CBD for Dogs with Cancer

Cannabidiol (CBD) can be a great addition to your pet’s home care routine, especially in a hospice case. It can help reduce side effects of chemotherapeutics and reduce inflammation.

Key Takeaways

  • CBD can help with cancer side effects.
  • Dogs with cancer should not take CBD oil with prednisone.
  • You can give your dog CBD for pain relief from cancer, but run it by your vet first to make sure that it won’t interact with your dog’s other medications.

What is CBD?

Discussing CBD and cannabis can get confusing quickly, so let’s start with a few basic definitions.

  • Cannabis is a plant.
  • Cannabis has many chemical compounds, but the two most famous are cannabidiol (CBD) and tetrahydrocannabinol (THC).
  • CBD does not have psychoactive effects,1 THC does.
  • Cannabis is referred to as marijuana if it contains more than 0.3% THC.
  • Cannabis is referred to as hemp if it contains 0.3% THC or less.8

Cannabidiol (CBD) is the second most active component of the cannabis plant. It is derived directly from the hemp plant or manufactured in a lab. CBD is safe for dogs, but THC, the main natural compound in cannabis, is toxic for pets in high amounts.2

The United States Drug Enforcement Administration (DEA) lists marijuana and its cannabinoids as Schedule 1 controlled substances.3 In humans, medical marijuana contains THC, which is toxic to dogs. It is safest to choose CBD with less than 0.3% THC for pets.

While THC will likely not kill your pet, it can induce negative side effects. Ongoing research needs to be done to find a therapeutic dose for THC to be established as safe and helpful for dogs.5

Studies evaluating cannabis in veterinary medicine are ongoing. There are a variety of formulations and brands available for dogs including flavored chews, capsules, dog treats, honey, and oil products. CBD oil can be added to food, or there are topical ointments to be rubbed on the skin or ears.

Cannabis – One Species or More?

You might see the names “sativa” and “indica” thrown around with cannabis products. Some people consider these to be two different strains of the single species cannabis, while others consider them to be separate species (as in Cannabis sativa and Cannabis indica). More separate species have also been suggested.

Even botanical taxonomists don’t all agree about whether cannabis is one single species with many different strains or a genus with multiple species and strains within those.4

But no matter how you slice it, what matters most when choosing a product is the THC content.

How CBD for Dogs with Cancer Helps

Little is known about how CBD affects dogs; however, research is ongoing.6 Dogs have an endocannabinoid system just like people. This is a series of receptors throughout the body that modulates pain, inflammation, anxiety, and nausea.7 Therapeutics that interact with this system can help manage different types of pain and provide relief, and CBD acts on these receptors.7

It has been shown that dogs have a higher concentration of CB1 cannabinoid receptors (the receptors which are activated by cannabinoids) in their brains than humans.2

CBD in dogs has been suggested to:2

  • ease pain 
  • reduce inflammation
  • relieve anxiety
  • resolve nausea
  • improve appetite
  • reduce seizures

All of these are side effects that dogs can experience due to their cancer or cancer treatments.

CBD is also showing promise for helping to treat cancer directly. CBD can slow the growth of and cause death to certain types of cancer cells grown in the lab.3

One study showed that cell cultures from different types of canine cancers that were exposed to CBD oil showed a significant decrease in reproduction of the cancer cells.6,9 The cancer types involved in this study were osteosarcoma, lymphoma, and mammary carcinoma.6

The study also showed that CBD combined with vincristine, a commonly used chemotherapeutic in veterinary medicine, had synergistic effects.9 However, the potential interactions with traditional chemotherapies need further evaluation.

Another study found that CBD caused apoptosis (cell death) and mitochondrial function impairment in canine gliomas, a primary brain tumor.10

Common Uses of CBD for Dogs

CBD is thought to have several properties, including:3,7

  • anti-inflammatory
  • modulating the immune system
  • reduce pain
  • anti-seizure
  • anti-nausea

CBD could be used to help dogs experiencing any of these symptoms.

