Marijuana Toxicity in Pets

Written by: Nancy M. Thompson, CVT- Boston West Veterinary Emergency & Specialty

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Marijuana has become legal in many states and is becoming very common in households for medicinal and therapeutic purposes. With this, the Pet Poison Helpline line has experienced a 448% increase in marijuana toxicity cases over the past 6 years. Here’s some information that you need to know about marijuana ingestion in pets.

What is marijuana?

Marijuana or Cannabis sativa/Cannabis indica is used for recreational and medicinal use. Tetrahydrocannabinol (TCH) and cannabidiol (CBD) are the two most commonly recognized, utilized, and studied cannabinoids (although there are over 80 different cannabinoids in marijuana plants.) The primary difference between between the two is that:

  • THC causes psychotropic effects and has a moderate level of toxicity.
  • CBD is non-psychotropic and is felt by many investigators to be non-toxic or have limited toxicity.

The exact amount of each cannabinoid varies widely from strain to strain and plant to plant.

Clinical signs of marijuana toxicity in pets

Pets can be poisoned by marijuana in many different ways, such as ingesting marijuana edibles (brownies or pot butter), ingesting their owner’s marijuana supply in any formulation, or by secondhand smoke. Some common symptoms of toxicity you may see are:

  • Sedation/lethargy
  • Dilated pupils or glassed over eyes
  • Dazed expression
  • Difficulty walking
  • Vomiting

More severe symptoms can include:

  • Low or high heart rate
  • Vocalization such a whining/crying
  • Agitation
  • Trouble regulating temperature causing body temperature to drop or rise
  • Incontinence/dribbling of urine
  • Tremors
  • Seizures
  • Potentially coma

Signs can be seen anywhere from 5 minutes to 12 hours after marijuana exposure and can last from 30 minutes to several days depending on the dose ingested and the size of the pet.


Although there is no true antidote for marijuana, veterinarians can give supportive care to help pets through the clinical sings. This may include:

  • Supportive care for regulating body temperature to ensure pets aren’t too hot or cold
  • IV/SQ fluids to help maintain hydration
  • Anti-vomiting medication to help with fluid loss
  • Monitoring the pet’s heart rate to ensure it’s stable
  • Providing a safe area so pets don’t injure themselves if they’re having trouble walking.
  • In some cases, veterinarians may give activated charcoal (a liquid pets drink that helps to bind the toxin in the stomach or intestines and prevent absorption into the body.

Pets typically do well with supportive care, however large ingestions of marijuana can be dangerous. Some common problems with diagnosing and treating marijuana toxicity is due to incomplete history due to stigma, owners being on vacation, pharmaceutical products, or legal repercussions. It’s important to reassure owners that the hospital is only interested in providing appropriate medical care for their pet. This is necessary so that their pet is getting treated appropriately and not getting anything that isn’t necessary.


To prevent marijuana toxicity in your pets you must keep marijuana edibles and products out of reach in high cabinets or a locked drawer when not in use. If marijuana is being smoked, pets should be kept in a separate area with good ventilation until the smoke has cleared.

If you feel that your pet has ingested marijuana your best course of action is to have them seen and treated.

And please remember: it’s nothing to be ashamed or embarrassed about! If you don’t tell us that there is even a possibility that your pet ingested marijuana, then their diagnosis and treatment can be delayed. We are only interested in your pet’s wellbeing! 




Metronomic Chemotherapy


Written by Mairin Miller, DVM (Residency-trained in Oncology)


Metronomic chemotherapy (MC) is the oral administration of anticancer drugs at low, minimally toxic doses on a frequent or continuous schedule. This is commonly executed using a combination of cyclophosphamide (cytoxan) and piroxicam, however several other protocols have been published, including chlorambucil, etoposide and thalidomide. It is often an attractive option for clients due to its relatively low toxicity profile, moderate cost, and less intensive recheck schedule. In contrast to more traditional chemotherapy administered at maximally tolerated doses (MTD), the anticipated outcome with metronomic chemotherapy is disease stabilization or dormancy, therefore it is often pursued as a maintenance therapy, following surgery and/or MTD chemotherapy.

Mechanisms of Action

  1. Antiangiogenic – Angiogenesis, which is the formation of new blood vessels from larger preexisting vessels, is critical for tumor development. This involves the migration, growth and differentiation of vascular endothelial cells, which line blood vessels. Tumor angiogenesis is regulated by inhibiting anti-angiogenic factors and activating pro-angiogenic factors. Metronomic cytoxan administration has been associated with a significant decrease in tumor microvessel density in dogs with soft tissue sarcomas. It also was shown to decrease anti-angiogenic factors VEGF and thrombospondin-1 in a mouse model.
  2. Immunoregulatory – In patients with cancer, immunosuppressive T regulatory (Treg) cells are recruited by the tumor and present at high levels. This suppresses the anti-cancer immune responses and induces tolerance, allowing tumors to evade the immune system. Metronomic cytoxan and chlorambucil have been shown to reduce circulating Treg numbers in dogs with soft tissue sarcomas.
  3. Inhibition of cancer stem cells and tumor dormancy – Cancer stem cells are a subpopulation of cancer cells that act like normal stem cells and can initiate tumor growth. It is theorized that metronomic chemotherapy can target cancer stem cells thereby inducing tumor dormancy, causing a prolonged period of stable disease.

Metronomic Chemotherapy - Source

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Potential Side Effects

Metronomic chemotherapy is well tolerated with minimal risk for bone marrow suppression or gastrointestinal (GI) upset. However, higher cumulative doses of Cytoxan have been associated with an increased risk of developing sterile hemorrhagic cystitis (SHC), which has been reported in 3.6 – 32% of dogs receiving metronomic cytoxan. Acrolein, a breakdown product of cyclophosphamide, is known to irritate the bladder epithelium. Symptoms of SHC include pollakiuria, stranguria and hematuria. In a 2017 study the addition of daily furosemide at 0.5 – 1 mg/kg/day significantly decreased the incidence of SHC with metronomic cytoxan.

Metronomic chemotherapy is often administered in conjunction with an NSAID, such as piroxicam, therefore we can see toxicity associated with these medications. Piroxicam alone has been reported to cause GI toxicity in 6-23% and nephrotoxicity in approximately 5% of cancer-bearing dogs.


The management of multiple different cancers using metronomic chemotherapy has been reported in the literature. One of the most common applications is in preventing local recurrence in dogs with incompletely excised soft tissue sarcomas. Another protocol using cytoxan, etoposide and piroxicam showed similar survival times to doxorubicin alone when treating dogs with hemangiosarcoma post splenectomy, with a median survival time of 178 days. Metronomic chlorambucil has be trialed in dogs with transitional cell carcinoma of the bladder in dogs, with 70% having a response or sustained stable disease for median of 119 days. Recently, a combination of cytoxan, piroxicam and thalidomide was shown to significantly prolong survival times in dogs with advanced primary lung tumors. Lastly reports of a response in dogs with a mast cell tumor, thyroid carcinoma and histiocytic sarcoma have been published.