Recently in the Vet Record there was a bold title! ‘Pot for pets: group launched to promote cannabis use‘: a new veterinary group interested in promoting the ‘appropriate and safe use of medicinal cannabis in pets’ has been launched in the USA. It is very exciting, so why isn’t every UK veterinary profession rushing to sell you some natural CBD from the cannabis plant to help heal and cure our pets?

The answer has many answers, so here is my low down on the idea of ‘pot for pets’. 

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Reason One: Legislation

CBD classed as veterinary medicine by the medicines regulator, the VMD:

‘We consider that veterinary products containing Cannabidiol (CBD) are veterinary medicines and should be regulated as such.’

CBD products for use in animals therefore now require a marketing authorisation before they can be sold or supplied in the UK. There are currently no CBD based products that have been granted a UK veterinary marketing authorisation.

There is currently NO licensed animal medicine containing CBD licensed in the UK, and the regulatory and legislative framework for a veterinary surgeon to prescribe CBD is extremely difficult. 

Reason Two: Side effects

Owners appear to see CBD as a natural product and therefore ‘safe’; one study stated that the positive attitude towards the safety and efficacy of CBD was attributed to it being a natural product.

In a few studies there have been changes in liver function, the mechanism for this is not yet known; however, it could be due to toxicological response or adaptative response as return to normal alkaline phosphatase (ALP) levels were seen after treatment was ceased. Several possibilities exist to explain the potential mechanisms for the ALP elevation, including hepatotoxicity, specific enzyme induction and generalised microsome induction, all of which require further investigation.

The Committee on Toxicology (2020) stated:

‘Based on the available in vitro and in vivo data, CBD appears to have the following adverse effects: hepatotoxicity, immunotoxicity, reproductive toxicity, and interactions with drug metabolizing enzymes (P450), suggesting a risk to consumers. In addition, the effects on drug metabolizing enzymes following CBD exposure indicate the potential for drug interactions between CBD and pharmaceutical drugs.’ 

It is therefore important to understand that just because it is marketed and appears ‘natural’, does not make it safe or without side effects. If it has the potential to impact parts of our body systems or our pet’s body systems, it also has the potential to impact them positively and negatively.  

Reason Three: Product Quality Concerns

Research has shown that most owners are buying online, without realising this is in breach of legislation – this is very worrying. 

There is potential for counterfeit products being used by owners as “over-the-counter” products have proved to have unreliable contents. The Centre for Medicinal Cannabis (2019) stated laboratory tests found 62% of the UK high street products studied did not contain the CBD content on the label and 37% contained high levels of THC (Consumer CBD products Working Group, 2020). 

In the human health care field, the Food Standards Agency (FSA) have been working on this worrying trend in poor quality products:

‘The novel food status of CBD was confirmed in January 2019. That is why CBD food products require authorisation before they can be sold legally in Great Britain (GB).

Novel foods, like CBD food products, must be authorised before they are put on the market to ensure they have been through an independent safety assessment.’

Even in human health care, they are learning more and more about side effects and making changes to recommendations, bearing in mind that animal literature is still miles behind human literature, this could be a forecast for what we see in veterinary medicine too. Earlier in October 2023, the UK Food Standards Agency (FSA) issued updated precautionary advice on CBD, which recommended that “healthy adults should limit their consumption of CBD from food to 10mg per day, which is about 4-5 drops of 5% CBD oil.” The previous limit was 70 mg per day. This change in advice is based on new evidence from the industry and advice from FSA’s independent scientific committees.

Reason Four: Evidence Base

We have some great studies coming out, which help guide us, but the results still have some downfalls, which is why we aren’t all singing and dancing about CBD as the ‘miracle cure’ that it is often marketed as. 

In one study investigating osteoarthritis, pain and activity scores showed a significant decrease in pain and increase in the dog’s activity with the CBD oil in a study by Gamble et al. (2018). However, important considerations need to be considered to make this claim for long term OA treatment. Firstly, there were some downsides to the study, namely the study length (4 weeks) and sample size. Sample size was certainly a problem; 22 client-owned dogs were recruited. Only 16 of these dogs completed the trial and were included in the analyses. Longer study duration or the gathering of field data would help ascertain the long-term effects of CBD use.

What did they find?

McGrath et al. (2019) found dogs in the CBD group had a significant, median change, reduction in seizure frequency, compared with the placebo group, plasma CBD concentrations were correlated with reduction in seizure frequency. However, the proportion of dogs considered responders to treatment (≥ 50% decrease in seizure activity) was similar between groups. Again, study size was a huge downfall; only 9 dogs in the CBD group and 7 in the placebo group were included in the analysis.

A study by Mejia et al. (2021) evaluating the effect of cannabidiol on naturally occurring osteoarthritis-associated pain in dogs found there were no differences noted between groups at any time point for any of the recorded outcome measures. Adverse events associated with CBD administration included elevation in liver enzymes in 14 dogs and vomiting in 2 dogs.

In one meta-analysis by Barbeau-Grégoire et al. (2022) the results suggested that CBD has promising effects, however further investigation is needed to determine the efficacy, doses, formulations and combinations recommended for the treatment.

Overall, although promising there is still not enough information to draw strong conclusions.

Conclusion

CBD is always a bit controversial; owners generally are frustrated at why veterinary professionals may seem a little dismissive of the idea. But please rest assured that it is because of all the above reasons. CBD is not a miracle cure, it may help some conditions, and we will understand more about this as we get more robust data. You must not give CBD without telling your vets or a prescription in the UK. Currently, regulatory constraints, lack of evidence, and possibility of side effects, interactions with treatment plans and inappropriate products being used, veterinary professionals are certainly right to refrain from making an opinion on this popular substance! 

References and Further Reading