In animals and humans, CBD has been shown to be helpful with anxiety, insomnia, and chronic pain.1

In dogs, CBD has been shown to:

  • improve comfort and activity with osteoarthritis7
  • reduce seizures in epileptic dogs2

For canine cancer, CBD is typically used as part of palliative care or a hospice program rather than for anti-cancer ability in itself.5 That said, it can also be used as part of an integrative treatment plan.

Safety and Side Effects

Side effects of CBD in dogs include:2

  • vomiting
  • diarrhea
  • elevated liver enzymes
  • ataxia
  • drowsiness

This is a relatively new treatment option, and there is still a great deal that we don’t know about drug interactions, ideal dosage, and side effects.

Always discuss CBD with your veterinarian before giving it to your dog so that you can make sure it doesn’t interfere with any other medications or supplements that your dog may be taking. CBD can make some medications more effective, and can increase the side effects of others.

Giving CBD with Other Treatments

CBD is believed to be safe to give along with chemotherapy because laboratory studies on canine cancer cells have shown a synergistic effect between CBD and several chemo drugs.2 CBD can also be beneficial for relieving side effects from chemotherapy.2

There is still a lot that we don’t know about how CBD interacts with other treatments, as very few clinical studies have been done looking at real dogs with cancer.

There are no known interactions with other supplements, but all supplement usage should be discussed with a veterinarian.

When to Not Use CBD for Dogs

Use with caution in dogs with a history of elevated liver enzymes or liver disease. We don’t yet know why ALK phosphate levels are increased with CBD use, but other liver values aren’t changed. Until we know more about how this may or may not be affecting the liver, it’s best to use with caution. Your veterinarian will want to monitor your dog’s liver values, for example.11

CBD should also not be given to dogs receiving immunotherapy, as the CBD may interfere with its effectiveness.2

In humans, CBD has been found to interact with a variety of drugs. CBD should be used with caution if your dog is taking:12

  • steroids such as prednisone
  • tramadol
  • amitriptyline

There are likely other potential drug interactions, so always discuss adding CBD with your vet to ensure it won’t interfere with other medications your dog is taking.

When choosing a product, look for ones intended for use in dogs. Products intended for humans can include ingredients that are toxic for dogs, such as chocolate or xylitol.

Which CBD and Cannabis Products Should I Consider?

This is a tough question to answer directly. The regulatory environment is in the U.S. means that some veterinarians can discuss and even prescribe CBD and cannabis, and others would lose their license just for saying the letters “CBD.”

Because of federal ban on cannabis and few studies that help us understand all of these compounds, many veterinarians are in the dark unless they have specifically sought this information and used it in their practices.

There is also quality control or standardization across brands. A veterinarian might be familiar with one product, but not be able to make a confident recommendation about another product from another company, even if their labels look the same.

Our best advice is to find a veterinarian who uses cannabis and get their input on your dog’s specific case, what brand and product to use, and how to administer the product.

If you can’t do that, choose a trusted brand and rely on the company’s recommendations. They will know their products best.

It’s strange, but true that we must rely on this “apothecary” approach for now in the U.S. This will continue until the federal regulations are changed and veterinarians can freely use and understand these supplements, just like they can any other supplement.

How to Give CBD to Dogs

A dose that has been used in studies is 2mg/kg of CBD per dog’s body weight twice a day. Another option is to start by giving 0.3mg/kg of CBD twice a day and gradually increase until you find the dose that your dog responds to. This might allow you to give less CBD while still helping your dog.2

If giving a product that contains THC, start with a very low dose and give it for 14 days. If you see an improvement, gradually increase over time up to the desired dose of CBD. This “low and slow” method decreases the risk of side effects or toxicity from THC.2

It is never acceptable for your dog to show signs of a THC toxicity or “high” – if this happens, decrease future doses and consider a different product. Your dog may also need supportive veterinary care.

CBD is given as a supplement by mouth twice daily.

Refer to the dosing information on your particular product and consult with your veterinarian or a holistic vet to determine the ideal dosage schedule for your dog.

What If I Miss a Dose?

