According to anecdotes, cannabidiol (CBD) oil for dogs and other pets is on the rise in popularity across the U.S. Pet owners' stories and positive testimony to the cannabinoid's efficacy could very well have merit.
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Can CBD Oil Treat Dog Seizures? The Anecdotes
Dr. Andrew Rollo, a U.S. veterinarian, writes in his blog about experiences with CBD in his practice:
"My own anecdotal evidence started rolling in a few years ago when I diagnosed lymphoma in a technician’s dog. She elected to treat her dog with prednisone, adding CBD oils on her own, and the dog had a good quality of life for another eight months—more than double the life expectancy on prednisone alone."
He suggests that this and other anecdotal evidence points to CBD as potential veterinary medicine in the areas of pain relief and seizure control. Also, as underscored by his experience, there’s "certainly a need to take a long look at potential oncological benefits as well."
Rollo furthermore mentions that clients increasingly asked for CBD oil to treat canine seizures, because traditional medicines just didn't help that much. He eventually even asked himself whether he was under-servicing his clients. 
Rollo's question doesn't have an easy answer. Is it advisable to feed Fido something that's popular among pet owners but is still largely untested by research? Also, if you choose to see for yourself whether CBD treats dog seizures, what CBD dosage should you look at?
CBD Oil for Dogs—The Research into Canine Epilepsy
Cannabis is, by now, relatively well known for its numerous health benefits. While CBD—one of the healthful, non-hallucinogenic compounds found in cannabis—has been tested and proven efficacious for intractable epilepsy in humans, so far not much well-designed research has been done in canines.
Yet this might be about to change. One major clinical trial investigating the use of CBD for intractable epilepsy in dogs was launched in 2017 and is still ongoing. 
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Funded by the Canine Health Foundation (CHF), the randomized, double-blinded, placebo-controlled, crossover clinical trial study is being conducted at the Colorado State University. It forms part of the CHF's Epilepsy Research Initiative, also launched in 2017.
Dr. Stephanie McGrath, a veterinary neurologist at Colorado State University, leads the investigation and she explains the study design in an interview with the American Kennel Club:
"The study is testing CBD on dogs with epilepsy in a controlled research setting. The dogs enrolled in the study are randomly assigned to receive either a placebo or the CBD oil for 12 weeks and then, after a 4-week washout period, receive the opposite drug for an additional 12 weeks. The researchers and the owners are blinded as to which drug is given in each half of the study." 
Apparently, the dogs are examined every four weeks. The owners are also asked to fill in a questionnaire, and blood work gets done on the animals.
Yet a number of important things about CBD oil for dogs and other pets is still unknown.
Choosing CBD Oil to Treat Dog Seizures—The Main Objections Against This
An article published in the journal Toxicology Communications points out the following gaps in our knowledge:
- CBD oil to treat dog seizures and other companion animal conditions is still vastly under-researched, as already pointed out. Reports of its use are uncontrolled and largely based on public observation, which does not make for reliable data.
- Till recently, well-designed clinical study and veterinary opinion were also hampered by CBD's illegal status. This has now changed in the U.S., but there's arguably still a significant negative bias against its use, mainly due to ignorance. CBD is not marijuana, even though it is derived from cannabis. Yet a change of general perception will take time.
- CBD's short-term and long-term efficacy and safety in pets remains unknown.
- Pharmacokinetic parameters and pharmacodynamics for long- and short-term treatment still need to be investigated. (Pharmacokinetics deals with the way the drugs move through the body. This is important, because dogs metabolize CBD differently from humans. Pharmacodynamics look at the effects of drugs and their mechanism of action in the body.)
- Orally administered CBD has low bioavailability in canines—only between 13% to 19%. Intravenous application is far more effective but is not practical.
- Very little is known about the various CBD receptors in dogs' endocannabinoid systems.
- The CBD molecule is tiny and lipophilic, meaning it can build up, especially in the body's fatty tissue. It's unknown whether this poses a risk, because there's not any research on CBD's toxicology. This is true of especially long-term treatment in companion animals.
- Because of the way CBD is metabolized in the liver, drug-drug interactions could potentially be problematic. Yet again, the available CBD interaction data is preliminary and is only human-based.
Yet the article also mentions an observational study on CBD pet product perceptions, including perceived efficacy and product safety, among pet owners. The authors state: 
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How Much CBD Oil for Dogs Can Safely Be Administered?
If you choose to see whether CBD works for your dog, the risk will be on your shoulders for the aforementioned reasons. Yet some vets are already making recommendations for clients wanting to go this route.
Says Michael Petty, DVM, CVPP, CVMA, CCRT, CAAPM, in a blog post: 
"Current recommendations for oral dosing of CBD in dogs and cats are 0.02 mg/kg to 0.1 mg/kg given twice daily. According to James Gaynor, DVM, DACVA, DACVPM, of Peak Performance Veterinary Group, for pain management most dogs do well at 0.05 mg/kg twice daily, while cats do well at 0.025 mg/kg twice daily."
You would also be well-advised to choose a full-spectrum CBD oil over a pure one.
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So, in conclusion, CBD oil for dogs and other pets should not be discarded completely as a treatment option. As another veterinarian said to NBCNews BETTER: "I don't want to be the naysayer because I think there's potential here for real possible benefits. It may be a wonderful product in the future if it's regulated and we have data." Dr. Jerry Klein is the Chief Veterinary Officer for American Kennel Club. Yet at this point, it would still be prudent to inform your vet if you're considering adding CBD oil to your canine's treatment or nutritional regimen.