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Krista Mangulsone

Both the promises and perils of CBD point to the need for science-based education, regulation and research. Many of us living in Colorado, one of the first states to legalize the sale of marijuana for both medical and recreational purposes, find ourselves touched deeply on a daily basis by stories that both uplift as well as cause grave concern for our veterinary patients.

On the up side, marijuana appears to afford a “lifesaving” alternative for a daunting gamut of difficult-to-treat disorders, including intractable epilepsy (seizure disorders that drugs cannot control). For companion animals, even the American Veterinary Medical Association website carries testimonials favoring veterinary cannabis, in which caregivers attest to significant benefits in their animals, who were unresponsive or intolerant of mainstream pharmaceuticals.

Now that marijuana is becoming legal to buy for humans in a growing number of states, many are trying it on animals. But should you be administering it to your pet? Should your veterinarian?


Because of the higher toxicity of tetrahydrocannabinol (THC) in dogs compared to humans, many cannabis products sold for dogs list cannabidiol (CBD) instead of THC as the main active ingredient. (THC is the substance in cannabis that typically makes human users high.) Companies selling CBD-predominant substances for dogs may claim that their products are “completely safe” but research is limited to officially back those claims. There are, in fact, many potentially helpful chemicals in the cannabis plant, CBD usually outnumber the rest, although amounts are dependent on the strain of plant. What that means is that the ratio of cannabinoids (i.e., chemicals in the cannabis plant) differs among plants based on their genetics. While the CBD in cannabis does not make someone “high” in the usual sense, it may benefit human patients with various medical problems, including Crohn’s disease, post-traumatic stress disorder and multiple sclerosis. CBD reduces pain, inflammation and anxiety as well as seizure activity. Research suggests that CBD has lower toxicity and higher tolerance than THC in both humans and non-humans. However, research has not yet established safe dosing guidelines for either population, partly because of highly restrictive federal laws that prohibit scientists from thoroughly investigating its effects.

**Warning**  CBD lacks rigorous scientific evidence, which is why veterinarians cannot determine safe dosages and CBD ratios of hemp oil for dogs, cats and other animals. Veterinarians and owners rely on anecdotal reports, trial and error and company claims. If the tolerable and safe dose, whatever that might be, is exceeded, an animal may land in the local veterinary emergency clinic.



Effective therapeutic cannabis doses have not been worked out in pets. It is best to start with the lowest amount possible and to gradually increase the dose every 5 days or so until the desired effect is seen. If undesired side effects such as excessive sedation, disorientation, excitement, vomiting etc. are observed, the cannabis dose is too high and administration should stopped immediately. After the side effects have worn off, the animal can be restarted at a lower dose. The upper oral dose limit for CBD products recommended by veterinarian Dr. Robert Silver is around 1 mg/kg/day orally, but one should start with a much smaller fraction of this dose such as 0.05 mg/kg/day. For THC products, Dr. Silver recommends to start with an oral dose of 0.1-0.25 mg/kg THC once or twice daily. Once the pet has received the same dose over about 1 week without undesired effects, the pet has developed a tolerance and the dose can be gradually increased.

How to calculate your pet's starting dose?

Example 1: Commercial CBD oil

Let's say your dog weighs 55 lb = 25 kg (55÷2.2) and the hemp oil you bought lists 200 mg of CBD infused in 1 oz olive oil. Your dog's starting dose of 0.05 mg/kg/day calculates as 1.25 mg/day (25 kg x 0.05 mg). One fluid ounce equals approximately 30 ml, so the hemp oil has a CBD content of 6.7 mg/ml (200÷30). Your dog's starting dose of 1.25 mg equals a volume of approximately 0.2 ml of the hemp oil (1.25÷6.7). Since olive oil contains approximately 20 drops per ml, 0.2 ml equal about 4 drops (0.2x20). Your starting dose is 4 drops by mouth once daily for 5 days.

Example 2: Home-made Cannabis Oil

Let's say you want to make an herbal oil infusion of the dried cannabis flowers and leaves you bought legally at a dispensary. A strain with a CBD content of 15% and a THC content of 20% contains 150 mg CBD and 200 mg THC, respectively, per one gram of plant material. If you infuse 5 gram of this strain in 200 ml of olive oil using the double-boiler method, your oil will contain 750 mg CBD and 1000 mg of THC, or 3.75 mg/ml CBD and 5 mg/ml THC. Assuming your cat weighs 11 lbs (5 kg), her starting dose of 0.1 mg/kg/day equals an oral dose of 0.5 mg per day. Since each ml of your oil infusion contains 5 mg THC your cat's starting dose is 0.1 ml or approximately 2 drops by mouth once daily for 5 days.

Example 3: Cannabis of Undetermined Potency

Start with the smallest possible amount. Depending on your pet's weight that may be as low as 1 drop or 1 capsule once daily. Observe for undesired effects such as loopy behavior or sedation and if none is observed continue the same dose for 5 days before gradually increasing the dose to desired effect.