Now that recreational use of cannabis is legal in Oregon many pet guardians wonder about whether using this plant may be beneficial for their pet’s ailments and they turn to their veterinarians for advice. However, many Oregon veterinarians will not be able or willing to give any advise on medicinal use of cannabis due to lack of knowledge about herbal medicine or because they are afraid of possible negative legal implications.

Even though recreational marijuana use is legal in Oregon, it is still classified as a Schedule I controlled substance by federal law and the Drug Enforcement Agency (DEA) and illegal for all veterinarians to prescribe to their patients. Medical marijuana laws do not apply to veterinarians, only to human physicians and their patients. This is a dilemma for veterinarians and their clients because here in Oregon humans can now legally share their “stash” with their pets within the limitations of potential animal abuse complaints. The Oregon Veterinary Medical Examining Board (OVMEB) currently advises veterinarians under its jurisdiction to use caution in discussing marijuana use with their clients. Potential complaints by the public about marijuana use in specific veterinary patients could be reviewed by the OVMEB as a non-justified, non-standard treatment and the veterinarian involved could face disciplinary action by the board. Oregon veterinarians recommending medicinal marijuana for a specific patient are required to get written client consent.

Hemp vs. Marijuana
There are two main cultivars of Cannabis sativa L., non-psychotropic hemp (high in fiber and CBD, low in THC) and psychotrophic marijuana (high THC content). All parts of the cannabis plant have been used for fiber and food by humans since prehistoric times. Cannabis contains hundreds of phytochemicals, and medicinal use of the plant was first mentioned in 2700 BC in the pharmacopeia of Emperor Shen Nung, the father of Traditional Chinese Medicine. Tea from cannabis was prescribed for many different ailments and a combination of alcohol and cannabis was used as an analgesic by Chinese physicians. The therapeutic benefits of phytocannabinoids such as THC and CBD, as well as other phytoconstituents stem from the interactions of these compounds with each other. Different strains of Cannabis sativa L. contain different combinations of these phytochemicals and hence differ in their medicinal benefits.

The body’s endocannabinoid system with it’s CB1 and CB2 receptors fulfills a major function in maintaining homeostasis within the body (relax, eat ,sleep, forget and protect) and is involved in neural activity, pain, memory, emotion, carcinogenesis, and embryonic development. THC binds primarily to CB1 receptors and of all mammals studied, dogs have the highest concentration of these receptors, particularly in brain areas related to coordination. Hence, dogs are more sensitive to THC than other mammals (including humans) and when given too much of THC develop “static ataxia”, a condition where the animal is swaying from side to side, drooling, urinating on itself and acting disoriented.

Therefore, and in dogs in particular, the low-THC hemp plant is much safer to use in pets than the high-THC marijuana strains. Some herbalists believe that hemp may be medicinally superior to marijuana because it is botanically closer to the original plant used for medicinal purposes thousands of years ago, before it became popular to breed high-THC strains for recreation. In our clinic, we have seen beneficial therapeutic results in our patients using CBD products derived from industrial hemp, particularly in pets with arthritic pain and anxiety issues. Other conditions that could benefit from cannabis include seizures, inflammation, dermatitis, cancer and behavioral problems.

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.

Example2: 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.
For more information on how to make an herbal infusion see instructions below.

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.

It is safer to use legal industrial hemp products for pets since they contain nearly no THC and have high amounts of medicinally valuable CBD and other nonpsychotropic cannabinoids, terpenes and terpenoids. There is risk of toxicity and expensive emergency visits if your pet is given too much THC or gets accidentally into marijuana products. Be aware, that many edible cannabis products for humans contain ingredients toxic to pets, such as xylitol, macademia nuts and chocolate. There have been two cases reported in the literature of dogs dying from marijuana, both of these dogs ingested cannabis products containing chocolate, which appears to have a negative cumulative toxic effect. Always keep our own edibles and your pets’ cannabis products safely stored away from pets and children.

References & Resources
Cannabis sativa L: Its Botany and Potential Value to Veterinary Medicine. VBMA Teleseminar July 2015. Robert J. Silver DVM, MS, CVA