The plant Cannabis sativa is an herbaceous flowering annual that was originally native to central and eastern Asia. It has been cultivated throughout recorded history as a source of fiber for fabric and rope, seed oil, animal feed, and medicine. Evidence exists that some ancient cultures recognized the psychoactive properties of the plant. Burned cannabis seeds have been found in the tombs of shamans in Siberia dated to about 500 BC. At about the same time, the Greek historian Herodotus recounted how the nomadic Scythians of Central Asia inhaled smoldering cannabis flowers to become intoxicated. Also, around 500 BC, ancient Hindu healers used the plant to settle stomachs and stop vomiting.
Cannabis in the United States
The history of the cultivation of cannabis in this country begins with early colonists who raised hemp for textiles, paper, sails, and rope. Both George Washington and Thomas Jefferson are reported to have farmed hemp on their plantations. In the mid-1800s, English physicians returning from India began using cannabis to treat a wide variety of conditions ranging from arthritis to migraine headaches. By the latter half of the 19th century, the first accounts of the use of marijuana as a recreational intoxicant can be found in American literature.
As of 2025, federal law in the United States still bans the use, possession, and distribution of marijuana. In 1970, the Controlled Substances Act labeled marijuana, along with other drugs such as LSD and heroin, as a Schedule I drug. This category includes drugs with both a high potential for abuse and without any recognized medical value. As of 2025, 24 states in the United States have legalized recreational marijuana use. As of March 2025, 38 additional states have approved the use of medical marijuana only. Similar legislation for reform is under consideration in several other states.
In 2000, the state of Colorado passed an amendment legalizing the sale and possession of marijuana for physician-approved medical uses. By 2010, there were 717 licensed medical marijuana dispensaries in Colorado and 106,000 registered card-carrying medical marijuana users in the state. In Denver, there are now more marijuana dispensaries than Starbucks coffee outlets. It is reasonable to assume, due to the vast revenue being generated from marijuana sales, that eventually, we can expect to see the nationwide repeal of existing marijuana laws.
Claims of Health Benefits
The use of marijuana has been proposed for a variety of medical conditions. Marijuana enthusiasts have made claims for marijuana treatment for epilepsy, depression, insomnia, PTSD, anxiety, migraines, arthritis, chronic pain, muscle spasms, Parkinson’s disease, and Tourette’s syndrome, to name a few. Marijuana is approved for medical use in many states, though qualifying conditions vary; the most common include cancer, HIV/AIDS, epilepsy, glaucoma, chronic pain, severe nausea, wasting syndrome, muscle spasms, and multiple sclerosis. The use of medical marijuana for various conditions in animals also has been proposed and is controversial.
The claims of the benefits of delta-9-tetrahydrocannabinol (THC) in the treatment of a wide variety of diseases and conditions in both humans and animals have not been supported by robust clinical evidence. Extensive clinical trials are needed to support or reject claims being made concerning the benefits of marijuana as a medication. So far, neither the government nor the drug companies have adequate incentives to encourage them to undertake or underwrite these much-needed studies. As a result, all that remains for most of the claims made is anecdotal evidence.
Marijuana Comes in Many Forms
Marijuana edibles can be found in dispensaries in a variety of forms. Cookies, brownies, candies, and a vast selection of sweets are popular and readily available. The effects of orally ingested marijuana do not appear as rapidly as signs following smoking and inhaling the drug. However, the effects of orally ingested THC persist much longer than those by inhalation.
Marijuana-containing baked products utilize medical-grade THC butter. Plants are boiled to extract the THC, which is readily absorbed by fats. Butter is then added to the mix to absorb the extracted THC. This THC-sautéed butter, now rich in THC, is used to make food products free of the plant’s crunchy stems, leaves, and flowers. If the process is repeated, the butter can have concentrate THC levels higher than those found in the plants used.
Canines Commonly Affected by Marijuana Intoxication
Dogs and cats are very susceptible to marijuana intoxication, but it is dogs that are more commonly affected. Dogs can be intoxicated by marijuana through inhalation of secondhand smoke; ingestion of seeds, stems, leaves, and flowers; ingestion of edible marijuana products; and/or the ingestion of concentrated THC or hashish oil. The marijuana plant produces psychoactive resins called cannabinoids. The highest concentration of cannabinoids is found in the female flowers of the plant. The primary psychoactive entity is THC.
Secondhand inhalation of marijuana smoke by dogs is certainly possible, but the leading cause of canine marijuana exposure is through the ingestion of edible products. At our busy emergency room, we see one or two dogs daily that have ingested some form of marijuana. It has become such a common occurrence since the law change that our receptionists can recognize the telltale signs of marijuana ingestion. Intoxication resulting from marijuana edibles is primarily a phenomenon seen in dogs. Cats lack the developed taste buds for sweets found in humans and dogs. Dogs are the victims of their taste preferences.
Although the margin of safety following marijuana ingestion has consistently been reported to be very high, the lethal dose is apparently about 3 grams per kilogram of body weight. A 2012 study published in the Journal of Veterinary Emergency and Critical Care reported the deaths of two dogs after eating foods made with THC butter. At our practice, we have seen two tiny Yorkie brothers, both weighing less than 5 pounds, succumb to the ingestion of marijuana edibles. They died as a result of respiratory arrest.
Is My Dog High?
