consciousness, then more intense observation and support is needed. The chance of fatality is statistically small but possible. In most cases, the patient can simply be confined to prevent injury until the THC wears off.

Medical Cannabis Products for Pet Use

As medicinal Cannabis becomes legal and commonplace in the U.S., many people wish to try products on their pets. Some cannabinoid companies even make products packaged for pet use. There are several reasons to be cautious about using these products. Here are some to consider:

• The FDA, being a federal agency, does not recognize any of these products as legal and thus their manufacturers are not required to show them to be effective. Similarly, they are not required to actually contain the amount of active ingredient they claim to have. (In several studies, numerous CBD oils were found to contain no CBD whatsoever. See this link for details.
  
• An effective cannabinoid dose quickly becomes ineffective as the body becomes tolerant to the medication and more is needed to generate the desired effect. A cannabinoid that seems to create a good effect at first, is not going to be useful later on. How long does it take for a dose to become ineffective? No one knows but there was a study showing that with regular use, a toxic dose is no longer a toxic dose after one week.
  
• According to the American Veterinary Medical Association, “under current federal and state law, veterinarians may not administer, dispense, prescribe or recommend cannabis or its products for animals.” None of the laws allowing for legalization of Cannabis use extend to pet use. Pet use of cannabinoid is not legal with only a few exceptions.
  
• Research involving cannabinoid use in pets in sparse. Until research gets underway and more is published, proper regimes for pets are not available.
  
• While these products are most likely safe and readily available, none of them have been formally investigated for pet use in the same way that FDA-approved medications have been. If there is a product that actually has been proven effective and is available through your veterinarian, you may get better results from a more mainstream treatment plan.

Cannaboids will interact with other medications so if you plan to use any of these products, be sure your veterinarian is aware that you are doing so. Keep any medicinal or recreational products out of the reach of pets and children.

THC has psychoactive effects on the brain, making it popular for recreational use. Psychoactive substances affect the mind or behavior and work on the nervous system, altering mood and feeling and making marijuana popular for recreational use. However, because THC affects many other body systems, it also has many medical uses. In fact, marijuana has been safely used medically for centuries.

In the United States, the Drug Enforcement Agency (DEA) has classified THC as a Schedule 1 drug. Schedule 1 drugs have no currently accepted medical use and a high potential for abuse. Despite this classification, almost all states have legalized marijuana for either recreational or medical use.

Another cannabinoid found in the Cannabis sativa plant, called cannabidiol (CBD), is also popular, but because it does not have psychoactive effects, its popularity is primarily because of medical benefits.

Marijuana contains at least 1% THC, although this percentage depends on what part of the plant is used and how it is processed. Products made from marijuana seeds contain little or no THC, but products made from the plant’s buds or flowers can contain up to 10% THC. In recent years, selective plant breeding has produced levels of THC up to 50%.            

The United States government has legalized a different Cannabis sativa plant called industrial hemp. Hemp can contain no more than 0.3% THC, but it can contain larger amounts of a second phytocannabinoid, cannabidiol or CBD. Because it contains little THC, the DEA does not control hemp or its products, and they are not considered illegal by the federal government. Because it is not illegal, many dietary supplements containing CBD are now being marketed for medical use in animals.

How It Works

The phytocannabinoids THC and CBD in Cannabis sativa work through the body’s natural endocannabinoid system (ECS). (Endo means self.) The chemicals in the ECS interact with the cannabinoid receptors found throughout the body, helping to regulate physiologic functions, and may be involved in different diseases. Using drugs to influence this system may help in the treatment of disease.

The medical effects of THC and CBD differ because they interact differently with the endocannabinoid system. 

In human medicine, CDB has been used to treat anxiety, improve appetite, relieve nausea, control certain types of seizures, and assist in sleep disorders. In animals, pain associated with osteoarthritis and seizures associated with epilepsy are common uses of CBD.

CBD and Supplements

CBD is not psychoactive like THC but may have medical benefits.

CBD is not a scheduled drug by the DEA and is an added ingredient in dietary supplements sold online, at dispensaries, and available over the counter. THC and CBD are also available by prescription, and your veterinarian may prescribe one or the other for treating your pet, most commonly for pain management. 

The difference between supplements and prescription drugs is that unapproved products like supplements are not regulated, nor are they assessed for consistency. Supplement labels may inaccurately list the amount of CBD in the product. More importantly, supplements may contain chemicals such as synthetic cannabinoids that are not listed on the label but may be dangerous to your pet.

In general, marijuana is safe. People are generally exposed to higher amounts of THC than pets because people more commonly smoke, rather than ingest, marijuana. THC that is ingested (for example, marijuana cookies) is removed mainly by the liver before it can get into the blood. THC that is inhaled bypasses the liver, and most of it enters the blood.

