Marijuana (Cannabis sativa) Intoxication


Marijuana (Cannabis sativa) is the most common illegal drug in the United States. Moreover, its use is reportedly on the rise – a status that’s presumably fueled by its emerging role as a legitimate medicinal drug along with its recent legalization for recreational use in Washington and Colorado. As such, it makes sense that its accessibility to pets – and its resultant toxicity – would be on the ascendance as well.

Marijuana is available as a dried plant that can be burned and smoked or inhaled as a vapor. It’s also increasingly available in edible formats, especially in states where its medicinal and/or recreational consumption has been legalized. Edible forms of marijuana are typically sweetened and flavored, making them more attractive to pets.

Dogs are considered much more likely to ingest toxic quantities of marijuana than their feline counterparts. This is likely due to the fact that cats are not as motivated to ingest edible marijuana products as dogs are. It bears noting, however, that dogs will often consume the dried plant quite readily and cats – especially kittens – may find themselves exposed after playing with it.

It’s also the case that some pet owners will intentionally expose their pets to marijuana with either recreational or medicinal intentions by blowing smoke or vapor in their faces or by offering them edible products containing the drug.

Despite its increasing cultural acceptability, pet owners are often reluctant to offer information about their pets’ condition, frequently confounding the diagnostic process. In spite of the fact that veterinarians are not required by law to report illegal activity such as drug possession, the subject of marijuana exposure nonetheless remains a touchy one between veterinarians and their pet-owning clients.

Marijuana contains a compound called THC (delta-9-tetrahydrocannabinol) that leads to the release of several neurotransmitters (acetylcholine, dopamine, norepinephrine and serotonin). The sudden release of these neurotransmitters into the brain is deemed responsible for the drug’s effects: lethargy and apparent confusion progressing to difficulty standing or walking, and profound sedation (if larger doses are received).

The effects of marijuana are clearly dose-dependent. Some doses may even prove therapeutic to pets. It’s important to note that some drug companies have already begun investigating the use of marijuana as a therapeutic drug for pain, nausea and appetite stimulation in pets.

Symptoms and Identification

The signs of marijuana intoxication are not dissimilar to those we observe in humans who have been exposed to excessive quantities of the drug.

Clinical signs of intoxication may include one or more of the following (in order of typical progression):

  • Lethargy or depression

  • Change in mentation (altered cognition)

  • Glassy-eyed appearance

  • Stumbling gait or loss of balance (ataxia)

  • Dilated pupils

  • Inability to walk

  • Nausea and vomiting

  • Recumbence

  • Profound sedation

Alternatively, in about 25% of patients, agitation and excitement may ensue. Unfortunately, this reaction to the drug includes changes in heart rate, tremors, and seizures.

The typical onset of clinical signs begins within thirty to sixty minutes after ingestion or exposure, as in humans. Interestingly, however, the effects of marijuana may last for longer periods of time in dogs and cats – up to thirty-six hours in some cases.

Again, it’s important to note that the effects of marijuana are dose-dependent. For example, while marijuana is often taken medicinally to relieve nausea, large amounts of these same neurotransmitters in the brain can lead to nausea and vomiting (in pets and humans, alike).

Despite the apparent severity of some of its effects, death due to marijuana toxicity is considered extremely rare in pets. Complications from concurrent exposure to other drugs, such as theobromine in chocolate (some edible marijuana products contain chocolate), and certain recreational drugs (cocaine, ecstasy, etc.) may be a factor in exposure to marijuana.

Diagnosis of marijuana intoxication is far more difficult in animals than for humans for a variety of reasons: Not only are pet owners reluctant to admit their pets have had access to illegal drugs, testing for these drugs is not considered as accurate as it is in humans. False negative test results are common.

The following tests and procedures may be undertaken as part of the diagnostic process:

  • Physical examination

  • Neurological examination

  • CBC (complete blood count)

  • Chemistry (biochemical screen)

  • Urinalysis

  • Over-the-counter urine tests for exposure to marijuana

With the exception of the last test, the goal of the above tests is typically to ascertain that no other conditions or toxicities are in play as well as to help manage potentially exposed patients’ supportive care.

Affected Breeds

All breeds of dogs and cats seem equally susceptible to the effects of marijuana toxicity. Presumably, however, some breeds of dogs and cats may be genetically predisposed to some of marijuana’s more severe effects (as is presumably the case in humans as well).


Pets who ingest marijuana may be treated by induction of vomiting. This is only recommended if the drug has been ingested within the hour.

Treatment is often unnecessary, particularly if only small amounts are ingested and the clinical signs are mild. Treatment of marijuana toxicity becomes necessary when the degree of sedation that exposed animals experience is determined to be profound enough to warrant the need for hospitalization and supportive care.

Most pets hospitalized for supportive care post-exposure receive the following as part of their supportive care regimen:

  • Intravenous fluid administration

  • Thermoregulatory support (warming)

  • Anti-nausea medication

  • Antacid medication

Veterinary Cost

The cost of toxic exposure to marijuana depends wholly on the amount of marijuana ingested. Hospitalization may cost up to $1,000 or more per day if intensive care is required. More commonly, however, pets will receive only 24 hours of care or less with invoices well below that sum.


Marijuana intoxication is 100% preventable when pet owners take simple steps to manage their recreational or medicinal marijuana usage in ways that limit their pets’ exposure.

Smoking or vaporizing marijuana in rooms where pets are not present is helpful, but given that pets are most easily exposed to toxic quantities when they’re given free access to the drug itself, being careful to keep it in pet-safe containers is a far more effective means of prevention.


Janczyk P, Donaldson CW, Gualtney S: Two hundred and thirteen cases of marijuana toxicoses in dogs. Vet Hum Toxicol 2004 Vol 46 (1) pp. 19-21.

Shell, L: Marijuana Poisoning. Veterinary Information Network, 2006.