Marijuana – Mary Jane, pot, weed, grass, Cannabis. Whatever you call it, marijuana is controversial. At the recent Southwest Veterinary Symposium that I attended, the session on medical marijuana was one of the most-talked about sessions. So, I promised you that we would come back and re-visit this.
Cannabis is a plant from which we get hemp and marijuana. The difference is how the plant is bred. The strains that are bred for fiber, edible seeds, and oil are what we know as hemp, but the strains that are cultivated to increase their psychoactive substances are known as marijuana or cannabis.
You know that I am a total useless fact nerd, and as I was doing my research for this blog, I came across a timeline that I thought was fascinating. I won’t bore you with all of it, but I will point out some of the highlights.
2900 BC – The first mention of cannabis as a medicine is found in China. In 1500 BC, uses of cannabis in the Chinese Pharmacopeia included glaucoma, leprosy, earaches, edema, and inflammation.
1700s – The Jamestown settlers brought hemp with them to North America, and in 1762, Virginia imposed penalties on settlers who did not produce hemp on their land.
1850 – Cannabis is added to the United States Pharmacopeia as a treatment for neuralgia, tetanus, typhus, cholera, rabies, dysentery, alcoholism, opiate addiction, anthrax, leprosy, incontinence, gout, insanity, menstrual bleeding, appetite stimulation, and basically anything else that ailed you.
1906 – The Food and Drugs Act is signed by President Theodore Roosevelt, establishing regulations for product labeling. One of the requirements is the quantity of cannabis in the product.
1911-1929 – Fifteen states pass anti-marijuana laws.
1930s – Parke-Davis and Eli Lily (two huge pharmaceutical companies) are selling standardized extracts of cannabis for analgesia, sedation, and an anticonvulsant.
1930 – Harry Anslinger is appointed the first commissioner of the Federal Bureau of Narcotics, and he believes that cannabis causes insanity and increased criminal activity.
1933 – William Randolph Hearst joins the anti-cannabis movement, replacing the terms “cannabis” and “hemp” in his newspapers with “marijuana.”
1937 – The Marihuana Tax Act is passed, imposing registration and reporting requirements on growers, sellers, and buyers of cannabis. By 1938, cannabis and hemp are illegal in all states.
1964 – Dr. Raphael Mechoulam identifies delta-9-tetrahydrocannabinol (THC) as the primary psychoactive component of cannabis. He is also the first to synthesize THC.
1970 – Congress passes the Controlled Substances Act, which establishes the scheduling structure for controlled drugs. Cannabis is placed in Schedule 1 (drugs with a high potential for abuse with no currently accepted medical use and lack of safety data).
1980s – Marinol® is the first synthetic cannabinoid, and it is approved for the treatment of nausea.
1990 – Researchers at the National Institutes of Mental Health discover the cannabinoid receptor system in the human brain.
1992 – Dr. Mechoulam identifies the first endogenous cannabinoid.
1996 – California becomes the first state to legalize the use of cannabis in the treatment of AIDS, cancer, muscular spasticity, and migraines.
2000s – Research in the endocannabinoid system continues, and the DEA is considering rescheduling cannabis to a less-restrictive schedule.
What is this endocannabinoid system (ECS)? It is actually the largest receptor system in the mammalian body. There are two types of receptors in this system. The CB1 receptors are located in the brain and nervous system where they play a role in cognition, appetite, motor activity, emotions, and memory. There are also CB1 receptors in peripheral tissues like the ovaries, testes, prostate, and salivary gland. The CB2 receptors are found primarily in the immune cells in the body. To summarize, the major functions of the ECS are to relax, eat, sleep, forget, and protect.
The two major cannabinoids of interest are THC and cannabidiol (CBD). As I mentioned earlier, THC is psychoactive, and this leads to recreational use of marijuana. Medicinally, THC has been used for treatment of glaucoma, insomnia, PTSD, and anxiety disorders. The other cannabinoid, CBD, is non-psychoactive. CBD has been found to help with pain control and seizures, and CBD has anti-inflammatory, analgesic, and anti-carcinogenic effects. CBD modulates the psychoactive effects of THC as well.
Current areas of interest in cannabinoid use in human medicine include pain management, seizure control, neuroprotection (anti-oxidant effects to treat Alzheimer’s), anti-nausea/appetite stimulation, anti-cancer effects, diabetes mellitus (CBD inhibits development of diabetes in mice), bone formation/fracture healing, and treatment of MRSA infections.
With legalization of medical marijuana in many states, the interest is using cannabis in veterinary patients has increased as well. Unfortunately, there is a lack of research in veterinary species. Dogs reportedly have higher numbers of cannabinoid receptors in their brain when compared to humans, which makes them more susceptible to the toxic effects of cannabinoids. There are also reportedly differences in the CB2 receptors in dogs versus humans, and dogs metabolize cannabinoids differently than humans.
Increased numbers of pet intoxications have been reported with the increase in use and acceptance of cannabis, and the Pet Poison Helpline has actually had a 330% increase in calls about cannabis intoxication over the past 5 years. Signs of cannabis intoxication include ataxia, lethargy, dilated pupils, slow heart rate, and urinary incontinence. These signs can be seen within 30 to 90 minutes of ingestion of the cannabis, and because THC is stored in fat deposits in the body, the effects of marijuana ingestion can last for several days.
If marijuana ingestion is detected within 30 minutes, vomiting can be induced, but once the symptoms develop, the anti-nausea effects of cannabis make it difficult to induce vomiting. In addition, vomiting can be dangerous, leading to aspiration, if the pet is extremely sedated. Activated charcoal can be given if treatment is initiated within 4 – 6 hours of ingestion. After that, treatment then becomes largely supportive – fluid therapy and blood pressure support.
At the end of the day, medical marijuana appears to have benefits in treating many diseases, and it is legal in certain states for physicians. However, it is not legal for a veterinarian to prescribe marijuana. Period. Dogs appear to be more sensitive to the toxic effects of THC, and treating accidental intoxications can be expensive. Obviously, more research is needed in evaluation the potential for medical marijuana in veterinary medicine, but please don’t try to turn your pet into a guinea pig and self-medicate them. Keep watching and waiting because it looks like cannabis will eventually work its way into the veterinary formulary, too.