Toxicity in THC vs CBD

Because of its psychogenic effects, products containing THC are more likely to cause clinical signs that look like toxicity in dogs or cats. However, in contrast to marijuana or THC, products containing CBD have not been associated with significant toxicity or side effects in dogs. Toxicity or side effects to cannabis most likely reflect the effects of THC rather than CBD but are rarely lethal.

In cases in which side effects were reported with a supplement containing CBD, the supplement also contained THC. Even then, the side effects involved the gastrointestinal tract (vomiting, diarrhea) and were not severe.

An exception is those products that contain synthetic cannabinoids or if other drugs have been unknowingly added. These products can be life-threatening. This is another reason that it is important to bring the actual product to your veterinarian.

Different cannabinoids have varied effects. Each cannabinoid may reach a different area of the body. Responses to CBD among animals may reflect the differences in individual endocannabinoid systems.

Keep any medicinal or recreational products out of the reach of pets and children.

Signs of Marijuana Toxicity in Pets

The legalization of marijuana has led to increased reports of toxicity in dogs and cats. Most pet exposure to marijuana occurs after eating homemade baked goods containing the dried marijuana plant (about 70%), followed by eating the plant itself (about 10%).

For marijuana toxicity to occur, the pet must eat a large amount of marijuana. The amount of marijuana plant necessary to cause death in a dog or cat has not been determined. However, the least amount that has ever been associated with signs of toxicity is 3 to 9 g per kg of animal weight (about 7 to 20 g per lb.). For comparison, the average marijuana cigarette generally contains only about 0.5 to 1 gram of plant material. 

A problem with dogs ingesting marijuana in baked goods such as brownies or cookies is that they often contain chocolate, which is also toxic to dogs. Baked products may also contain concentrated forms of marijuana butter or oil. Another possible reason for marijuana toxicity in dogs is that marijuana may contain unsafe, illegal substances such as other drugs or synthetic cannabinoids. In cases where death has been reported in dogs, the marijuana most commonly was in baked goods. Chocolate may contain the sugar substitute xylitol, a substance that is toxic to dogs. 

After ingestion, the time it takes for clinical signs to occur and how long it takes for the pet to become normal again depends, in part, on how much marijuana and what else might have been ingested. Clinical signs can appear as early as 30 minutes after exposure but may take up to two hours to occur. After ingestion, pets may become normal again in as little as a couple of hours, but more often, it takes 24 to 72 hours for pets to return to normal.

A common clinical sign of marijuana toxicity is loss of urination control. Because this sign does not occur with other toxins, it helps with the diagnosis.

Other common clinical signs of toxicity include:

•  lethargy or depression;
•  difficulty walking or standing; 
•  increased sensitivity to motion, sound, or touch (easily startled); and
•  salivating (drooling).

Rarely, the pet may become aggressive. With the most severe toxicity, seizures may occur, or the pet may become comatose. Pets that already have illness may be more likely to become ill. Clinical signs in these pets may depend on what other illnesses they have.

Compared to humans, a dog has many cannabinoid receptors around the brain that help with balance. When dogs ingest a large amount of THC, they may become uncoordinated and unable to stand. This THC side effect in dogs is not likely to occur with CBD or in other species.

Diagnosing marijuana toxicity can be difficult. It is important that your veterinarian be given any information that might help with identifying the cause of the clinical signs. Bringing the actual product your pet was exposed to with you to the clinic can help. There is no risk to you as the pet owner because your veterinarian is not required to report toxicity to local law enforcement. 

In humans, urine tests are used to detect chemicals metabolized in urine from THC. However, animals do not make these metabolites, so these types of urine tests are not helpful.

Treatment for Toxicity

Diagnosis and treatment of marijuana toxicity depend on a well-informed veterinarian.

There is no specific antidote for marijuana toxicity. Treatments are given help to control the clinical signs. This might include fluids or drugs to control vomiting and, for severe toxicity, antiseizure medications.  

Usually, the patient is sent home after a physical examination. The pet can be kept in a confined space and monitored until the effects wear off. However, more intense in-hospital observation and support are needed if the patient has lost consciousness.

If less than 30 minutes have passed since the Cannabis has been eaten, it may be possible to induce vomiting. However, the pet may inhale stomach contents, particularly if it is acting sedated. This option may be necessary if the pet ingested a life-threatening toxin.

In more severe cases of toxicity, your veterinarian may give activated charcoal orally. This is a liquid that helps to bind ingested toxins. The toxin passes along with the charcoal when the pet defecates. However, this should not be given to patients that are sedated.

Cannabinoids might interact with other medications. For example, they may cause other medications to leave the body more slowly. It is important to notify your veterinarian if your pet is receiving cannabis or any supplement. 

The ASPCA National Animal Poison Control is available 24 hours a day at 888-426-4435. Expect an initial consultation fee of around $100.00 and additional follow-up is at no charge. You will be assigned a case number your veterinarian can use to communicate with a toxicology specialist before beginning treatment.