In my oncology practice in California, clients ask me about using CBD products on an almost daily basis. In California, veterinarians are currently allowed to discuss the use of cannabinoids with clients but it is not yet legal for us to make recommendations regarding their use. In other states, it is not yet legal for veterinarians to discuss or recommend the use of cannabinoids.
This places us in a difficult predicament. In my practice, I'd estimate that more than 70% of my patients are receiving cannabinoids. This is not due to my recommendation, but mainly due to my clients' research and the recommendations of their friends.
I am thankful to have had the recent opportunity to attend a lecture given by Dr. Dawn Boothe, DVM, Ph.D. She is a board-certified veterinary internist and clinical pharmacologist currently studying cannabinoids in dogs (amongst other things). I wanted to share some of the information that she provided so that we could all be more knowledgeable on the subject.
Okay, so what are we actually talking about?
There are three types of hemp plants: Sativa, Indica and Ruderalis. Industrial hemp is classified by the USDA as being derived from the Cannabis sativa plant and having less than 0.3% THC (the psychoactive component) on a dry matter basis. For comparison sake, marijuana is derived from the same plant but would be expected to have upwards of 10% THC on a dry weight basis. Each plant has a different function. Marijuana is used for "recreational" purposes, while industrial hemp is used for making auto parts, soap, concrete, and in creating CBD products for dogs and people.
There are roughly 500 different compounds and 100 different cannabinoids in each hemp plant. THC and CBD are just two of these compounds. THC is a psychotropic compound and (in general) produces negative side effects in dogs. CBD reduces anxiety.
THC is responsible for the "pot toxicity" that we routinely see in the ER. This commonly occurs when a dog is exposed to their owner's marijuana. Dogs are significantly more sensitive to THC than humans. Signs of too much THC in a dog include: urinating uncontrollably, static ataxia (widespread stance is taken so as not to fall over), lethargy, dilated pupils, whining, agitation, possible tremor/seizure, difficulty regulating body temperature.
Is CBD legal?
Hemp-derived CBD is legal in all states except Idaho and Nebraska, where its legality is unclear. Marijuana-derived CBD (higher THC content) is legal for human medicinal use (for at least a few specific medical conditions) in most states.
Two of the major cannabinoids, THC, and CBD, have been manipulated to create approved human medications. Marinol is a synthetic THC used to treat nausea and stimulate appetite in patients with AIDS and cancer. Cesamet is a synthetic THC-like compound used to treat nausea in chemotherapy patients; it's also used off-label as an analgesic (pain reliever). Sativex is a combination of THC and CBD and is used to treat both epilepsy and to relieve the spasticity associated with multiple sclerosis. Epidiolex was approved in 2018 to help treat pediatric drug-resistant epilepsy.
So how do Cannabinoids work?
There are cannabinoid receptors throughout the body. These receptors exist on white blood cells, nerves, in the intestine, on tumor cells, in heart muscle cells, on fat and skeletal muscle cells, in the liver, brain, kidney, lung, etc. They can function to decrease nausea, inflammation, pain, kill cells, stimulate appetite, improve digestion, modulate the immune response, maintain bone mass, etc.
The human endocannabinoid system is comprised of two types of receptors (CB1 and CB2) and impacts pain modulation, memory, appetite, inflammation, and our immune system. CB1 receptors are primarily found in the brain and central nervous system, while CB2 receptors are found on immune cells and organs such as the liver, kidneys, and lungs. Cannabinoids such as THC and CBD bind with these receptors (they fit together like a lock and key) and cause changes in the resultant organ/cell.
Dogs are thought to have more cannabinoid receptors than humans, which could be why they are more sensitive to THC than humans.
There is a paucity of literature involving dogs and cannabinoids. A recent Cornell University study showed an increase in comfort and activity in a group of arthritic dogs receiving CBD oil at 2 mg/kg twice daily.
Things to watch out for:
This is a widely non-regulated industry - similar to the supplement and nutraceutical industry. This means that what's on the label, may not actually be in the bottle. Since this is an unregulated industry, a third-party company is not regularly testing brands to ensure that if they say that a certain concentration of CBD is in a product, it's actually present. If you purchase a CBD product and you're not seeing the desired effect, try a different brand.
We also have to remember that CBD products come from a hemp plant and that plant may have been growing in a field contaminated by insecticides or herbicides - something to keep in mind until the industry is regulated.
If someone were to purchase a human product and administer it to a dog, the high THC concentration may cause signs of toxicity (remember, dogs are more sensitive to THC than people). Never administer a human CBD product to a dog. Prior to administering a cannabinoid, please read the label. Be certain that there aren't any supplements or additives that may be contraindicated with any other medications your dog is taking.
Dr. Boothe regularly tests blood samples from dogs receiving CBD products. She's found that many dogs do not have CBD levels in their bloodstream that are within therapeutic range. This means that the amount of CBD that is actually in the product that the patient is consuming is not enough to actually do anything (ie. you're wasting your money). For a short time, she will actually test your dog's blood for free to determine if his CBD levels are within therapeutic range. If they aren't, it means that the product you are giving (at the current dosage) isn't doing anything. For those that are interested in this, she requests two blood samples (2 hours post-dose and just prior to the second dose), a product sample (to determine how much CBD is actually in the product), and a completed questionnaire. You can find more information here, under Cannabinoid Monitoring.
What about drug interactions?
Cannabinoids are metabolized by the cytochrome P450 enzyme system. This means that if given with CBD products, many medications will have either increased or decreased efficacy, as well as increased or decreased side effects.
If your dog is taking CBD oil while on other medications, tell your veterinarian (1) that your dog is taking CBD and (2) that CBD is metabolized by the cytochrome p450 enzyme system, so that they are aware and can make recommendations.
Each strain of hemp plant has its own unique combination of cannabinoids. Each cannabinoid has its own unique effect on a particular organ in the body or cell in the immune system. Because of this, each brand of CBD will contain its own unique signature combination of cannabinoids, and if things are not well-regulated at the company, this might even vary from batch to batch and bottle to bottle.
Due to these factors, we can't think of all CBD as being equal, because it's not. In this vein, if someone experiences amazing results with CBD it would be a bit presumptuous to expect the same results knowing the degree of variability between products and how many factors are involved.
Consider purchasing the same brand that a trusted source has had a great experience with and purchasing an oil (instead of a treat); oral absorption has been shown to be greatest with CBD-infused oil.
What do the studies show?
There is a fairly wide body of evidence demonstrating the ability of cannabinoids to decrease growth and induce cell death in various human tumor cell lines. The vast majority of this work has been done in vitro (in a petri dish).
A few human clinical trials have recently ended, which aim to determine the safety and efficacy of cannabinoids for people with various cancers. I've heard that similar trials are being done with veterinary patients. This is a process that typically takes years.
CBD products have the potential to be helpful for our pets. There is just so much more to learn about cannabinoids in dogs, and since these products have the potential to interact with many medications and organ systems, we have to remember to think about them as a medication, not just as a supplement.
When exploring new treatment options for your dog, please involve your veterinarian. If their cannabinoid knowledge is limited, seek out a local veterinarian that specializes in holistic or integrative medicine, if possible; they're likely to have the most experience with these products.
Dr. Lori Cesario
Board Certified Veterinary Oncologist
PS: I'm happy to now offer online oncology consultations. Learn more about how this service can help by visiting the Vet Cancer Consultants site.
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