Clinical signs in dogs usually begin within 60 minutes following ingestion. In dogs, the majority of THC is metabolized by the liver. After metabolism, 10 to 35 percent is excreted in the urine, and 60 to 90 percent is excreted in the feces. THC is stored in adipose tissue with a biological half-life of about 30 hours. In dogs, 80 percent of the THC is excreted from the body in five days. As a result, the effects of marijuana on dogs last much longer than on human beings.
The precise action of THC upon the nervous system that causes the psychoactive clinical effects of marijuana remains unknown. In humans, THC interrupts memory and cognition, disrupts motor activities, and inhibits pain, nausea, and vomiting. The effects of THC on people are believed to be caused by the alteration of the action of various neurotransmitters in the nervous system. In dogs, ingestion of large amounts of raw marijuana may cause gastrointestinal irritation, resulting in vomiting and diarrhea.
The time of onset of clinical signs depends on the dosage ingested and the route of exposure. Clinical signs of THC poisoning in dogs include incoordination and stumbling, drooling and hypersalivation, depression, disorientation, drop in body temperature, dilated pupils, and slower heart rate. More than 50 percent of affected dogs dribble urine. Dogs may also show tremors. The size of the dog, its age, and any underlying medical conditions it may have also play a role in the duration and severity of the intoxication.
Severely affected dogs may vocalize, become hyperexcitable, and show increased sensitivity to light, sound, and motion. Dogs eating large amounts of marijuana edibles may be unable to rise and appear to be in a stupor. Although most dogs recover completely and no long-term neurologic or cardiovascular effects have been observed, intoxicated dogs may take two to three days to return to normal.
Getting Back to Normal
At present, there is no specific antidote or physiological antagonist for marijuana intoxication. The objectives of treatment in dogs poisoned with the THC from marijuana include prevention of further absorption of the drug and supportive care while they are recovering. Activated charcoal is administered to block further absorption. Any acute anxiety and overstimulation are managed with valium. Dehydrated or cold, hyperthermic dogs may require intravenous fluids. Affected animals are usually hospitalized, and their temperature, pulse, and respiration are closely monitored. Animals who are not severely agitated or debilitated can be treated by vigilant observation and in a quiet, supportive, and protected environment.
Recovery is dose-dependent and may take 24 to 72 hours. Longer recoveries are not uncommon in dogs that have ingested a large amount of edibles. Although dogs exposed to higher dosages require more aggressive and longer treatment, the majority of dogs that have ingested THC recover completely with no long-term adverse effects.
Better Tests Needed
We use urine to test for illicit drugs. THC can be detected in canine urine for several days following exposure. Human drug-screening kits are not infallible, and false negatives can be obtained if the test is run too soon after ingestion of THC. Gas chromatography and mass spectrophotometry tests are more accurate than urine drug-testing kits but may take several days to a week before results are obtained.
What is needed is a more reliable, consistent, rapid, inexpensive, and reproducible cage-side test to confirm marijuana intoxication. Nevertheless, by obtaining a truthful history, doing a sound physical exam, establishing a minimum database with the proper diagnostic tests, and ruling out a list of differential diagnoses of other possible causes, we can identify THC poisoning.
The dose can predict the severity of clinical effects caused by marijuana ingestion, but the exact potency of an edible may be almost impossible to determine. This is because 5 grams of poor-quality marijuana is not necessarily stronger than 2 grams of a more THC-enriched strain.
Poor Labeling Practices
The manufacturers’ labeling procedures themselves can be misleading. Many manufacturers list product strength on the package as 5x, 10x, 20x, etc., where 5x is a typical one-person dose. Some producers say how much raw marijuana is infused by grams in the product. However, actual potency may vary tremendously, even in grams of the raw plant.
Other producers’ labels list “cannabinoids” in grams. Which cannabinoids are included, psychoactive ones or harmless, inert molecules? Marijuana is composed of dozens of cannabinoids, both active and inactive. This is misleading both to the buyer and to emergency room clinicians. Other labels list milligrams of “active” cannabinoids. Again, which ones and how much?
The marijuana growers have stated something along the line of, “Label instructions are rough guidelines and may vary from individual to individual.” This does not seem to be an acceptable explanation for a drug that can have such dramatic and potentially serious effects. As of 2025, there was no uniform system in place to determine the strength of edibles and actual dosage. In addition, there was no reliable system at work to oversee edible marijuana protection. In Colorado, all that is needed to produce and sell edibles to dispensaries is a cooking license, which requires only a one-time inspection.
With such a lax system, there is real potential for food poisoning. Spoiled ingredients, mold, bacterial toxins, spider mites, and pesticides are just a few of the problems the absence of regulation invites. Also, allergens such as nuts are not detected. The industry is in its infancy but needs to make a greater effort regarding labeling, packaging, and ingredient safety.
Studying marijuana intoxication in dogs is essential not just to protect dogs’ health but also because canine poisonings can serve as a sentinel for what could happen in children. Dogs and children are the unintended collateral damage of increasing edible marijuana use. The marijuana industry could do more to improve labeling and product safety, develop uniform standards for identification of the strength of various strains, and regulate the purity of the edibles more strictly.
This adapted excerpt is from It Started With a Turtle: One Man’s Life on a Blue & Green Planet by Kevin Fitzgerald (Archway Publishing, 2024). It is reproduced with permission from Archway Publishing. This adaptation was produced for the Observatory by Earth | Food | Life, a project of the Independent Media Institute.
