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Cannabis Toxicity in Dogs
Revised: July 31, 2018
Published: February 11, 2003

Image Courtesy Food and Drug Administration (FDA.org)

Cannabis, known by many names, needs little introduction: we all know it is a popular recreational plant smoked and consumed both legally and illegally by millions of people worldwide. What people smoke is the dried flowers and tops of the Cannabis sativa plant while "hemp" is a term generally reserved for the stems. It is diverted into assorted consumable forms while hemp is made into rope, canvas, and other materials. 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.

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.

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.

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