Marijuana in Pets

Marijuana in Pets 
Jeff Dennis, DVM, DACVIM

Marijuana is believed to be the most commonly used illicit drug in the United States. With its legalization for medical use in humans and its recent decriminalization in Colorado and Washington, the frequency with which pets are being exposed to marijuana or one of its derivatives is increasing.

The toxic chemical in marijuana is delta 9-tetrahydrocannabinol or THC. Dried leaves and flowers of the hemp plant Cannabis sativa contain 1-8% THC. Hashish, compressed resin produced from the flowering tops of the plants, contains 10% THC. Hash oil or butter, a concentrated form of hashish or marijuana in which the cannabinoids are extracted into the fat of oil or butter, can have a THC concentration exceeding 50%.

The most common means by which dogs and, uncommonly, cats are exposed to marijuana is by ingestion of home cooked or commercial products containing THC. THC is stored in the tissues of the brain, liver and kidneys. Being highly lipid soluble the chemical is also stored in fat deposits where it can remain for days. The majority of the THC is excreted via the biliary system and eliminated via the feces.

Signs of marijuana intoxication typically occur within 60 minutes of exposure and can last several days. The THC binds to cannabinoid receptors in the brain where it interacts with the neurotransmitters norepinephrine, dopamine, serotonin and gamma-aminobutyric acid inducing varying stimulatory and inhibitory signs involving the GI, cardiovascular and neurologic systems.

 Signs of marijuana intoxication

  • Ataxia
  • Bradycardia
  • Depression or dysphoria
  • Hyperstartle response
  • Mydriasis
  • Tremors
  • Urine dribbling
  • Vomiting

Is it marijuana?

The challenge in diagnosing marijuana toxicity is getting the pet owner to confirm the pet’s potential exposure. Routine blood testing and imaging typically fail to demonstrate significant abnormalities.  Furthermore, over-the-counter drug tests as well as laboratory tests for THC have not yet been proven effective in pets. Luckily the signs of THC toxicity, i.e. dysphoria, drowsiness, a hyperstartle response and especially urine dribbling are pretty recognizable.

 What’s the best treatment?

Treatment after immediate exposure to marijuana could include induction of emesis and the administration of activated charcoal. Both would be contraindicated if the clinician feels the patient’s mental state predisposes the pet to the possibility of aspiration pneumonia. Interestingly, induction of emesis may not be effective as one of the marijuana’s medical uses is to inhibit nausea and vomiting in human cancer patients. The repeat administration of activated charcoal 6-8 hours after an initial administration should be considered to reduce GI absorption of the THC as it goes through eneterohepatic circulation.

Symptomatic supportive care should be individualized to the patient and would typically include IV fluids to ensure hydration and perfusion, external heating or cooling as indicated, and anti-anxiety therapy. More severely affected patients may require cardiovascular medications, oxygen supplementation or even ventilation. Intralipid therapy should be considered in more severely affected patients and those with prolonged duration of signs. Because THC is lipid soluble, it can be leached from the body with intralipid therapy. Close monitoring of these patients is important. Luckily THC has a high safety margin. To be lethal most dogs must be exposed to greater than 3 g/kg.

Could marijuana be beneficial for treating ill pets?

In humans, marijuana and its derivatives have been shown or suggested to have many potential medical uses including

  • Stimulating appetite and reducing nausea in cancer patients
  • Treatment of glaucoma
  • Increasing lung capacity
  • Controlling epilepsy
  • Reducing cancer spread
  • Slowing the progression of Alzheimer’s disease
  • Reducing the pain of multiple sclerosis
  • Relieving arthritis discomfort
  • Treating inflammatory bowel disease

Reports of marijuana’s effectiveness for treating ill pets are very limited and at best anecdotal. Marijuana is a Schedule I narcotic. Even if you live in a state where medical marijuana is sanctioned, as a veterinarian it remains illegal for you to prescribe or recommend it to treat a patient.



If you feel you may be dealing with a pet who has a potential toxicity or desire closer 24 hours or after-hours monitoring of your patient, please don’t hesitate to give us a call. Our emergency and critical care services have loads of experience dealing with all types of toxicities.