Written by: Leslie Buckland, DVM
Marijuana is a popular recreational drug used by millions of people of various ages all over the world. The psychoactive ingredient is delta 9 - tetrahydrocanbinal, common reffered to as THC. Marijuana is usually 1% to 8% THC and hashish, made from the flowers and resin of the plant, can be 3% to 6% THC.
Usually a pet toxicity case involves a dog that has inadvertently eaten some marijuana or hashish. Dogs account for about 96% of exposures and cats about 3%. There are rare reports of pets being exposed through marijuana smoke.
Clinical signs usually show up about 30 - 90 minutes after ingestion or exposure and signs may last up to 72 hours. Various systems are affected; nervous, gastrointestinal, cardiac, and urinary. Usually symptoms can include incoordination, disorientation, listlessness or depression, tremors, hyper sensitivity to light and touch, hypothermia, slow heart rate, dilated pupils, and urinary incontinence. In rare cases there can be recumbency, stupor, and even seizures.
At Guardian Veterinary Centre we typically see patients that are quiet, uncoordinated, hyper sensitive, slightly low heart rate, slightly hypothermic, and they are often dribbling urine. Unless an extremely large quantity was consumed the result is not fatal. A potentially lethal dose for dogs is 3g/kg.
Other potential toxins causing central nervous system depression must be considered as a different diagnosis, but tactful questioning of the owners can often reveal the cause. Veterinarians are not obligated to report marijuana exposures to the police. Urine testing similar to those used in humans can be done in dogs, but most veterinary clinics do not carry those tests routinely.
Treatment involves supportive care for the most seriously affected. This would include hospitalization, IV fluids, keeping the patient warm, sedation with diazepam for seizures, atropine for a severely low heart rate, orogastric lavage (pump the stomach) under general anesthesia for comatose patients. Most patients who can still walk are treated as outpatients on oral activated charcoal every 8 hours for 24 hours. Inducing vomiting appears to only be useful within 30 minutes after known ingestion due to the potential antiemetic properties of THC.
Because THC is stored in body fat, the effects of marijuana ingestion can last for up to 72 hours. Luckily it would be very rare to be a fatal toxicity and most patients are back to themselves within 12 to 24 hours.