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Marijuana toxicity in dogs: Part 1 | VETgirl Veterinary Continuing Education Blog

In today's VETgirl online veterinary continuing education blog, we review marijuana toxicosis in dogs. In this 2-part blog, we'll discuss all you need to know about this up-and-coming toxicosis in veterinary medicine. Today, we'll review marijuana, pharmacokinetics, and clinical signs seen with poisoning in dogs. (Cats are rarely affected or exposed).

With the legalization of marijuana is several states, there has been an increased prevalence of accidental exposure to dogs, cats, and children within the past few years.1-3 As a result, veterinarians need to be aware of this growing toxicant. Judicious history taking, along with rapid recognition of clinical signs, is imperative, as pet owners are often unwilling to admit to this illicit drug toxicosis in their pets. Thankfully, with appropriate decontamination and treatment, the prognosis is excellent with symptomatic and supportive care.

Marijuana, found in the Cannabis sativa plant, contains the toxic ingredient tetrahydrocannabinol (THC). Marijuana is also common known under the nicknames Mary Jane, pot, hemp, hashish, pot, grass, weed, devil weed/week, etc.4 Synthetic marijuana, commonly found in stores, causes similar clinical signs (see treatment). THC directly affects cannabinoid (CB1) receptors in the brain, affecting neurotransmitters [e.g. dopamine, serotonin, gamma-aminobutyric acid (GABA)].4,5 This can result in either stimulatory or inhibitory signs.

Pharmacokinetics
Marijuana is rapidly absorbed either orally or when smoked (e.g., via inhalation), and is eliminated via the liver, bile (55%), feces (45%), and urine (17%).4 Some enterohepatic recycling occurs.5 Duration of signs typically occur within 30 minutes, and can last up to 3 days (with an average duration of clinical signs of 18-24 hours).4 Important to note is that clinical signs can be seen at very low doses of marijuana exposure; that said, the LD50 in dogs is extremely high (considered to be > 3 g/kg).5

Clinical signs
Animals may exhibit mild to moderate signs after inhalational exposure (e.g., smoke), but are more likely to become symptomatic after ingestion (which is the more common route of accidental animal exposure). Clinical sign include:

  • Ataxia
  • Disorientation
  • Hyperesthesia
  • Agitation
  • Hyperactivity
  • Dysphoria
  • Mydriasis
  • Behavioral changes
  • Hypersalivation
  • Vomiting
  • Bradycardia or tachycardia
  • Hypoventilation
  • Urinary incontinence
  • Hypo0- or hyperthermia
  • Tremors
  • Seizures
  • Coma
  • Death

Signs can develop quickly (within 5 minutes) or be delayed up to 12 hours; most often, occur with 1-3 hours of exposure.4

Next week, we'll talk about specific testing (e.g., urine drug tests - should you use them) and treatment. Tune in next week for more information on our VETgirl blog!

REFERENCES
1. Wang GS, Roosevelt G, Le Lait MC, et al. Association of unintentional pediatric exposures with decriminalization of marijuana in the United States. Ann Emerg Med 2014;63(6):684-689.
2. Wang GS, Roosevelt G, Heard K. Pediatric marijuana exposures in a medical marijuana state. J Am Med Assoc Pediatr 2013;167(7):630-633.
3. Meola SD, Tearney CC, Haas SA, et al. Evaluation of trends in marijuana toxicosis in dogs living in a state with legalized medical marijuana: 125 dogs (2005-2010). J Vet Emerg Crit Care 2012;22(6):690-696.
4. Marijuana. Klatt C. In Blackwell’s Five-Minute Veterinary Consulting Clinical Companion: Small Animal Toxicology. Wiley-Blackwell, Ames. 2011:pp.224-229.
5. Fitzgerald KT, Bronstein AC, New quist KL. Marijuana poisoning. Top Companion Anim Med 2013;28(1):8-12.

2 thoughts on “Marijuana toxicity in dogs: Part 1 | VETgirl Veterinary Continuing Education Blog

  1. Hi Justine & Garret,
    I shared with Justine at the Chicagoland Vet Conf back in May that I have been studying medical cannabis for over 4 years now. I really appreciate you guys starting the dialog. I want to share some points of interest (which you probably are already aware of). 1) Many of the toxicity events involve the “edibles” that contain chocolate, raisins, macadamia nuts etc.. 2) Dogs have about 10 X the receptors in the brain than humans (for cannabinoids) and that is why doses with THC should be very low and the strain of cannabis should have an ultra low THC content. 3) CBD is currently the most widely used and “Full Spectrum” has shown to be far superior than an isolate. The CBD products are also recommended to start with a low dose. (Saying: Go low – Go slow) In Dr. Robert Silvers book he recommends 0.05mg – 0.10 mg/kg to start after a week or two 1 – 5 mg/kg once or twice a day.
    On a side not – I trust your conference went great and I am still bummed I was not able to attend! Later, Dave

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