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The Dangers of Marijuana for Dogs

By Amanda Lohin, DVM


MSPCA-Angell West, Waltham




The recreational, psychogenic drug, marijuana, is formed from the leaves and tops of the hemp plant (Cannabis sativa) and has been used in many different cultures for a variety of different recreational, religious and medical purposes for over 5000 years (Krietzer, 2009). Interestingly enough, marijuana was actually one of the most commonly prescribed medications in the United States until it was made illegal in the early 1900s and then declared a Class II controlled substance (Burns, 2006). Over the last few decades, marijuana’s effectiveness in pain control and appetite stimulation has led to legalization for medical use in several states. As many may already know, the people of Massachusetts voted to legalize marijuana for recreational use in November 2016, which went into effect on December 15, 2016, making marijuana and marijuana products (i.e. edibles) more readily available to the public.

So, what does this mean for our pets? Well, marijuana ingestion/toxicity is actually one of the more common toxicities seen in dogs through the ER, perhaps aside from chocolate and raisins/grapes. The active, psychogenic ingredient in marijuana is delta 9-etrahydrocannabinol (THC), which can vary greatly in concentration depending on the product (much higher concentration in hashish and hashish oils). This should be taken into account in cases of toxicity and is important information to relay to any doctor seeing your pet who may have ingested marijuana.

Over 99% of cases following ingestion of marijuana present with neurologic signs consistent with Central Nervous System (CNS) depression, including ataxia (incoordination when walking), head bobbing, lethargy/listlessness, dilated or pinpoint pupils, slow or rapid heart rate (depending on amount of marijuana ingested) and often urinary incontinence (dribbling urine). In some, but not all cases, low blood pressure and body temperature may also be seen. Onset of signs varies based on the individual patient’s metabolism, but most commonly is within 1-3 hours of ingestion and can last anywhere from 30 minutes to 96 hours (based on the amount and type of marijuana ingested) with the average being 18-24 hours. Ingestion of hashish or marijuana butter tends to result in more severely affected animals, who can have serious enough CNS depression to result in seizures or coma and the need for temporary mechanical ventilation.

Initial treatment recommendations for any pet having ingested marijuana will vary based on timing and/or degree of clinical signs present. If less than 30 minutes have passed since known ingestion of marijuana or a marijuana product, emesis (vomiting) can be induced to physically remove the compound from the system. If more than 30 minutes have passed since known ingestion, the anti-nausea effects of the THC will likely be strong enough that it will be difficult to induce vomiting. Additionally, vomiting should not be induced in any clinically depressed dogs for risk of aspiration pneumonia. Although not always necessary, administration of activated charcoal by mouth every 8 hours for 24 hours can help to reduce the severity and duration of signs; often times, exposure is minor enough that this is not necessary (Donaldson, 2002).

For mildly affected patients, simple outpatient care with subcutaneous fluids (to encourage faster excretion of the toxin) and minimizing stimulation (i.e. provide a quiet, dark environment) at home is recommended, with most animals recovering within 12-24 hours. For more severely affected animals, hospitalization for intravenous fluid therapy, close monitoring of heart and respiratory rate, as well as sedatives for agitation are sometimes needed. Uncommonly, CNS depression can be severe enough to induce coma, necessitating temporary mechanical ventilation until the drug can be metabolized and excreted (Osweiler et al).

For more information on the MSPCA-Angell West Emergency Service, please visit or call 781-902-8400.


  1. Donaldson CW. Marijuana exposure in animals. Vet Mede 2002 Vol 97 pp. 437-439.
  2. Janczyk P, Donaldson CW, Gualtney S: Two hundred and thirteen cases of marijuana toxicoses in dogs. Vet Hum Toxicology 2004 Vol 46 (1) pp. 19-21.
  3. Kreitzer FR, Stella N. The therapeutic potential of novel cannabinoid receptors. Pharm Ther. 2009; 122: 83-96.
  4. Osweiler GD, Hovda LR, Brutlag AG, et al. Small Animal Toxicology. Wiley-Blackwell; 224-229.