Canis ISSN: 2398-2942

Cannabis poisoning

Synonym(s): Cannabis sativa, marijuana, hashish, grass, pot, Indian hemp plant, dope, hash, puff, weed, ganja

Contributor(s): Catherine Morganti, Larry Thompson, Nicola Bates


  • From plant Cannabis sativa - usually found in the form of cannabis/marijuana (dried leaves and flowers of plant) or hashish (dried resin from flower tips).
  • Cause: accidental ingestion (or inhalation) of cannabis containing tetrahydrocannabinol (THC), which is the principal active ingredient.
  • Signs: acute onset is usually within 1-3 hours: ataxia, drowsiness, stupor, behavioral changes, bradycardia, hypotension, hypothermia, increased appetite, conjunctival injection.
  • Treatment: emesis (within 1 h of ingestion, only if asymptomatic), absorbents (activated charcoal), supportive therapy (intravenous fluids, warming).
  • Prognosis: good, recovery usually within 24-96 h.
Print off the owner factsheet Cannabis in pets - what are the risks? to give to your client.



  • The minimum lethal oral dose is > 3 g/kg THC for dogs.
  • Intentional intoxication of small animals using second hand smoke has been reported.
  • Fatal cases from ingestion of cannabis are rare in dogs; survival is reported after ingested 26.8 g marijuana/kg bodyweight.   
  • Deaths have been reported in dogs that ingested baked chocolate goods made with marijuana butter. 
  • Cannabidiol (CBD) hemp oil is different and made from Cannabis sativa plants which contains high concentrations of CBD and low (trace) concentrations of tetrahydrocannabinol (THC).


  • The principal active ingredient of cannabis is tetrahydrocannabinol (THC) which causes central nervous system depression and (humans report) hallucinogenic effects - the actual mechanism of action is unknown but may involve changing concentrations of biogenic amines in the central nervous system.
  • THC content of the Cannabis sativa plant can range from 1-6%. In general the THC concentration is highest in the flowering tops of the plant and the resin (hashish) that is obtained from these, and lower in the leaves and flowers of the plant.
  • THC is rapidly absorbed from the gastrointestinal tract and via the lungs but is readily detoxified by the liver.
  • Onset of clinical signs is usually within 1-3 h with recovery occuring 24-96 h later.
  • Although oral doses of THC as high as 3 g/kg are not lethal they will tend to produce severe and prolonged clinical signs
  • THC is readily detoxified by the liver so that only 6-20% of an oral dose reaches the systemic circulation.
  • The most consistently reported clinical sign in dogs is central nervous system depression.


  • Clinical signs of poisoning usually appear 1-3 hours following ingestion or a few minutes if inhaled.
    Inducing emesis within 1 h of ingestion, before the animal shows signs of toxicosis, is recommended.
  • Recovery is usually within 24-96 h depending on the dose of THC absorbed and the efficiency of detoxification and supportive therapy.


  • In the US cases of marijuana toxicosis have increased following legalisation. 


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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Fitzgerald K T, Bronstein A C, Newquist K L (2013) Marijuana poisoning. Top Companion Anim Med 28 (1), 8-12 PubMed.
  • Meola S D, Tearney C C, Haas S A, Hackett T B, Mazzaferro E M (2012) 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 22 (6), 690-696 PubMed.
  • Janczyk P, Donaldson C W, Gwaltney S (2004) Two hundred and thirteen cases of marijuana toxicoses in dogs. Vet Hum Toxicol 46 (1), 19-21 PubMed.
  • McKnight K (2003) Marijuana toxicosis. Veterinary Technician 24 (4), 264-266 ASPCA Pro.
  • Donaldson C W (2002) Marijuana exposure in animals. Vet Med 97 (6), 437-439 VetMedResource.
  • Godwin R L (1992) Unusual poisoning in a dog. Vet Rec 130 (15), 335-336 PubMed.
  • Valentine J (1992) Unusual poisoning in the dog. Vet Rec 130 (14), 307 PubMed.
  • Dumonceaux G A & Beasley V R (1990) Emergency treatments for police dogs used for illicit drug detection. JAVMA 197, 185-187 PubMed.
  • Welshman M D (1986) Doped dobermann. Vet Rec 119 (20), 512 PubMed.
  • Henney S N & Coleman M J (1984) Canine cannabis intoxication. Vet Rec 114 (17), 436 PubMed.
  • Frost C (1983) Marijuana toxaemia. Vet Rec 112 (18), 441 PubMed.
  • Godbold J C, Hawkins B J & Woodward M G (1979) Acute oral marijuana poisoning in the dog. JAVMA 175, 1101-1102 PubMed.
  • Jones D L (1978) A case of cannabis ingestion. N Z Vet J 26 (5), 135-136 PubMed.

Other sources of information

  • Hovda L R, Brutlag A G, Poppenga R H, Petersen K L (2016) Marijuana. In: Blackwell's Five-Minute Veterinary Consult Clinical Companion: Small Animal Toxicology, 2nd edition. Ames, Iowa, John Wiley and Sons Inc. pp 264-270.