Marijuana - A Common Toxicity

October 29, 2019

We are presented with a large number of emergencies every year. One of the most common emergencies is the ingestion of toxic substances. Sometimes, the pet owner is aware that the ingestion has occurred and we can spring into action and start the appropriate diagnostic tests and treatment. It becomes more difficult when your pet is exhibiting clinical signs like vomiting, diarrhea, or strange behavior and it is unknown what the pet may have been exposed to. Anything you can tell is of vital importance.

Our focus this month is about one of the most common toxicities we see in dogs. Can anyone guess what it is? If you guessed marijuana, you are correct!  We see 1 to 4 cases per month. Dogs are scavengers and are more likely to ingest toxic doses than cats.  The LD50  for dogs is 3g/kg . Marijuana poisoning can occur easily and most commonly by ingestion of the dried plant or food laced in it and even inhalation.   Luckily there is a wide margin of safety, which means that a lethal dose is very high and so it is extremely rare for pets to ingest enough to cause death, but treatment and supportive care is often necessary, especially in our smaller patients.

Signs typically begin 30-60 minutes after ingestion and because it is stored in the body’s fat deposits it can last 18-36 hours.  The symptoms are often quite classic but can sometimes be very similar to other toxicities.  These signs are glassy eyes, stumbling/incoordination, dilated pupils, vomiting, chills, agitation and excitement, urine dribbling and sometimes seizures. Histories can be misleading or incomplete and can be problematic to obtain accurately because of the legal status of the drug. Our first priority is always to ensure the pet is stabilized and treated properly.

Case Study:  Brindie was a 4-year-old healthy female spayed border terrier who presented to our clinic when her owner came home from being at work all day to find her unable to stand on her own and there was vomit and urine in the kitchen. The owner immediately brought her to our clinic where she was examined by one of our veterinarians.  Brindie was found to have dilated pupils, a slow heart rate and startle reaction where she appeared to be drowsy and began to fall over but would catch herself. Her temperature was below normal. She also urinated involuntarily in the exam room.  Due to these symptoms, the veterinarian began to suspect marijuana toxicity. The owner was asked about exposure to toxins during the day as she was reportedly completely normal that morning and had been inside all day except for a bathroom break when her daughter and her friends were home. We asked specifically about marijuana and it seemed quite clear that there was no marijuana in the house. So we began to do some diagnostics to try to figure out what Brindie may have gotten into. On our list of differentials was ethylene glycol or antifreeze toxicity, xylitol (sugar supplement found in a wide variety of foods) or mushroom toxicity to name a few. We ran some blood tests and found that Brindie’s white blood cells, red blood cells, platelets and liver, kidney function and blood sugars were all normal.  At this point we became even more suspicious of marijuana toxicity and asked about possible exposure again. We recommended that we give Brindie charcoal and start her on IV fluids and keep her overnight for monitoring.  Activated charcoal is a liquid substance given orally and as it passes from through the gastrointestinal system, toxins are trapped in the charcoal so that the toxin passes through the gut without causing further harm.  Brindie was maintained on IV fluids overnight and kept warm. In the morning, Brindie was back to her normal self and we called the owner to let her know she was ready to go home!  Upon further investigation, the owner reported that her daughter and her friends had made chocolate brownies laced with marijuana. Brindie was exposed to both chocolate and marijuana!!!

Usually if your pet were to ingest marijuana, the toxicity is very mild as seen in the case presented. However, it has come to our attention that people are now putting the marijuana into a butter. THC, the active ingredient in marijuana is fat soluble. The fat in the butter is able to leech out and concentrate the TCH from the leaves and guess who loves butter? The only dog fatalities that are thought to be related to marijuana come from dogs ingesting the highly concentrated THC in pot butter.

As always, keep your pets safe and keep toxic substances out of reach, so we can all enjoy a beautiful west coast autumn.

LD stands for "Lethal Dose". LD 50 is the amount of a material, given all at once, which causes the death of 50% (one half) of a group of test animals.

Written by Dr. Robin Rainford

Come, Sit, Stay, Heal @ RainTree Veterinary Hospital