With the increasing availability of marijuana (Cannabis sativa) in Colorado, pet exposure to marijuana has been on the rise. Dr. Meola et.al. reported in 2012 that there was a 146-fold increase in registered medical marijuana users in Colorado, and a 4-fold increase in dogs presented for marijuana toxicosis from 2005-2010 in two large Colorado Front Range veterinary emergency centers. There were two deaths out of 125 marijuana intoxicated dogs. The deaths were likely from ingestion of highly concentrated medicinal products. Pet Poison Helpline, an animal poison control center has also experienced a 200-percent increase in pet marijuana cases over the last 5 years. Significantly more dogs than cats appear to be involved.
Pet exposure occurs through secondhand smoke and direct ingestion of marijuana or foods containing marijuana. Most exposure appears to be unintentional but there is increasing interest in the use of marijuana for pain management, appetite stimulation, and prevention of vomiting in pets with cancer. Unfortunately, there currently is little research documenting the benefits of marijuana consumption, the optimal dosages, or details of how marijuana works in pets. With concerns about potential toxicity and lack of scientific documentation, a cautious approach is recommended until more research can be completed and standardized marijuana preparations become available.
More than 400 chemicals have been identified in marijuana; over 60 of these are cannabinoids including the major psychoactive compound cannabinoid δ-9-tetrahydrocannabinol (THC). Whole marijuana has not been approved by the FDA for medical use, however, cannabinoid-based drugs like Nabilone and Dronabinol (synthetic cannabinoids) are available by prescription in the United States. An extracted cannabinoid, available in Europe, is currently undergoing clinical trials in the United States. In humans, indications include pain, loss of appetite, and control of vomiting in cancer and AIDS patients.
The amount of marijuana required to cause a toxicosis in dogs or cats is dependent on the THC concentration. THC concentration is variable between plant varieties, plant part used, and growing and storage conditions. The minimum lethal dose of THC for dogs is considered to be 3g/kg of body weight. Effects of intoxication are seen 30-90 minutes after ingestion and most resolve over a period of 3-12 hours. However, effects can last up to 4 days while the body is detoxifying. Signs of intoxication can include severe depression, walking as if drunk, lethargy, and even coma. Some pets have low heart rates, low blood pressure, depressed respiration, diarrhea, and dilated pupils. Others can be hyperactive, vocalize, and even have seizures. Vomiting is often seen with dogs even though THC has anti-vomiting properties. Intoxicated pets may lack the coordination necessary to consume food and water and may be prone to dehydration and injuries related to falling.
Use of the human urine test for dogs to detect THC has been controversial. Recent studies show inconsistent ability to detect THC in dog urine resulting in false negative results. This creates a problem for diagnosis because even though serious long-term health issues and fatality from marijuana intoxication have been extremely rare, the newer, highly concentrated medical strains of marijuana and synthetic cannabinoids have more potential for serious problems. A further concern is that marijuana toxicosis appears similar to other serious poisonings like antifreeze and other drug intoxications. Toxicity in pets can also occur from chocolate and xylitol which may be ingredients in foods mixed with marijuana.
While most pets with marijuana toxicosis recover with no problems, caution is warranted. Vomiting can be induced by your veterinarian to reduce the potential for toxicity if you discover the marijuana ingestion within 30 minutes and your pet has no signs. Some authorities also recommend giving activated charcoal after marijuana ingestion in an attempt to reduce the absorption in the digestive tract. Supportive treatments include keeping the pet warm and minimizing sensory stimuli. Pets with severe agitation may require sedation. Intravenous fluids may become necessary if prolonged vomiting has occurred or if the pet is unable to drink for an extended period.
Significant optimism exists about the potential benefits of marijuana for pets. However, a great deal of research still needs to be completed, especially with the newer, high THC concentration products. Therefore, even though serious health problems have been rarely reported in pets, a cautious approach is important. Marijuana toxicosis can also mimic other more serious poisonings. Contact your veterinarian if you have questions about marijuana toxicosis in pets or if you suspect your pet has ingested marijuana.
— Ron Carsten, DVM, Ph.D., CVA was one of the first veterinarians in Colorado to use the integrative approach, has lectured widely to veterinarians, and has been a pioneer in the therapeutic use of food concentrates to manage clinical problems. In addition to his Doctor of Veterinary Medicine, he holds a Ph.D. in cell and molecular biology and is a certified veterinary acupuncturist. He practices integrative veterinary medicine in Glenwood Springs.
Pet exposure occurs through secondhand smoke and direct ingestion of marijuana or foods containing marijuana.