Give the next dose when you remember. If it is close to the next dosing schedule, skip the missed one and continue the normal schedule.

Do not give a double dose, as this can increase the risk of side effects.

Storage and Handling

Typically, CBD products are stored at room temperature out of reach of children and pets. Follow specific manufacturing instructions for your chosen product.

Our Take on CBD for Dogs

There is currently a lack of direct evidence for the use of CBD with canine cancer, but it seems to have many benefits that would be helpful for dogs with cancer. CBD products may be a good component of a cancer treatment plan.

They get the green light as a palliative or hospice care option for pets suffering from end-stage cancer or other end-stage diseases. It is worth asking your veterinarian about CBD supplements if your dog is in pain or has another condition that is affecting quality of life.

  1. Grinspoon P. Cannabidiol (CBD): What we know and what we don’t. Harvard Health Publishing. https://www.health.harvard.edu/blog/cannabidiol-cbd-what-we-know-and-what-we-dont-2018082414476. Published September 24, 2021. Accessed February 9, 2023.
  2. Hazzah T, Andre C, Richter G, McGrath S. Cannabis in veterinary medicine: A critical review. American Holistic Veterinary Medical Association. https://www.ahvma.org/wp-content/uploads/Cannabis-in-Veterinary-Medicine-A-Critical-Review-Vol-61_LR-3-2.pdf. Published 2020. Accessed April 29, 2023.
  3. Marijuana and cancer. American Cancer Society. https://www.cancer.org/treatment/treatments-and-side-effects/treatment-types/complementary-and-integrative-medicine/marijuana-and-cancer.html#:~:text=More%20recently%2C%20scientists%20reported%20that,of%20some%20forms%20of%20cancer. Published July 3, 2022. Accessed February 9, 2023.
  4. Piomelli D, Russo EB. The cannabis sativa versus cannabis indica debate: An interview with Ethan Russo, MD. Cannabis and Cannabinoid Research. 2016;1(1):44-46. doi:10.1089/can.2015.29003.ebr
  5. Hazzah T, Richter G. Cannabis products in small animal medicine. Today’s Veterinary Practice. https://todaysveterinarypractice.com/integrative-medicine/cannabis-products-in-small-animal-medicine/. Published August 29, 2022. Accessed February 9, 2023.
  6. Albright SM. Promising research on the use of CBD to treat canine cancer. AKC Canine Health Foundation. https://www.akcchf.org/educational-resources/library/articles/promising-research-on-the-use.html. Published March 22, 2021. Accessed February 9, 2023.
  7. Gamble L-J, Boesch JM, Frye CW, et al. Pharmacokinetics, safety, and clinical efficacy of cannabidiol treatment in osteoarthritic dogs. Frontiers in Veterinary Science. 2018;5. doi:10.3389/fvets.2018.00165
  8. Agriculture Improvement Act of 2018. Congress.gov. https://www.congress.gov/115/bills/hr2/BILLS-115hr2enr.pdf. Published December 20, 2018. Accessed April 29, 2023.
  9. Henry JG, Shoemaker G, Prieto JM, Hannon MB, Wakshlag JJ. The effect of cannabidiol on canine neoplastic cell proliferation and mitogen‐activated protein kinase activation during autophagy and apoptosis. Veterinary and Comparative Oncology. 2021.
  10. Gross C, Ramirez DA, McGrath S, Gustafson DL. Cannabidiol induces apoptosis and perturbs mitochondrial function in human and canine glioma cells. Frontiers in Pharmacology. 2021;12. doi:10.3389/fphar.2021.725136
  11. Judd B. CBD use in dogs: An update. Veterinary Partner. https://veterinarypartner.vin.com/default.aspx?pid=19239&id=10809483. Published March 11, 2022. Accessed February 9, 2023.
  12. Wilson-Morkeh H, Al-Abdulla A, Sien L, Mohamed H, Youngstein T. Important drug interactions exist between cannabidiol oil and commonly prescribed drugs in rheumatology practice. Rheumatology. 2019;59(1):249-251. doi:10.1093/rheumatology/kez304


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