Cannabidiol (CBD) oil and pets

Cannabidiol (CBD) is one of many substances (collectively called cannabinoids) that occur naturally in the cannabis plant. Cannabis has traditionally been used by humans for its psychoactive effects, which are mainly due to the cannabinoid delta-9-tetrahydrocannabinol (THC). There is a now a lot of interest in studying the effects of cannabinoids, particularly CBD, in the management of pain and other conditions such as epilepsy in humans and in animals, particularly dogs.

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The cannabinoid substances that are produced naturally by cannabis plants have been found to be similar to substances that occur naturally in mammals, and these have become known as endocannabinoids. This discovery has led to the idea that humans and other mammals have an endocannabinoid system that is involved in controlling normal body systems. However, the exact role of endocannabinoids in the body is not yet clear. They appear to be involved in various bodily functions, including the control of appetite, mood and pain perception. How CBD might work, for example to relieve pain or treat epilepsy, is not yet clear.

There have been a few published trials of CBD in dogs with osteoarthritis. However they have been small, with several limitations and so far there is no clear evidence of a benefit from using CBD in dogs with osteoarthritis.

If CBD is effective in relieving pain in dogs, we do not yet know the optimum dose and we know very little about the side effects, except that in the published clinical trials vomiting occurred in a few dogs and liver enzymes were raised in a high proportion of dogs while on CBD in two separate trials for epilepsy and osteoarthritis. In humans, CBD is broken down by liver enzymes and so there is a potential for drug interactions, but whether the same applies to dogs is not known. CBD interferes with a liver enzyme called CYP3A4 which is the enzyme responsible for metabolizing about 60% of the drugs used in humans. It is reasonable to assume that CBD might interact with other medicines that affect or are affected by liver enzymes in dogs. So CBD could lead to higher or lower than usual blood levels of a co-administered drug leading to changes in levels of efficacy or frequency of side effects or even toxicity.

A liquid formulation of CBD is authorized as a human medicine in the UK (Epidyolex) and the USA (Epidiolex), for the treatment of rare, specific forms of epilepsy. There is a multitude of CBD products marketed as food supplements for humans. There are also many CBD treats marketed for pets. These products are not regulated and not standardized and it is not possible to know what they contain with certainty; studies have shown that the amount of CBD in unregulated products can vary from that declared on the label. Varieties of cannabis plant that contain very little cannabinoids have been cultivated for their seed and fiber and to have low levels of THC. They are often referred to as hemp or industrial hemp. These, and the oil derived from seeds, are found in some herbal products. They may contain little or no CBD.

Under veterinary laws in the US, products containing CBD are considered to be veterinary medicines. This means that it is illegal for companies to sell, supply or advertise CBD products for pets without a marketing authorization from the regulator. Currently there are no veterinary medicines containing CBD that are authorized for use in animals in the US.

It is illegal to give an animal any CBD product unless it has been prescribed by a veterinarian.

Some veterinary medical boards have advised veterinarians against prescribing CBD for pets due to the lack of sufficient clinical trials and currently illegal status of those products for use in animals.